AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
January 7997
EFFECTS OF GESTATIONAL WEIGHT GAIN IN MORBIDLY OBESE WOMEN: I. MATERNAL MORBIDITY Robert E. Ratner, M.D., Lewis H. Hamner, HI, M.D., and Nelson B. Isada, M.D.
ABSTRACT
Obesity is a common clinical problem in the United States and carries with it a marked increase in morbidity and mortality.l When pregnancy is superimposed on this obese state, mothers are exposed to even greater risks than those seen in the nonobese gravid individual.23 In the nonobese individual, an optimum fetal outcome is achieved as the mother approaches 120% of ideal body weight (IBW) at delivery.4 Although this is appropriate for women of normal or less than normal weight preconceptionally, no comparable data exist for the morbidly obese woman. Some authors have suggested limiting weight gain in the obese patient in an attempt to decrease complications of pregnancy.56 In moderately obese women (greater than 135% IBW) limited gestational weight gain of 16 pounds was associated with improved perinatal outcome.7 This recommendation, however, remains controversial, with other investigators recommending a 20 to 27 pound gestational weight gain regardless of preconception weight.8-9 The clinical observation that obese, pregnant women frequently fail to gain as much weight as their
Downloaded by: National University of Singapore. Copyrighted material.
Current recommendations for appropriate weight gain in pregnancy suggest an optimum of 120% of ideal body weight (IBW) at delivery. This represents an increase of approximately 24 pounds in the normal weight woman and even the obese patient (more than 135% IBW) is told to gain 16 pounds. Information concerning gestational weight gain in the morbidly obese woman (more than 160% IBW) has not been reported. We evaluated 40 morbidly obese pregnant women for maternal morbidity relative to gestational weight gain. No correlation was found between maternal weight gain and the development of gestational diabetes, pregnancy-induced hypertension, preeclampsia, preterm labor, premature rupture of membranes, incompetent cervix, or intrauterine growth retardation. The incidence of primary cesarean delivery was statistically greater in those women gaining more than 24 pounds (p < 0.05). It appears that current recommendations for gestational weight gain in the morbidly obese are excessive and may result in increased maternal risk.
nonobese counterparts allows us to utilize a casecontrolled study analyzing morbidly obese patients to assess maternal complications related to maternal weight gain.10 The purpose of this study is to examine the incidence of maternal complications relative to maternal weight gain in an effort to recommend dietary intervention in morbidly obese pregnant women. METHODS AND MATERIALS
Between 1982 and 1986, 40 pregnant women followed at the George Washington University Medical Center High Risk Obstetrical Clinic were classified as morbidly obese. Preconceptionally, these women exceeded 160% IBW as determined by Metropolitan Life Insurance actuarial tables for desirable weights by height and frame.11 All women had received traditional dietary counselling to maintain a 30 to 35 Kcal/kg IBW diet throughout their pregnancy. Women were seen on an every other week
Division of Endocrinology, Department of Medicine and Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, George Washington University Medical Center, Washington, DC Presented in part at the Society of Perinatal Obstetricians, February, 1987, Orlando, Florida Reprint Requests: Dr. Ratner, Division of Endocrinology, George Washington University Medical Center, 2150 Pennsylvania Ave., N.W., Washington, DC, 20037 Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
21
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
RESULTS
Mean age for the population was 29.7 years with a mean gestational age at the time of delivery of 38.1 weeks. Our patient population had a mean parity of 3.2 for the pregnancy studied. Preconception body weights ranged from 160 to 410 pounds, with a mean weight of 246 pounds, or 199.9% of ideal. Mean gestational weight gain for the group was 21.3 pounds, with a range of 18 pound weight loss to a 64 pound weight gain. Not surprisingly, our morbidly obese population had an extremely high incidence of preexisting medical complications (Table 1). Thirty-five percent of the patients suffered from pregestational hypertension, and 10% were found to have pregestational diabetes mellitus. In those without antecedent disease, an additional 19.2% developed pregnancy-induced hypertension and 25% developed gestational diabetes mellitus compared with a 4% prevalence of gestational diabetes in our general obstetric population. Table 2 summarizes demographics and preexisting disease processes in groups broken down in this fashion. There was no statistical difference in age, parity, gestational age at delivery, or percent 22 IB W prior to conception in any of the groups. There
Table 1.
Summary of Medical Complications in Patients Prevalence (%)
Hypertension Pregnancy-induced hypertension Preeclampsia/eclampsia Diabetes Gestational diabetes Intrauterine growth retardation Premature rupture of membranes Preterm labor Incompetent cervix Ketonuria History of smoking Primary cesarean section
35.0 19.2 5.0
10.0 25.0 0.0 7.5 0.0 7.5
15.0 17.5 39.3
was no difference in the prevalence of smoking or hypertension in any of the groups. As expected, differences in weight gain between groups were significant with a p < 0.0001. The prevalence of preexisting diabetes mellitus was significantly greater (p < 0.02) in those individuals who ultimately gained greater than 24 pounds during their pregnancy. Complications of pregnancy are outlined in Table 3, with subjects again divided according to gestational weight gain criteria. In those individuals without antecedent diabetes mellitus or hypertension, the greater weight gains appeared to result in a somewhat higher incidence of gestational diabetes and pregnancy-induced hypertension. Women gaining greater than 10 pounds during pregnancy had a 29.6% incidence of gestational diabetes and a 21.1% incidence of pregnancy-induced hypertension compared with 11.1% and 14.3% in those gaining less than 10 pounds. This same trend was seen if a gestational weight gain of 16 pounds is used as the cutoff in which those gaining more weight demonstrated a 30.4% incidence of gestational diabetes and a 25% incidence of pregnancy-induced hypertension compared with 15.3% and 10%, respectively, in those gaining less than 16 pounds. Despite statistically significant differences in weight gain, there was no difference in the frequency of ketonuria among the groups. In addition, intrauterine growth retardation was not found in any of our study patients, suggesting adequate placental delivery of nutrients independent of maternal weight gain. There were no differences among any of the groups regarding the incidence of cervical incompetence, preterm labor, or premature rupture of membranes. Twelve of our study patients were offered a trial of labor, but chose to have an elective repeat cesarean delivery. Of the remaining 28 pregnancies, 11 (39%) required primary cesarean section delivery for soft tissue dystocia, cephalopelvic disproportion, or failure to progress. Those women gaining greater than 24 pounds required primary cesarean section 58.3% of the time compared with 25% in those gaining less than 24 pounds (p < 0.0005). This difference was not statistically significant in those gaining less than
Downloaded by: National University of Singapore. Copyrighted material.
basis from presentation of pregnancy until 30 weeks gestation, at which point they were seen on a weekly basis. At each visit, weight, blood pressure, and urine ketone testing were routinely performed. All women underwent a 50 gm glucose challenge test between weeks 24 and 28 of their pregnancy to screen for the presence of gestational diabetes. If the 1 hour plasma glucose exceeded 135 mg/dl, the individuals underwent the standard 3 hour, 100 gm glucose tolerance test with diagnosis of diabetes being established by O'Sullivan criteria. History of chronic diseases, including hypertension and diabetes, were sought, as was a history of confounding variables such as drug treatment or smoking history. Patients were then evaluated for complications of pregnancy, including the presence of pregnancy-induced hypertension, gestational diabetes, preeclampsia/eclampsia, preterm rupture of membranes, preterm labor, incompetent cervix, and their ultimate route of delivery. Patients were stratified according to weight gain throughout pregnancy. Comparisons were made between those individuals with gestational weight gains of less than or greater than 24 pounds as recommended by the American College of Obstetricians and Gynecologists (ACOG),15 gestational weight gains of less than or greater than 16 pounds as suggested by Naeye,7 and those with gestational weight gains of less than or greater than 10 pounds. Statistical analyses were performed using the Statistical Analysis System (SAS) computer program utilizing chi-square and Fisher exact determinations where appropriate.
January 1991
MATERNAL MORBIDITY IN OBESE PREGNANCIES/Ratner, Hamner, Isada Table 2. Summary of Population by Weight Gain (lbs) 10
(n = 10)
(n = 30)
P
0.001
6.8
31.6
26.9 29.0
3.1
3.2
39.0 199.6 10.0 30.0 20.0
37.8 200.0 10.0 40.0 16.0
NS* NS NS NS NS NS NS
Weight gain (Ib) Age (yr) Parity Gestational age (wk) IBW* (%) Diabetes mellitus (%) Hypertension (%) SMOK* (%)
4.6
76
24
(n = 14)
(n = 26)
P
(n = 21)
(n = 19)
P
0.001
10.8 31.7
32.9 27.4
0.001
31.2
29.1 28.8
3.5
2.9
3.4
2.8
38.6 201.0
37.8 199.0 11.5 42.3 15.3
38.6 197.0
37.4 202.0 15.7 36.8 21.0
7.1
28.5 21.4
NS NS NS NS NS NS NS
4.7
38.0 14.2
NS NS NS NS 0.2 NS NS
"NS: Not significant; IBW: ideal body weight; SMOK: smoking during pregnancy.
Incidence of Pregnancy Complications (%) by Weight Gain (lbs)
Condition Gestational diabetes Pregnancy-induced hypertension Preeclampsia/eclampsia Intrauterine growth retardation Preterm labor Premature rupture of membranes Ketonuria Incompetent cervix
10
/6
24
(n = 10)
(n = 30)
P
(n = 14)
(n = 26)
P
(n = 21)
(n = 19)
P
11. 1 14. 3 0 0 0 0 10. 0 0
29.6 21.1
NS NS NS NS NS NS NS NS
15.3 10.0
30.4 25.0
NS
30.0 15.3
0 0 0 7.1 7.1 0
7.6 0 0 7.7
18.8 23.1 10.5
NS NS NS NS NS NS NS NS
6.0 0 0
10.0 16.6 0
19.2 7.6
NS NS NS NS NS NS NS
0 0 0 4.7
0 0
19.0
10.5 10.5
4.7
5.2
NS: Not significant.
10 pounds or 16 pounds versus greater than 10 pounds or 16 pounds, respectively (Table 4). DISCUSSION
The health consequences of obesity in the general population have been well explored1 and unequivocally demonstrate a two- to fourfold increase in mortality. Endocrine, pulmonary, cardiovascular, and orthopedic complications are well described in the nonpregnant obese population. Obstetric risks are also markedly increased in the presence of maternal obesity. Medical complications, including hypertension, hyperglycemia, thrombophlebitis, and anesthesia and operative risks are greater in the obese pregnant patient compared with the lean.3 There has also been some suggestion that additional gestational weight gain superimposed on preexisting maternal obesity further increases these risks.12 Specific obstetric complications have also been described in the obese mother. These include the development of toxemia of pregnancy,13 cephalopelvic disproportion, and the need for primary cesarean section delivery.14 Our data confirm the
markedly increased incidence of preexisting chronic hypertension and diabetes mellitus in obese pregnant women in comparison to their lean counterparts, as well as the increased need for cesarean delivery. Nutritional recommendations for obese women in pregnancy vary throughout the literature. Current ACOG recommendations emphasize the same principles of prenatal nutrition in obese women as those that apply to normal weight women. Furthermore, weight reduction regimens are recommended only following delivery.15 One of the difficulties in analyzing outcomes of pregnancy in obese individuals is the varying definition of obesity. Previous studies have defined obesity as greater than 120% IBW9 or greater than 135% IBW7 prior to conception. Even so, analysis of fetal outcome in these studies resulted in recommendations of maternal weight gain of 25 pounds and 16 pounds, respectively. All agree, however, that if a program of weight reduction utilizing a diet restricted in calories is recommended for obese pregnant women, it must include all essential nutrients and must be monitored closely to ensure that ketosis does not develop. In our noninterventional study, fully 33% of our study
Primary Cesarean Section Deliveries (o/ \ by Weight Gam < 16
January 7997
EFFECTS OF GESTATIONAL WEIGHT GAIN IN MORBIDLY OBESE WOMEN: I. MATERNAL MORBIDITY Robert E. Ratner, M.D., Lewis H. Hamner, HI, M.D., and Nelson B. Isada, M.D.
ABSTRACT
Obesity is a common clinical problem in the United States and carries with it a marked increase in morbidity and mortality.l When pregnancy is superimposed on this obese state, mothers are exposed to even greater risks than those seen in the nonobese gravid individual.23 In the nonobese individual, an optimum fetal outcome is achieved as the mother approaches 120% of ideal body weight (IBW) at delivery.4 Although this is appropriate for women of normal or less than normal weight preconceptionally, no comparable data exist for the morbidly obese woman. Some authors have suggested limiting weight gain in the obese patient in an attempt to decrease complications of pregnancy.56 In moderately obese women (greater than 135% IBW) limited gestational weight gain of 16 pounds was associated with improved perinatal outcome.7 This recommendation, however, remains controversial, with other investigators recommending a 20 to 27 pound gestational weight gain regardless of preconception weight.8-9 The clinical observation that obese, pregnant women frequently fail to gain as much weight as their
Downloaded by: National University of Singapore. Copyrighted material.
Current recommendations for appropriate weight gain in pregnancy suggest an optimum of 120% of ideal body weight (IBW) at delivery. This represents an increase of approximately 24 pounds in the normal weight woman and even the obese patient (more than 135% IBW) is told to gain 16 pounds. Information concerning gestational weight gain in the morbidly obese woman (more than 160% IBW) has not been reported. We evaluated 40 morbidly obese pregnant women for maternal morbidity relative to gestational weight gain. No correlation was found between maternal weight gain and the development of gestational diabetes, pregnancy-induced hypertension, preeclampsia, preterm labor, premature rupture of membranes, incompetent cervix, or intrauterine growth retardation. The incidence of primary cesarean delivery was statistically greater in those women gaining more than 24 pounds (p < 0.05). It appears that current recommendations for gestational weight gain in the morbidly obese are excessive and may result in increased maternal risk.
nonobese counterparts allows us to utilize a casecontrolled study analyzing morbidly obese patients to assess maternal complications related to maternal weight gain.10 The purpose of this study is to examine the incidence of maternal complications relative to maternal weight gain in an effort to recommend dietary intervention in morbidly obese pregnant women. METHODS AND MATERIALS
Between 1982 and 1986, 40 pregnant women followed at the George Washington University Medical Center High Risk Obstetrical Clinic were classified as morbidly obese. Preconceptionally, these women exceeded 160% IBW as determined by Metropolitan Life Insurance actuarial tables for desirable weights by height and frame.11 All women had received traditional dietary counselling to maintain a 30 to 35 Kcal/kg IBW diet throughout their pregnancy. Women were seen on an every other week
Division of Endocrinology, Department of Medicine and Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, George Washington University Medical Center, Washington, DC Presented in part at the Society of Perinatal Obstetricians, February, 1987, Orlando, Florida Reprint Requests: Dr. Ratner, Division of Endocrinology, George Washington University Medical Center, 2150 Pennsylvania Ave., N.W., Washington, DC, 20037 Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
21
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
RESULTS
Mean age for the population was 29.7 years with a mean gestational age at the time of delivery of 38.1 weeks. Our patient population had a mean parity of 3.2 for the pregnancy studied. Preconception body weights ranged from 160 to 410 pounds, with a mean weight of 246 pounds, or 199.9% of ideal. Mean gestational weight gain for the group was 21.3 pounds, with a range of 18 pound weight loss to a 64 pound weight gain. Not surprisingly, our morbidly obese population had an extremely high incidence of preexisting medical complications (Table 1). Thirty-five percent of the patients suffered from pregestational hypertension, and 10% were found to have pregestational diabetes mellitus. In those without antecedent disease, an additional 19.2% developed pregnancy-induced hypertension and 25% developed gestational diabetes mellitus compared with a 4% prevalence of gestational diabetes in our general obstetric population. Table 2 summarizes demographics and preexisting disease processes in groups broken down in this fashion. There was no statistical difference in age, parity, gestational age at delivery, or percent 22 IB W prior to conception in any of the groups. There
Table 1.
Summary of Medical Complications in Patients Prevalence (%)
Hypertension Pregnancy-induced hypertension Preeclampsia/eclampsia Diabetes Gestational diabetes Intrauterine growth retardation Premature rupture of membranes Preterm labor Incompetent cervix Ketonuria History of smoking Primary cesarean section
35.0 19.2 5.0
10.0 25.0 0.0 7.5 0.0 7.5
15.0 17.5 39.3
was no difference in the prevalence of smoking or hypertension in any of the groups. As expected, differences in weight gain between groups were significant with a p < 0.0001. The prevalence of preexisting diabetes mellitus was significantly greater (p < 0.02) in those individuals who ultimately gained greater than 24 pounds during their pregnancy. Complications of pregnancy are outlined in Table 3, with subjects again divided according to gestational weight gain criteria. In those individuals without antecedent diabetes mellitus or hypertension, the greater weight gains appeared to result in a somewhat higher incidence of gestational diabetes and pregnancy-induced hypertension. Women gaining greater than 10 pounds during pregnancy had a 29.6% incidence of gestational diabetes and a 21.1% incidence of pregnancy-induced hypertension compared with 11.1% and 14.3% in those gaining less than 10 pounds. This same trend was seen if a gestational weight gain of 16 pounds is used as the cutoff in which those gaining more weight demonstrated a 30.4% incidence of gestational diabetes and a 25% incidence of pregnancy-induced hypertension compared with 15.3% and 10%, respectively, in those gaining less than 16 pounds. Despite statistically significant differences in weight gain, there was no difference in the frequency of ketonuria among the groups. In addition, intrauterine growth retardation was not found in any of our study patients, suggesting adequate placental delivery of nutrients independent of maternal weight gain. There were no differences among any of the groups regarding the incidence of cervical incompetence, preterm labor, or premature rupture of membranes. Twelve of our study patients were offered a trial of labor, but chose to have an elective repeat cesarean delivery. Of the remaining 28 pregnancies, 11 (39%) required primary cesarean section delivery for soft tissue dystocia, cephalopelvic disproportion, or failure to progress. Those women gaining greater than 24 pounds required primary cesarean section 58.3% of the time compared with 25% in those gaining less than 24 pounds (p < 0.0005). This difference was not statistically significant in those gaining less than
Downloaded by: National University of Singapore. Copyrighted material.
basis from presentation of pregnancy until 30 weeks gestation, at which point they were seen on a weekly basis. At each visit, weight, blood pressure, and urine ketone testing were routinely performed. All women underwent a 50 gm glucose challenge test between weeks 24 and 28 of their pregnancy to screen for the presence of gestational diabetes. If the 1 hour plasma glucose exceeded 135 mg/dl, the individuals underwent the standard 3 hour, 100 gm glucose tolerance test with diagnosis of diabetes being established by O'Sullivan criteria. History of chronic diseases, including hypertension and diabetes, were sought, as was a history of confounding variables such as drug treatment or smoking history. Patients were then evaluated for complications of pregnancy, including the presence of pregnancy-induced hypertension, gestational diabetes, preeclampsia/eclampsia, preterm rupture of membranes, preterm labor, incompetent cervix, and their ultimate route of delivery. Patients were stratified according to weight gain throughout pregnancy. Comparisons were made between those individuals with gestational weight gains of less than or greater than 24 pounds as recommended by the American College of Obstetricians and Gynecologists (ACOG),15 gestational weight gains of less than or greater than 16 pounds as suggested by Naeye,7 and those with gestational weight gains of less than or greater than 10 pounds. Statistical analyses were performed using the Statistical Analysis System (SAS) computer program utilizing chi-square and Fisher exact determinations where appropriate.
January 1991
MATERNAL MORBIDITY IN OBESE PREGNANCIES/Ratner, Hamner, Isada Table 2. Summary of Population by Weight Gain (lbs) 10
(n = 10)
(n = 30)
P
0.001
6.8
31.6
26.9 29.0
3.1
3.2
39.0 199.6 10.0 30.0 20.0
37.8 200.0 10.0 40.0 16.0
NS* NS NS NS NS NS NS
Weight gain (Ib) Age (yr) Parity Gestational age (wk) IBW* (%) Diabetes mellitus (%) Hypertension (%) SMOK* (%)
4.6
76
24
(n = 14)
(n = 26)
P
(n = 21)
(n = 19)
P
0.001
10.8 31.7
32.9 27.4
0.001
31.2
29.1 28.8
3.5
2.9
3.4
2.8
38.6 201.0
37.8 199.0 11.5 42.3 15.3
38.6 197.0
37.4 202.0 15.7 36.8 21.0
7.1
28.5 21.4
NS NS NS NS NS NS NS
4.7
38.0 14.2
NS NS NS NS 0.2 NS NS
"NS: Not significant; IBW: ideal body weight; SMOK: smoking during pregnancy.
Incidence of Pregnancy Complications (%) by Weight Gain (lbs)
Condition Gestational diabetes Pregnancy-induced hypertension Preeclampsia/eclampsia Intrauterine growth retardation Preterm labor Premature rupture of membranes Ketonuria Incompetent cervix
10
/6
24
(n = 10)
(n = 30)
P
(n = 14)
(n = 26)
P
(n = 21)
(n = 19)
P
11. 1 14. 3 0 0 0 0 10. 0 0
29.6 21.1
NS NS NS NS NS NS NS NS
15.3 10.0
30.4 25.0
NS
30.0 15.3
0 0 0 7.1 7.1 0
7.6 0 0 7.7
18.8 23.1 10.5
NS NS NS NS NS NS NS NS
6.0 0 0
10.0 16.6 0
19.2 7.6
NS NS NS NS NS NS NS
0 0 0 4.7
0 0
19.0
10.5 10.5
4.7
5.2
NS: Not significant.
10 pounds or 16 pounds versus greater than 10 pounds or 16 pounds, respectively (Table 4). DISCUSSION
The health consequences of obesity in the general population have been well explored1 and unequivocally demonstrate a two- to fourfold increase in mortality. Endocrine, pulmonary, cardiovascular, and orthopedic complications are well described in the nonpregnant obese population. Obstetric risks are also markedly increased in the presence of maternal obesity. Medical complications, including hypertension, hyperglycemia, thrombophlebitis, and anesthesia and operative risks are greater in the obese pregnant patient compared with the lean.3 There has also been some suggestion that additional gestational weight gain superimposed on preexisting maternal obesity further increases these risks.12 Specific obstetric complications have also been described in the obese mother. These include the development of toxemia of pregnancy,13 cephalopelvic disproportion, and the need for primary cesarean section delivery.14 Our data confirm the
markedly increased incidence of preexisting chronic hypertension and diabetes mellitus in obese pregnant women in comparison to their lean counterparts, as well as the increased need for cesarean delivery. Nutritional recommendations for obese women in pregnancy vary throughout the literature. Current ACOG recommendations emphasize the same principles of prenatal nutrition in obese women as those that apply to normal weight women. Furthermore, weight reduction regimens are recommended only following delivery.15 One of the difficulties in analyzing outcomes of pregnancy in obese individuals is the varying definition of obesity. Previous studies have defined obesity as greater than 120% IBW9 or greater than 135% IBW7 prior to conception. Even so, analysis of fetal outcome in these studies resulted in recommendations of maternal weight gain of 25 pounds and 16 pounds, respectively. All agree, however, that if a program of weight reduction utilizing a diet restricted in calories is recommended for obese pregnant women, it must include all essential nutrients and must be monitored closely to ensure that ketosis does not develop. In our noninterventional study, fully 33% of our study
Primary Cesarean Section Deliveries (o/ \ by Weight Gam < 16
