Int J Gynecol Obster, 1992, 39: 211-283
217
International Federation of Gynecology and Obstetrics
Maternal weight, weight gain during pregnancy and pregnancy outcome U. Ekblad and S. Grenman Department of Obstetrics and Gynecology, University of Turku, Turku (Finland)
(Received February 27th, 1992) (Revised and accepted June 17th, 1992)
Abstract OBJECTIVE: To evaluate the effects of abnormal maternal weight or weight gain on pregnancy outcome. METHOD: Records for 191 mothers with abnormal prepregnancy weight ( L 200A) above, or under, ideal body weight for height) or weight gain ~20 kg, or 15 kg during pregnancy were reviewed. The control group ccnsisted of 166 mothers with normal prepregnancy weight and normal weight gain during pregnancy. Data on mothers and their infants were analyzed by one-way analysis of variance. RESULTS: Obese women and mothers with excessive weight gain duringpregnancy had an increased incidence of induced labor (P I 0.05) and tendency for emergency cesarean sections during the delivery. Obese women had more large-for-date babies than controls (P I 0.05). Weight gain 15 kg during pregnancy was most common in slightly obese women and did not carry any special obstetric or neonatal risk. Underweight women had a significant risk for delivering a small-fordata baby. CONCLUSION: Obese women and women with excessive weight gain during pregnancy need special follow-up and counseling during pregnancy and delivery. Underweight women may need prepregnancy nutritional counseling to guarantee normal fetal growth. In developed countries suboptimal weight gain (I 5 kg) during pregnancy seems not to need any medical intervention.
0020-1292/92/305.00 0 1992 International
Federation of Gynecology and Obstetrics Printed and Published in Ireland
Keywords: Pregnancy; weight gain.
Obesity;
Abnormal
Introduction Obesity is one of the most prevalent diseases in developed countries [ 11. On the other hand, the modem standard of feminine beauty is a slim, prepubescent figure, which often is unobtainable without vigorous exercise and dieting. In extreme cases this can lead to insufficient nutrition. These nutritional disorders have been reported to have adverse effects on the health and well-being of a pregnant woman and her fetus [7,8,10-121. Also, excessive or suboptimal weight gain during pregnancy have been suggested to increase perinatal and obstetric morbidity [ 141. This study was performed to evaluate the effects of abnormal maternal weight and weight gain on pregnancy outcome in Finnish parturients. Patients and methods Turku University Central Hospital serves as the regional tertiary care perinatal center for the southwestern part of Finland. There are over 5000 deliveries per year in this region. The delivery room log books contain a record of each pregnancy and delivery and also data on the neonate. These data, retrospectively, together with prepregnancy weight, as well as height and weight at Article
278
Ekblad and Gremnan
delivery, prospectively, were collected from all 1172 mothers giving birth at our institution during the 6-month study period starting July Ist, 1985. The study population consisted of 191 mothers and their neonates selected because of the abnormal maternal prepregnancy weight or abnormal weight gain during pregnancy: prepregnancy weight ~20% over, or under, ideal body weight for height, or weight gain of L 20 kg, or I 5 kg during pregnancy. The next mother in sequential order with normal prepregnancy weight and weight gain during pregnancy served as a control (n = 166). Maternal characteristics are presented in Table 1. The collected data was analyzed as follows: each of the four study groups were separately compared with the control group by means of the one-way analysis of variance, in order to detect any differences between the group means. The equality of variances in the groups in question was tested by Levene’s test, and whenever equality could not be assumed, the Welch statistic was computed and employed in the subsequent analyses instead of the F statistic. A Shapiro-Wilke Wtest was run for each variable to detect whether it fulfilled the normality assumption
required by the analysis of variance. For those variables that could not be assumed to be normally distributed, the analyses were based on the nonparametric Kruskal-Wallis one-way analysis of variance. The data were analyzed using the BMDP2D, BMDP7D and BMDP3S programs. RtXWltS Pregnancy outcome
Data on pregnancy length, birthweight and estimation of birthweight in all weight subgroups is presented in Table 2. The majority of the mothers went into labor at term and there were no postmature (longer than 42 gestational weeks) pregnancies. In the control group the average birthweight was 3538 f 535 g (mean f SD). Obese women and women with excessive weight gain during pregnancy (subgroups I and IV) had heavier babies than control mothers (P < 0.05, P c 0.005, respectively). Women who were ~20% underweight prior to pregnancy (II) had significantly smaller babies (P < 0.05) than controls. In the group of mothers with weight gain I 5 kg during pregnancy (III) the average birthweight was 3284 * 880 g. However, these numbers did
Table 1. Maternal characteristics. Weight category I
II
III
IV
V
2 20% under normal weight for height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
n
2 20% over normal weight for height 77
30
56
166
Age (years) Ht. (cm) Wt. (kg) BMI (kp/m’) Wt. gain (kg) Wt. at delivery (kg) Prior deliveries
28 f 166 f 83.9 f 39.5 * 11.8 f 95.5 zt 1.0 *
25.5 zt 165 f 46.7 + 17.2 zt 13.4 f 60.3 zt 0.8 zt
29.5 f 167 f 73.1 f 26.1 zt 3.0 f 76.2 f 1.2 *
28.7 f 4.7 166 f 5.3* 65.0 f 12.2*** 23.6 f 4. I*** 23.2 f 22.8*** 88.0 f 12.5*** 0.8 zt 1.0
28.7 + 4.4 164 ?? 5.3 58.3 + 6.5 21.6 f 2.0 13.2 f 3.4 71.4 f 6.9 0.9 ?? 1.0
5.1 5.3’ lO.l*** 3.4*** 6.2* 11.6*** 1.0
5.1*** 5.8 3.4**+ 0.9*+* 4.5 5.8*“* 0.8
5.1 4.6** 16.5*** 6.1*** 3.5*** 15.9*** 1.1
Data represent mean f SD, study groups compared with the control group. *P < 0.05; **p < 0.005; ***p < 0.0005. Ht. (height), Wt. (weight), BMI (body mass index = weight (kg)iheight (m’). Int J Gynecol Obstet 39
Maternal weight, abnormal weight gain and perinatal outcome
TabIe 2.
279
Gestational weeks at birth, estimation of fetal size and actual birthweight. Weight category
n Gestational weeks at delivery Birthweight (g) 1. Ultrasound estimation (g) at 36-31 weeks 2. Manual estimation (g) at delivery SF height (cm) At 24 weeks At delivery
I
II
III
IV
V
2 20% over normal weight for height 17
h 20% under normal weight for height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
30
56
166
38.7 f 2.1
39.6 zt 1.2
31.6 f 3.5
39.1 f 1.6
38.9 f 2.0
3712 f 614*
3293 f 362*
3284 f 880
3803 f 538;;
3538 f 535
3463 f 131*
2707 zt 505*
3256 f 153
3845 f 436**’
3047 f 568
3782 + 327++*
3183 zt 313***
3481 zt 517
3881 zt 960***
3497
21.8 f 2.6 34.0 f 3.6**
19.9 zt 1.6*** 31.9 f 3.0
21.2 ?? 2.0 30.8 + 4.0;
21.1 f 2.5 35.0 ?? 3.9***
21.2 f 2.5 32.8 f 3.4
?? 363
Data represent mean ?? SD, study groups compared with control group. SF height, symphysis-fundus height. *P < 0.05; **p < 0.005; ***p < 0.0005.
not statistically differ from the control group probably due to wide standard deviation. The accuracy of estimation of fetal size by ultrasound and manual palpation is presented in Table 2. The ultrasound estimation of fetal size was performed at 36-37 gestational weeks and the manual estimation in the delivery room. Both techniques predicted well the actual birthweight in all weight groups. Fetal growth was also followed by serial symphysis-fundus (SF) height measurements. At 24 gestational weeks SF height in the control group was 21 ??3 cm (mean f SD) and at delivery 33 * 3 cm. Lean mothers (II) had significantly shorter SF height already at 24 weeks than control mothers (P < 0.0005) and they also gave birth to significantly smaller babies than controls (P < 0.05). At delivery obese women (I) and mothers with excessive weight gain (IV) had higher SF height than control mothers (P < 0.005 and P c 0.0005, respectively). These mothers also gave birth to heavier babies than controls, as reported above.
Management and outcome of delivery
Data on labor is presented in Table 3. The rate of labor induction in the control group was 24%. Induced labor was more common in the group of obese mothers and mothers with excessive weight gain than in the control group (36% vs. 43%, P c 0.05). Over 70% of control group mothers had normal vaginal delivery, 5% assisted vaginal delivery and 22% cesarean section (CS). The incidence of vaginal breech delivery was 2%. Mothers with weight gain I 5 kg during pregnancy had more normal vaginal deliveries than controls (90% vs. 70%, P < 0.05). Mothers with excessive weight gain during pregnancy had the lowest rate of normal vaginal deliveries (64O), the highest rate of assisted vaginal deliveries (13%) and the highest rate of CS (23%) most of them emergency CS. However, these numbers did not statistically differ from the control group, maybe because of low number of cases. Also, obese mothers with high initial body mass index (BMI) had a high rate of CS (21%) Article
280
Ekblad and Gremnan
Table 3.
Management and outcome of delivery. Weight category I
II
III
IV
V
2 20% over normal weight for height
Weight gain 55 kg
Weight gain 220 kg
Control group
30
56
166
n
71
~20% under normal weight for height 28
Induction of labor (%) Mode of delivery (%) Normal vaginal Forceps or vacuum Breech CS (elective)
36*
25
23
43;
24
78 1 0 7 21% 14
88 0 4 4 8% 4
90* 3 1 3 6% 3
64 13 0 5 23% 18
71 5 2 13 22% 9
300 ~296 17 ?? 15 ll* 6 0
333 f 208 15 zt 18* 13 ?? 13 3
374 zt 208 21 + 25 l3* 11 2
346 f 188 21 f 18 12 ?? 12 0.6
CS (emergency) Labor pattern I stage (min) 311 f 203 II stage @in) 18 f 17 III stage (mitt) 21* 11 Shoulder dystocia (%) 3 Vaginal repair (%) II0 0 1110 0
0 0
4 0
5 0
2 0
Data represent mean f SD, study groups compared with the control group. *P < 0.05; **p < 0.005. CS, cesarean section.
mostly emergency CS during the delivery. Lean women (II), as well as women with weight gain I 5 kg (III), had the lowest rate of CS, 8% and 6%, respectively. The numbers did not reach statistical significance compared with the control group. There were no statistical differences in the length of first and third stage of labor between study and control groups. The second stage of labor was shortest in the group of women with weight gain I 5 kg during pregnancy (P < 0.05). The overall incidence of shoulder dystocia was low: in the control group 0.6%, in the group of lean mothers (II) 0% and in other subgroups 2-3%. There were no statistical differences between the study and control groups. Vaginal lacerations were uncommon in the study group and there were no statistical differences between study and control mothers Int J Gynecol Obstet 39
in the rate of repair of second or third degree lacerations. Neonatal outcome
Table 4 summarizes the overall neonatal outcome in different subgroups. Obese mothers (I) and mothers with excessive weight gain during pregnancy (IV), gave birth to considerably heavier babies than controls (P < 0.05, P < 0.005). The sex ratio was similar in all subgroups (> 50% females) and so, did not have any effect on the birthweight difference between groups. There were more large-for-gestational age babies in the group of obese (I) mothers than in the control group (P < 0.05). Lean mothers (II) delivered smaller babies than controls (P < 0.05) and the number of SGA babies was significantly higher (P < 0.0005) than in the control group. In the
Maternal weight, abnormal weight gain ana’perinatal outcome
Table 4.
281
Neonatal outcome. Weight category I
II
III
IV
V
zr 20% under normal weight to height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
n
220% over normal weight to height 17
30
56
166
Birthweight (g)
3712 f 614:
3294 zt 362*
3284 f 880
3803 f 538’;
3538 f 535
Weight percentile (%) c2.5 2.5-10 10-50 50-90 90-97.5 >97.5 Apgar score 1’ 5’ 10’ Umbilical vein astrup n PH PC02 PO2
Admitted to NICU n = (%) Hyperbilirubinemia n (%) PNM n (%)
** b
*a
??
0
1 6 35 43 13 2
25 41 17 9
4 18 63 11 4 0
3 14 32 34 14 3
2 42 29 20
8.4 f 1.5 8.8 f 1.1 8.8 f 1.1
8.8 ?? 0.7 9.0 f 0.6 9.0 + 0.6
8.2 z+z1.8 8.5 zt 1.8 8.6 zrz1.8
8.2 f 1.7 8.8 zt 0.6 8.9 zt 0.5
8.6 ?? 0.7 8.9 f 0.6 9.0 f 0.5
29 7.32 f 0.08 5.55 f 1.17 2.98 f 0.81
13 7.31 ?? 0.07 5.78 zt 1.04 2.66 f 0.71
12 7.32 zt 0.09 5.40 zt 1.06 2.93 zt 0.98
27 7.30 ?? 0.10 5.98 f 1.35 2.83 f 0.88
68 7.32 ztz0.0 5.89 zt 10.0 2.91 ZL0.8
2 (3%)
1 (4%)
0
1 (2%)
3 (2%)
12 (18%)
1 (4%)
3 (10%)
3 (5%)
14 (9%)
1 (1%)
0 (0%)
2 (7%)
0 (0%)
2 (1%)
1
I
7
Data represent mean f SD, study groups compared with the controls. NICU, neonatal intensive care unit; PNM, perinatal mortality. *P < 0.005; ***p < 0.0005. *P < 0.05; ?? *asigniflcantly more babies over 90th percentile. ?? **bsigniticantly more babies under 10th percentile.
group of mothers with weight gain less than 5 kg during pregnancy the average birthweight was lower and the percentage of SGA babies was higher than in the control group. *Thedifference was statistically not significant, maybe due to wide standard deviation in the birthweight and small number of SGA babies generally. Neonatal outcome expressed as Apgar scores and umbilical vein blood gas values at birth was equally good in all subgroups. There were no severely asphyxiated babies at birth in this study. The rates of admission to
the neonatal intensive care unit (NICU), of neonatal hyperbilirubinemia and of perinatal mortality did not significantly differ between study and control groups. Discussion Both maternal underweight [2] and obesity [7,10] as well as abnormal weight gain [2] during pregnancy have been reported to increase obstetric risks [15]. In our study the incidence of prepregnancy underweight (BMI 17.2 & 3.4 kg/m2, Article
282
Ekblad and Grenman
~20% under normal weight for height) was 2.4% and that for obesity (BMI 39.5 f 3.4 ks/m*, ~20% above normal weight for height) 6.6%. The incidence of subnormal (s 5 kg) or excessive weight gain (220 kg) during pregnancy was 2.6% and 4.8%, respectively. Similar incidences have been reported from other developed countries [3,12]. In the control group the average prepregnancy weight, BMI and weight gain during pregnancy were 58.3 f 6.5 kg, 22 f 2 kg/m2 and 13 f 3 kg, respectively. In general, obese women gained less weight during pregnancy than did mothers with normal or lean stature. In fact, women with extremely low weight gain during pregnancy (I 5 kg) carried on average 15 kg overweight prior to pregnancy (BMI 26.1 A 6.1 kg/m2), as has been reported also by other groups [3,6]. The highest risk for excessive weight gain (220 kg) during pregnancy was in the group of women with some obesity prior to pregnancy (BMI 23.6 f 4.1 kg/m2). This group of pregnant women identified may need special nutritional counseling during the visits to antenatal care centers. In our study parity did not have any significant effect on weight gain during pregnancy. This is in contrast to earlier studies reporting that high parity goes together with excessive weight gain during pregnancy [6,14]. The discrepancy could be explained by overall low parity in our study. Brown et al. [2] have reported that underweight women have an increased risk for premature deliveries. In this study the percentage of premature deliveries was similar in study and control groups and thus, maternal prepregnancy weight or abnormal weight gain during pregnancy did not affect the gestational length. Our results are in agreement with the data from Frantzen and coworkers [6] and indicate that underweight women have an increased risk of delivering a SGA baby, but not a premature one. In this study, the actual birthweight increased with maternal pregnancy weight gain as also reported from Sweden [13]. Also, exInt J Gynecol Obstet 39
tremely obese women prior to pregnancy had significantly heavier babies than controls, which is in contrast to results of other studies [6,13], where maternal obesity did not increase the actual birthweight. Measuring the symphysis-fundus height is a cost-free and readily available method of estimating fetal size [9]. The usefulness of measuring SF height seems to be independent of maternal prepregnancy weight and weight gain during pregnancy as shown in our study. Short SF height measured at 24 weeks of gestation predicts well an inherited small or intrauterine growth retarded, SGA, baby. In our study, obese women and women with excessive weight gain during pregnancy were more likely to undergo induction of labor than controls. Similar results are reported by other authors [4]. In these weight groups frequent induction of labor may be performed to prevent large-for-date babies. Furthermore, a tendency of increased number of emergency CSs during the labor was seen, if the mother was obese or had excessive weight gain during pregnancy, as suggested also by other authors [4]. In contrast, mothers with weight gain I 5 kg during pregnancy had more spontaneous, normal vaginal deliveries than mothers in the control group. They also had on average smaller babies than controls, which may explain the easier course of delivery. The effect of physical activity during pregnancy was not tested in our study, but it is possible that women with low weight gain during pregnancy were physically more active than mothers in the control group. Good physical condition has been shown to have a positive effect on the course of delivery [5]. A prospective study is needed to evaluate the effect of physical exercise on pregnancy, labor and the newborn in different weight and weight gain subgroups. The rate of CSs is high in most of the developed countries. In our hospital the percentage of CSs during the study was 22% in the control group. Obese women and women with excessive weight gain during pregnancy had a CS rate of 21% and 23%,
Maternal weight, abnormal weight gain and perinatal outcome
respectively. In contrast, underweight women and women with poor weight gain during pregnancy had a CS rate of 8% and 6%. In conclusion, our results indicate that obesity and excessive weight gain during pregnancy carry an increased risk for complications during the delivery. These mothers need special follow-up and counseling during the and delivery. Furthermore, pregnancy underweight women have an increased risk of delivering a SGA baby; they may need prepregnancy nutritional counseling and special follow-up to prevent intrauterine growth retardation. In this study mothers with low weight gain during pregnancy were moderately overweight prior to pregnancy and maybe therefore, low weight gain was not a maternal or neonatal risk factor. Strict recommendations for optimal weight gain during pregnancy seem not to be necessary in developed countries. Neonatal outcome in all weight groups was equally good indicating that the classical risk factors associated with abnormal weight or weight gain prior to and during pregnancy can be controlled with readily available antenatal care and modem obstetric management.
4
5
6
7
8 9
10 11
12 13 14
15
283
Dougherty CRS, Jones AD: Obstetric management and outcome related to maternal characteristics. Am J Obstet Gynocol 158: 470, 1988. Erkkola R: The physical work capacity of the expectant mother and its effect on pregnancy, labor and the newborn. Int J Gynecol Obstet 14: 153, 1976. Frantzen B, Dimperio DL, Gruz AC: Maternal weight gain; Effect on infant birth weight among overweight and average-weight low income women. Am J Obstet Gynecol 259: 1114, 1988. Garbaciak JA Jr, Richter M, Miller S, Barton JJ: Maternal weight and pregnancy complication. Am J Obstet Gynecol 152: 238, 1985. Gross T, Sokol RJ, King KG: Obesity in pregnancy: Risk and outcome. Obstet Gynecol 56: 446, 1980. Hughes AB, Jenkins A, Newcombe RG, Pearson JF: Symphysis fundus height, maternal height, labor pattern and mode of delivery. Am J Obstet Gynecol 75: 156, 1987. Kliegman RM, Gross T: Perinatal problems of the obese mother and her infant. Obstet Gynecol 66: 299, 1985. Metzger B, Freinkel N: Accelerated starvation in pregnancy: Implications for dietary treatment of obesity and gestational diabetes mellitus. Biol Neonate 51: 78, 1987. Ruge S, Andersen T: Obstetric risk in obesity. An analysis of the literature. Obstet Gynecol Surv 40: 57, 1985. RBssner S, &lin A: Maternal body weight and relation to birth weight. Acta Obstet Gynecol Stand 69: 475, 1990. Shepard MJ, Hellenbrand KG, Bracken MB: Proportional weight gain and complications of pregnancy, labor and delivery in healthy women of normal prepregnant stature. Am J Obstet Gynecol 155: 947, 1986. Winick M: Nutrition, Pregnancy and Early Infancy, p 3. Williams and Wilkins, Baltimore, 1989.
References Albrink MJ: Obesity. In: Textbook of Medicine (eds PB Benson, W McDermott), p 1375. W.B. Saunders Company, Philadelphia, 1975. Brown JE, Jakobson HIV, Askue LH, Peick MG: Influence of pregnancy weight gain on the size of infants born to underweight women. Obstet Gynecol57: 13,198l. Calandra C, Abel1 DA, Beicher NA: Maternal obesity in prenancy. Obstet Gynecol 57: 8, 1976.
Address for reprintst
U. Ekblad and Gpeeology DepamntofobstcMcs Turku Univ~ Central Hospital -Ym 4-5 20!52JlTurka, Finlad
Article
217
International Federation of Gynecology and Obstetrics
Maternal weight, weight gain during pregnancy and pregnancy outcome U. Ekblad and S. Grenman Department of Obstetrics and Gynecology, University of Turku, Turku (Finland)
(Received February 27th, 1992) (Revised and accepted June 17th, 1992)
Abstract OBJECTIVE: To evaluate the effects of abnormal maternal weight or weight gain on pregnancy outcome. METHOD: Records for 191 mothers with abnormal prepregnancy weight ( L 200A) above, or under, ideal body weight for height) or weight gain ~20 kg, or 15 kg during pregnancy were reviewed. The control group ccnsisted of 166 mothers with normal prepregnancy weight and normal weight gain during pregnancy. Data on mothers and their infants were analyzed by one-way analysis of variance. RESULTS: Obese women and mothers with excessive weight gain duringpregnancy had an increased incidence of induced labor (P I 0.05) and tendency for emergency cesarean sections during the delivery. Obese women had more large-for-date babies than controls (P I 0.05). Weight gain 15 kg during pregnancy was most common in slightly obese women and did not carry any special obstetric or neonatal risk. Underweight women had a significant risk for delivering a small-fordata baby. CONCLUSION: Obese women and women with excessive weight gain during pregnancy need special follow-up and counseling during pregnancy and delivery. Underweight women may need prepregnancy nutritional counseling to guarantee normal fetal growth. In developed countries suboptimal weight gain (I 5 kg) during pregnancy seems not to need any medical intervention.
0020-1292/92/305.00 0 1992 International
Federation of Gynecology and Obstetrics Printed and Published in Ireland
Keywords: Pregnancy; weight gain.
Obesity;
Abnormal
Introduction Obesity is one of the most prevalent diseases in developed countries [ 11. On the other hand, the modem standard of feminine beauty is a slim, prepubescent figure, which often is unobtainable without vigorous exercise and dieting. In extreme cases this can lead to insufficient nutrition. These nutritional disorders have been reported to have adverse effects on the health and well-being of a pregnant woman and her fetus [7,8,10-121. Also, excessive or suboptimal weight gain during pregnancy have been suggested to increase perinatal and obstetric morbidity [ 141. This study was performed to evaluate the effects of abnormal maternal weight and weight gain on pregnancy outcome in Finnish parturients. Patients and methods Turku University Central Hospital serves as the regional tertiary care perinatal center for the southwestern part of Finland. There are over 5000 deliveries per year in this region. The delivery room log books contain a record of each pregnancy and delivery and also data on the neonate. These data, retrospectively, together with prepregnancy weight, as well as height and weight at Article
278
Ekblad and Gremnan
delivery, prospectively, were collected from all 1172 mothers giving birth at our institution during the 6-month study period starting July Ist, 1985. The study population consisted of 191 mothers and their neonates selected because of the abnormal maternal prepregnancy weight or abnormal weight gain during pregnancy: prepregnancy weight ~20% over, or under, ideal body weight for height, or weight gain of L 20 kg, or I 5 kg during pregnancy. The next mother in sequential order with normal prepregnancy weight and weight gain during pregnancy served as a control (n = 166). Maternal characteristics are presented in Table 1. The collected data was analyzed as follows: each of the four study groups were separately compared with the control group by means of the one-way analysis of variance, in order to detect any differences between the group means. The equality of variances in the groups in question was tested by Levene’s test, and whenever equality could not be assumed, the Welch statistic was computed and employed in the subsequent analyses instead of the F statistic. A Shapiro-Wilke Wtest was run for each variable to detect whether it fulfilled the normality assumption
required by the analysis of variance. For those variables that could not be assumed to be normally distributed, the analyses were based on the nonparametric Kruskal-Wallis one-way analysis of variance. The data were analyzed using the BMDP2D, BMDP7D and BMDP3S programs. RtXWltS Pregnancy outcome
Data on pregnancy length, birthweight and estimation of birthweight in all weight subgroups is presented in Table 2. The majority of the mothers went into labor at term and there were no postmature (longer than 42 gestational weeks) pregnancies. In the control group the average birthweight was 3538 f 535 g (mean f SD). Obese women and women with excessive weight gain during pregnancy (subgroups I and IV) had heavier babies than control mothers (P < 0.05, P c 0.005, respectively). Women who were ~20% underweight prior to pregnancy (II) had significantly smaller babies (P < 0.05) than controls. In the group of mothers with weight gain I 5 kg during pregnancy (III) the average birthweight was 3284 * 880 g. However, these numbers did
Table 1. Maternal characteristics. Weight category I
II
III
IV
V
2 20% under normal weight for height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
n
2 20% over normal weight for height 77
30
56
166
Age (years) Ht. (cm) Wt. (kg) BMI (kp/m’) Wt. gain (kg) Wt. at delivery (kg) Prior deliveries
28 f 166 f 83.9 f 39.5 * 11.8 f 95.5 zt 1.0 *
25.5 zt 165 f 46.7 + 17.2 zt 13.4 f 60.3 zt 0.8 zt
29.5 f 167 f 73.1 f 26.1 zt 3.0 f 76.2 f 1.2 *
28.7 f 4.7 166 f 5.3* 65.0 f 12.2*** 23.6 f 4. I*** 23.2 f 22.8*** 88.0 f 12.5*** 0.8 zt 1.0
28.7 + 4.4 164 ?? 5.3 58.3 + 6.5 21.6 f 2.0 13.2 f 3.4 71.4 f 6.9 0.9 ?? 1.0
5.1 5.3’ lO.l*** 3.4*** 6.2* 11.6*** 1.0
5.1*** 5.8 3.4**+ 0.9*+* 4.5 5.8*“* 0.8
5.1 4.6** 16.5*** 6.1*** 3.5*** 15.9*** 1.1
Data represent mean f SD, study groups compared with the control group. *P < 0.05; **p < 0.005; ***p < 0.0005. Ht. (height), Wt. (weight), BMI (body mass index = weight (kg)iheight (m’). Int J Gynecol Obstet 39
Maternal weight, abnormal weight gain and perinatal outcome
TabIe 2.
279
Gestational weeks at birth, estimation of fetal size and actual birthweight. Weight category
n Gestational weeks at delivery Birthweight (g) 1. Ultrasound estimation (g) at 36-31 weeks 2. Manual estimation (g) at delivery SF height (cm) At 24 weeks At delivery
I
II
III
IV
V
2 20% over normal weight for height 17
h 20% under normal weight for height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
30
56
166
38.7 f 2.1
39.6 zt 1.2
31.6 f 3.5
39.1 f 1.6
38.9 f 2.0
3712 f 614*
3293 f 362*
3284 f 880
3803 f 538;;
3538 f 535
3463 f 131*
2707 zt 505*
3256 f 153
3845 f 436**’
3047 f 568
3782 + 327++*
3183 zt 313***
3481 zt 517
3881 zt 960***
3497
21.8 f 2.6 34.0 f 3.6**
19.9 zt 1.6*** 31.9 f 3.0
21.2 ?? 2.0 30.8 + 4.0;
21.1 f 2.5 35.0 ?? 3.9***
21.2 f 2.5 32.8 f 3.4
?? 363
Data represent mean ?? SD, study groups compared with control group. SF height, symphysis-fundus height. *P < 0.05; **p < 0.005; ***p < 0.0005.
not statistically differ from the control group probably due to wide standard deviation. The accuracy of estimation of fetal size by ultrasound and manual palpation is presented in Table 2. The ultrasound estimation of fetal size was performed at 36-37 gestational weeks and the manual estimation in the delivery room. Both techniques predicted well the actual birthweight in all weight groups. Fetal growth was also followed by serial symphysis-fundus (SF) height measurements. At 24 gestational weeks SF height in the control group was 21 ??3 cm (mean f SD) and at delivery 33 * 3 cm. Lean mothers (II) had significantly shorter SF height already at 24 weeks than control mothers (P < 0.0005) and they also gave birth to significantly smaller babies than controls (P < 0.05). At delivery obese women (I) and mothers with excessive weight gain (IV) had higher SF height than control mothers (P < 0.005 and P c 0.0005, respectively). These mothers also gave birth to heavier babies than controls, as reported above.
Management and outcome of delivery
Data on labor is presented in Table 3. The rate of labor induction in the control group was 24%. Induced labor was more common in the group of obese mothers and mothers with excessive weight gain than in the control group (36% vs. 43%, P c 0.05). Over 70% of control group mothers had normal vaginal delivery, 5% assisted vaginal delivery and 22% cesarean section (CS). The incidence of vaginal breech delivery was 2%. Mothers with weight gain I 5 kg during pregnancy had more normal vaginal deliveries than controls (90% vs. 70%, P < 0.05). Mothers with excessive weight gain during pregnancy had the lowest rate of normal vaginal deliveries (64O), the highest rate of assisted vaginal deliveries (13%) and the highest rate of CS (23%) most of them emergency CS. However, these numbers did not statistically differ from the control group, maybe because of low number of cases. Also, obese mothers with high initial body mass index (BMI) had a high rate of CS (21%) Article
280
Ekblad and Gremnan
Table 3.
Management and outcome of delivery. Weight category I
II
III
IV
V
2 20% over normal weight for height
Weight gain 55 kg
Weight gain 220 kg
Control group
30
56
166
n
71
~20% under normal weight for height 28
Induction of labor (%) Mode of delivery (%) Normal vaginal Forceps or vacuum Breech CS (elective)
36*
25
23
43;
24
78 1 0 7 21% 14
88 0 4 4 8% 4
90* 3 1 3 6% 3
64 13 0 5 23% 18
71 5 2 13 22% 9
300 ~296 17 ?? 15 ll* 6 0
333 f 208 15 zt 18* 13 ?? 13 3
374 zt 208 21 + 25 l3* 11 2
346 f 188 21 f 18 12 ?? 12 0.6
CS (emergency) Labor pattern I stage (min) 311 f 203 II stage @in) 18 f 17 III stage (mitt) 21* 11 Shoulder dystocia (%) 3 Vaginal repair (%) II0 0 1110 0
0 0
4 0
5 0
2 0
Data represent mean f SD, study groups compared with the control group. *P < 0.05; **p < 0.005. CS, cesarean section.
mostly emergency CS during the delivery. Lean women (II), as well as women with weight gain I 5 kg (III), had the lowest rate of CS, 8% and 6%, respectively. The numbers did not reach statistical significance compared with the control group. There were no statistical differences in the length of first and third stage of labor between study and control groups. The second stage of labor was shortest in the group of women with weight gain I 5 kg during pregnancy (P < 0.05). The overall incidence of shoulder dystocia was low: in the control group 0.6%, in the group of lean mothers (II) 0% and in other subgroups 2-3%. There were no statistical differences between the study and control groups. Vaginal lacerations were uncommon in the study group and there were no statistical differences between study and control mothers Int J Gynecol Obstet 39
in the rate of repair of second or third degree lacerations. Neonatal outcome
Table 4 summarizes the overall neonatal outcome in different subgroups. Obese mothers (I) and mothers with excessive weight gain during pregnancy (IV), gave birth to considerably heavier babies than controls (P < 0.05, P < 0.005). The sex ratio was similar in all subgroups (> 50% females) and so, did not have any effect on the birthweight difference between groups. There were more large-for-gestational age babies in the group of obese (I) mothers than in the control group (P < 0.05). Lean mothers (II) delivered smaller babies than controls (P < 0.05) and the number of SGA babies was significantly higher (P < 0.0005) than in the control group. In the
Maternal weight, abnormal weight gain ana’perinatal outcome
Table 4.
281
Neonatal outcome. Weight category I
II
III
IV
V
zr 20% under normal weight to height 28
Weight gain ~5 kg
Weight gain 220 kg
Control group
n
220% over normal weight to height 17
30
56
166
Birthweight (g)
3712 f 614:
3294 zt 362*
3284 f 880
3803 f 538’;
3538 f 535
Weight percentile (%) c2.5 2.5-10 10-50 50-90 90-97.5 >97.5 Apgar score 1’ 5’ 10’ Umbilical vein astrup n PH PC02 PO2
Admitted to NICU n = (%) Hyperbilirubinemia n (%) PNM n (%)
** b
*a
??
0
1 6 35 43 13 2
25 41 17 9
4 18 63 11 4 0
3 14 32 34 14 3
2 42 29 20
8.4 f 1.5 8.8 f 1.1 8.8 f 1.1
8.8 ?? 0.7 9.0 f 0.6 9.0 + 0.6
8.2 z+z1.8 8.5 zt 1.8 8.6 zrz1.8
8.2 f 1.7 8.8 zt 0.6 8.9 zt 0.5
8.6 ?? 0.7 8.9 f 0.6 9.0 f 0.5
29 7.32 f 0.08 5.55 f 1.17 2.98 f 0.81
13 7.31 ?? 0.07 5.78 zt 1.04 2.66 f 0.71
12 7.32 zt 0.09 5.40 zt 1.06 2.93 zt 0.98
27 7.30 ?? 0.10 5.98 f 1.35 2.83 f 0.88
68 7.32 ztz0.0 5.89 zt 10.0 2.91 ZL0.8
2 (3%)
1 (4%)
0
1 (2%)
3 (2%)
12 (18%)
1 (4%)
3 (10%)
3 (5%)
14 (9%)
1 (1%)
0 (0%)
2 (7%)
0 (0%)
2 (1%)
1
I
7
Data represent mean f SD, study groups compared with the controls. NICU, neonatal intensive care unit; PNM, perinatal mortality. *P < 0.005; ***p < 0.0005. *P < 0.05; ?? *asigniflcantly more babies over 90th percentile. ?? **bsigniticantly more babies under 10th percentile.
group of mothers with weight gain less than 5 kg during pregnancy the average birthweight was lower and the percentage of SGA babies was higher than in the control group. *Thedifference was statistically not significant, maybe due to wide standard deviation in the birthweight and small number of SGA babies generally. Neonatal outcome expressed as Apgar scores and umbilical vein blood gas values at birth was equally good in all subgroups. There were no severely asphyxiated babies at birth in this study. The rates of admission to
the neonatal intensive care unit (NICU), of neonatal hyperbilirubinemia and of perinatal mortality did not significantly differ between study and control groups. Discussion Both maternal underweight [2] and obesity [7,10] as well as abnormal weight gain [2] during pregnancy have been reported to increase obstetric risks [15]. In our study the incidence of prepregnancy underweight (BMI 17.2 & 3.4 kg/m2, Article
282
Ekblad and Grenman
~20% under normal weight for height) was 2.4% and that for obesity (BMI 39.5 f 3.4 ks/m*, ~20% above normal weight for height) 6.6%. The incidence of subnormal (s 5 kg) or excessive weight gain (220 kg) during pregnancy was 2.6% and 4.8%, respectively. Similar incidences have been reported from other developed countries [3,12]. In the control group the average prepregnancy weight, BMI and weight gain during pregnancy were 58.3 f 6.5 kg, 22 f 2 kg/m2 and 13 f 3 kg, respectively. In general, obese women gained less weight during pregnancy than did mothers with normal or lean stature. In fact, women with extremely low weight gain during pregnancy (I 5 kg) carried on average 15 kg overweight prior to pregnancy (BMI 26.1 A 6.1 kg/m2), as has been reported also by other groups [3,6]. The highest risk for excessive weight gain (220 kg) during pregnancy was in the group of women with some obesity prior to pregnancy (BMI 23.6 f 4.1 kg/m2). This group of pregnant women identified may need special nutritional counseling during the visits to antenatal care centers. In our study parity did not have any significant effect on weight gain during pregnancy. This is in contrast to earlier studies reporting that high parity goes together with excessive weight gain during pregnancy [6,14]. The discrepancy could be explained by overall low parity in our study. Brown et al. [2] have reported that underweight women have an increased risk for premature deliveries. In this study the percentage of premature deliveries was similar in study and control groups and thus, maternal prepregnancy weight or abnormal weight gain during pregnancy did not affect the gestational length. Our results are in agreement with the data from Frantzen and coworkers [6] and indicate that underweight women have an increased risk of delivering a SGA baby, but not a premature one. In this study, the actual birthweight increased with maternal pregnancy weight gain as also reported from Sweden [13]. Also, exInt J Gynecol Obstet 39
tremely obese women prior to pregnancy had significantly heavier babies than controls, which is in contrast to results of other studies [6,13], where maternal obesity did not increase the actual birthweight. Measuring the symphysis-fundus height is a cost-free and readily available method of estimating fetal size [9]. The usefulness of measuring SF height seems to be independent of maternal prepregnancy weight and weight gain during pregnancy as shown in our study. Short SF height measured at 24 weeks of gestation predicts well an inherited small or intrauterine growth retarded, SGA, baby. In our study, obese women and women with excessive weight gain during pregnancy were more likely to undergo induction of labor than controls. Similar results are reported by other authors [4]. In these weight groups frequent induction of labor may be performed to prevent large-for-date babies. Furthermore, a tendency of increased number of emergency CSs during the labor was seen, if the mother was obese or had excessive weight gain during pregnancy, as suggested also by other authors [4]. In contrast, mothers with weight gain I 5 kg during pregnancy had more spontaneous, normal vaginal deliveries than mothers in the control group. They also had on average smaller babies than controls, which may explain the easier course of delivery. The effect of physical activity during pregnancy was not tested in our study, but it is possible that women with low weight gain during pregnancy were physically more active than mothers in the control group. Good physical condition has been shown to have a positive effect on the course of delivery [5]. A prospective study is needed to evaluate the effect of physical exercise on pregnancy, labor and the newborn in different weight and weight gain subgroups. The rate of CSs is high in most of the developed countries. In our hospital the percentage of CSs during the study was 22% in the control group. Obese women and women with excessive weight gain during pregnancy had a CS rate of 21% and 23%,
Maternal weight, abnormal weight gain and perinatal outcome
respectively. In contrast, underweight women and women with poor weight gain during pregnancy had a CS rate of 8% and 6%. In conclusion, our results indicate that obesity and excessive weight gain during pregnancy carry an increased risk for complications during the delivery. These mothers need special follow-up and counseling during the and delivery. Furthermore, pregnancy underweight women have an increased risk of delivering a SGA baby; they may need prepregnancy nutritional counseling and special follow-up to prevent intrauterine growth retardation. In this study mothers with low weight gain during pregnancy were moderately overweight prior to pregnancy and maybe therefore, low weight gain was not a maternal or neonatal risk factor. Strict recommendations for optimal weight gain during pregnancy seem not to be necessary in developed countries. Neonatal outcome in all weight groups was equally good indicating that the classical risk factors associated with abnormal weight or weight gain prior to and during pregnancy can be controlled with readily available antenatal care and modem obstetric management.
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5
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7
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Address for reprintst
U. Ekblad and Gpeeology DepamntofobstcMcs Turku Univ~ Central Hospital -Ym 4-5 20!52JlTurka, Finlad
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