Inr J Gynecol Ohsret, 1992. 31: 169- 177 International Federation of Gynecology and Obstetrics
Maternal
height and the outcome
J. van Roosmalena
169
of labor in rural Tanzania
and R. Brandb
Departments of “Obstetrics and Gynaecology and hA4edical Stafistics, Leiden State University Hospital. PO Box 9600, 2300 RC Leiden (The Netherlands) (Received December 23rd. 1990) (Revised and accepted June 13th. 1991)
Abstract The influence of maternal height (standardized for parity and birthweight) on obstetrical outcome is studied in 109.5 women giving birth in Lugarawa hospital and 3869 women delivering in Mbozi hospital, both rural hospitals in the South Western Highlands of Tanzania. Short stature wasfound to increase the needfor augmentation of labor in primiparae, the need for operative delivery (cesarean section/symphyseotomy) in all parity groups and the need for vacuum extraction in multiparae. The absence of such an effect of height on perinatal mortality is interpreted as the result of obstetric intervention. It is concluded that maternal height, which is easy to measure, remains a useful tool to predict dtfficult childbirth and cephalopelvic disproportion. Keywords:
Maternal height; Cephalopelvic disproportion; Operative delivery; Perinatal mortality. Introduction
Tallness is generally considered to be advantageous, particularly with regard to childbirth [24]. Although women are genetically shorter than men, they have larger pelvic dimensions [ 131. Stature is found to be significantly related to several pelvic indices, 0020-7292/92/$05.00 @ 1992 International Federation Printed and Published in Ireland
and secular trends in heights of both males and females are accompanied by an increase in pelvic size. This points to environmental factors, one of which is nutrition [2,13,24]. Baird was among the first to correlate the health and physique of women with their reproductive efficiency [24]. Short women have been reported to have higher rates of perinatal mortality, low birthweight and operative delivery [2,8,10,12,24]. In Scotland, Baird found an excess of short women in the lower socio-economic classes (30% as compared to only 7% in the higher classes). He postulated growth stunting as a result of prior childhood malnutrition. In support of this hypothesis, some evidence has been produced by radiological investigations of pelvic anatomy. Flattening of the pelvic brim was much more marked and significantly more frequently seen in short than in tall women, an observation that was also made in males [3]. Thompson 1241 presented evidence that maternal height gradually influenced the outcome of pregnancy in all social classes. There was no tendency, in his material, for the influence of height to be less in some classes than in others. He concluded, that in addition to environmental factors, genetic influences could be involved. A study from Malta in Southern Europe confirmed that the shorter woman continues to carry a higher risk of low birthweight, ceArticle
of Gynecology
and Obstetrics
170
van Roosmalen and Brand
sarean section, low Apgar score, and a bad obstetric history [4]. It is argued that the obstetric significance of a particular height should ,be related to the patient’s own genetic background: hence different cut-off points are to be used for different populations. Recently, a study from the United Kingdom was published, in which the use of maternal height (as an indicator of pelvic size) was combined with the measurement of the symphysis-fundus height (as an indicator of fetal size) [14]. In average sized babies (symphysis-fundus height between the 10th and 90th percentile), increased maternal height was associated with lower operative delivery rates. This association was not present when the fetal size was estimated above the 90th percentile. Fetal size has been shown to increase with height of the mother. It is however only slightly affected by height of the father [5]. Women with obstructed labor will benefit from hospital services which include augmentation with oxytocin and facilities for operative delivery. Pelvic assessment before the onset of labor has not been proven to reliably predict cephalopelvic disproportion [7,16]. When maternal height proves to be a better indicator, screening for cephalopelvic disproportion by the use of height in peripheral antenatal clinics can be useful as a means to reduce maternal and perinatal mortality resulting from obstructed labor. Maternal height will then determine whether a woman should be referred for hospital delivery or not. Therefore, data from two rural hospitals in the South Western Highlands of Tanzania are presented in this article on the relation between maternal height and the outcome of labor, independent of parity of the mother and weight of the newborn. Materials and methods
Out of 1203 women, representing all deliveries from January 1978 to May 1979 in Lugarawa hospital, a rural mission hospital in the South Western Highlands of Tanzania, Int J Gynecol Obsret 37
those with: -
presentations other than vertex, multiple pregnancies, cesarean births for other reasons than cephalopelvic disproportion (CPD), and infants weighing less than 2000 g at birth,
were excluded, leaving 1095 women for analysis. As the aim of this study was to analyze the effect of maternal height on the outcome of pregnancy, it was decided to exclude preterm births. Gestational age, however, was not reliably known and therefore birthweight has been taken as the only available indicator. The weight of 2000 g is approximately equal to the mean birthweight in Lugarawa minus two standard deviations and has been arbitrarily chosen in order to exclude as many preterm births as possible [21]. Maternal height was measured, standing erect, in the antenatal clinic or after delivery by using a measuring rod, hanging on the wall and with 0.5 cm divisions. Women did not wear shoes. A log linear analysis was performed to investigate a possible association of maternal height and the outcome of labor. For this purpose the study group of 1095 women was divided according to: - parity (primiparity, 268 women; parity 1-4, 571 women; parity 5+, 256 women); - birthweight (2000-2999 g, 666 births; 3000+ g, 429 births); - maternal height (below 150 cm, 206 women; 150-159.5 cm, 683 women; 160+ cm, 206 women) (Table 1). The outcome of labor was specified as: - the odds of experiencing perinatal death (24 perinatal deaths); - the odds of needing augmentation of labor with oxytocin (61 augmentations); - the odds of needing operative delivery (50 symphyseotomies and cesarean births for CPD); and - the odds of needing termination of labor with the vacuum extractor (73 vacuum extractions).
Muternul
The need for operative delivery was determined by the hospital’s policy of using the guidelines of the partogram, as has been described elsewhere [ 191. In the log linear analysis, separate models were postulated for the log odds on these four outcomes as a function of birthweight and maternal height. For each outcome variable and for each parity group, two models were considered suitable to investigate the effect of height (adjusted for birthweight and a fortiori, parity): Model 1: the log odds as a function of birthweight only. Model 2: the log odds as a function of birthweight and a linear effect of maternal height. Models 1 and 2 were compared to each other and both to a saturated model (i.e. a model relating the outcome to all birthweight and maternal height categories separately), which by definition has a perfect lit. In testing the goodness of fit of these models the following possible observations could be made with regard to the association of height and the outcome of labor: - a good fit of model 1 and no significantly better Iit of model 2: this substantiates the conclusion that maternal height does not appear to have any influence on the odds. - a good lit of model 2 and a significantly better fit compared to model 1 indicates that the effect of height on the odds is statistically significant and that the effect increases or decreases systematically with height. - a bad fit of both model 1 and 2 (leaving a good fit of the saturated model by definition) indicates that there is an effect of height. This need not be a systematic increase or decrease, however. Only when the effect of height causes a systematic increase or decrease of the odds of the outcome variables, can height be expected to be useful as a screening test. On the basis of this study it would then be possible to draw valid cut-off points, below which the risk of cephalopelvic disproportion is higher.
height
und the outcome
of’ k&w
171
A similar log linear analysis was applied to 3869 women, delivering in Mbozi hospital between June 1980 and May 1983. Mbozi hospital is a rural district hospital in the South Western Highlands of Tanzania. The same criteria for exclusion as in Lugarawa were applied to the 4229 women comprising all births in that period. In Mbozi hospital, maternal height was measured in a different fashion from that practised in Lugarawa. Lines marking 155, 150, 146 and 140 cm, were drawn on the wall in the labor ward. The height of the women was measured by placing a piece of hardboard horizontally on top of the head of the woman. Women stood erect and did not wear shoes. Five categories could be discerned by this method (Table 1): - group 1 (above 155 cm, 1896 women); - group 2 (between 150 and 155 cm, 1286 women); - group 3 (between 146 and 150 cm, 516 women); - group 4 (between 140 and 146 cm, 145 women); - group 5 (below 140 cm, 26 women). Table 1.
Parity. birthweight and maternal
height in the two
study populations.
Lugarawa (‘%I) (N = 1095)
M bozi (‘X) (A’ = 3869)
Primiparity
268 (24.5)
Parity l-4
571 (52.1)
Parity 5+
256 (23.4)
925 (23.9) 2090 (54.0) 854 (22. I)
Birthweight (g) 2000-2999 3000+
666 (60.8) 429 (39.2)
1823 (47. I) 2046 (52.9)
Parity
Maternal height (cm) < 140 140-146 I55 I60+ 206 (18.8)
26 145
( 0.7) ( 3.7)
516 (13.3) 1286 (33.2) 1896 (49. I)
Article
172
van Roosmalen and Brand
- operative delivery (85 symphyseotomies cesarean births); - vacuum extractions (225 extractions).
The Mbozi population was further divided according to: - parity (primiparity, 925 women; parity l-4,2090 women; parity 5+, 854 women); - birthweight (2000-2999 g: 1823 births; 3000+ g, 2046 births). The odds were calculated for the outcome variables: - perinatal deaths (152 cases); - augmentation of labor (147 cases);
Table 2.
Maternal
height.
birthweight
and the outcome
Para 0 (n = 268)
Maternal height (cm)
2000-2999 (n = 189) A. Perinatal death
Maternal
height and the outcome
J. van Roosmalena
169
of labor in rural Tanzania
and R. Brandb
Departments of “Obstetrics and Gynaecology and hA4edical Stafistics, Leiden State University Hospital. PO Box 9600, 2300 RC Leiden (The Netherlands) (Received December 23rd. 1990) (Revised and accepted June 13th. 1991)
Abstract The influence of maternal height (standardized for parity and birthweight) on obstetrical outcome is studied in 109.5 women giving birth in Lugarawa hospital and 3869 women delivering in Mbozi hospital, both rural hospitals in the South Western Highlands of Tanzania. Short stature wasfound to increase the needfor augmentation of labor in primiparae, the need for operative delivery (cesarean section/symphyseotomy) in all parity groups and the need for vacuum extraction in multiparae. The absence of such an effect of height on perinatal mortality is interpreted as the result of obstetric intervention. It is concluded that maternal height, which is easy to measure, remains a useful tool to predict dtfficult childbirth and cephalopelvic disproportion. Keywords:
Maternal height; Cephalopelvic disproportion; Operative delivery; Perinatal mortality. Introduction
Tallness is generally considered to be advantageous, particularly with regard to childbirth [24]. Although women are genetically shorter than men, they have larger pelvic dimensions [ 131. Stature is found to be significantly related to several pelvic indices, 0020-7292/92/$05.00 @ 1992 International Federation Printed and Published in Ireland
and secular trends in heights of both males and females are accompanied by an increase in pelvic size. This points to environmental factors, one of which is nutrition [2,13,24]. Baird was among the first to correlate the health and physique of women with their reproductive efficiency [24]. Short women have been reported to have higher rates of perinatal mortality, low birthweight and operative delivery [2,8,10,12,24]. In Scotland, Baird found an excess of short women in the lower socio-economic classes (30% as compared to only 7% in the higher classes). He postulated growth stunting as a result of prior childhood malnutrition. In support of this hypothesis, some evidence has been produced by radiological investigations of pelvic anatomy. Flattening of the pelvic brim was much more marked and significantly more frequently seen in short than in tall women, an observation that was also made in males [3]. Thompson 1241 presented evidence that maternal height gradually influenced the outcome of pregnancy in all social classes. There was no tendency, in his material, for the influence of height to be less in some classes than in others. He concluded, that in addition to environmental factors, genetic influences could be involved. A study from Malta in Southern Europe confirmed that the shorter woman continues to carry a higher risk of low birthweight, ceArticle
of Gynecology
and Obstetrics
170
van Roosmalen and Brand
sarean section, low Apgar score, and a bad obstetric history [4]. It is argued that the obstetric significance of a particular height should ,be related to the patient’s own genetic background: hence different cut-off points are to be used for different populations. Recently, a study from the United Kingdom was published, in which the use of maternal height (as an indicator of pelvic size) was combined with the measurement of the symphysis-fundus height (as an indicator of fetal size) [14]. In average sized babies (symphysis-fundus height between the 10th and 90th percentile), increased maternal height was associated with lower operative delivery rates. This association was not present when the fetal size was estimated above the 90th percentile. Fetal size has been shown to increase with height of the mother. It is however only slightly affected by height of the father [5]. Women with obstructed labor will benefit from hospital services which include augmentation with oxytocin and facilities for operative delivery. Pelvic assessment before the onset of labor has not been proven to reliably predict cephalopelvic disproportion [7,16]. When maternal height proves to be a better indicator, screening for cephalopelvic disproportion by the use of height in peripheral antenatal clinics can be useful as a means to reduce maternal and perinatal mortality resulting from obstructed labor. Maternal height will then determine whether a woman should be referred for hospital delivery or not. Therefore, data from two rural hospitals in the South Western Highlands of Tanzania are presented in this article on the relation between maternal height and the outcome of labor, independent of parity of the mother and weight of the newborn. Materials and methods
Out of 1203 women, representing all deliveries from January 1978 to May 1979 in Lugarawa hospital, a rural mission hospital in the South Western Highlands of Tanzania, Int J Gynecol Obsret 37
those with: -
presentations other than vertex, multiple pregnancies, cesarean births for other reasons than cephalopelvic disproportion (CPD), and infants weighing less than 2000 g at birth,
were excluded, leaving 1095 women for analysis. As the aim of this study was to analyze the effect of maternal height on the outcome of pregnancy, it was decided to exclude preterm births. Gestational age, however, was not reliably known and therefore birthweight has been taken as the only available indicator. The weight of 2000 g is approximately equal to the mean birthweight in Lugarawa minus two standard deviations and has been arbitrarily chosen in order to exclude as many preterm births as possible [21]. Maternal height was measured, standing erect, in the antenatal clinic or after delivery by using a measuring rod, hanging on the wall and with 0.5 cm divisions. Women did not wear shoes. A log linear analysis was performed to investigate a possible association of maternal height and the outcome of labor. For this purpose the study group of 1095 women was divided according to: - parity (primiparity, 268 women; parity 1-4, 571 women; parity 5+, 256 women); - birthweight (2000-2999 g, 666 births; 3000+ g, 429 births); - maternal height (below 150 cm, 206 women; 150-159.5 cm, 683 women; 160+ cm, 206 women) (Table 1). The outcome of labor was specified as: - the odds of experiencing perinatal death (24 perinatal deaths); - the odds of needing augmentation of labor with oxytocin (61 augmentations); - the odds of needing operative delivery (50 symphyseotomies and cesarean births for CPD); and - the odds of needing termination of labor with the vacuum extractor (73 vacuum extractions).
Muternul
The need for operative delivery was determined by the hospital’s policy of using the guidelines of the partogram, as has been described elsewhere [ 191. In the log linear analysis, separate models were postulated for the log odds on these four outcomes as a function of birthweight and maternal height. For each outcome variable and for each parity group, two models were considered suitable to investigate the effect of height (adjusted for birthweight and a fortiori, parity): Model 1: the log odds as a function of birthweight only. Model 2: the log odds as a function of birthweight and a linear effect of maternal height. Models 1 and 2 were compared to each other and both to a saturated model (i.e. a model relating the outcome to all birthweight and maternal height categories separately), which by definition has a perfect lit. In testing the goodness of fit of these models the following possible observations could be made with regard to the association of height and the outcome of labor: - a good fit of model 1 and no significantly better Iit of model 2: this substantiates the conclusion that maternal height does not appear to have any influence on the odds. - a good lit of model 2 and a significantly better fit compared to model 1 indicates that the effect of height on the odds is statistically significant and that the effect increases or decreases systematically with height. - a bad fit of both model 1 and 2 (leaving a good fit of the saturated model by definition) indicates that there is an effect of height. This need not be a systematic increase or decrease, however. Only when the effect of height causes a systematic increase or decrease of the odds of the outcome variables, can height be expected to be useful as a screening test. On the basis of this study it would then be possible to draw valid cut-off points, below which the risk of cephalopelvic disproportion is higher.
height
und the outcome
of’ k&w
171
A similar log linear analysis was applied to 3869 women, delivering in Mbozi hospital between June 1980 and May 1983. Mbozi hospital is a rural district hospital in the South Western Highlands of Tanzania. The same criteria for exclusion as in Lugarawa were applied to the 4229 women comprising all births in that period. In Mbozi hospital, maternal height was measured in a different fashion from that practised in Lugarawa. Lines marking 155, 150, 146 and 140 cm, were drawn on the wall in the labor ward. The height of the women was measured by placing a piece of hardboard horizontally on top of the head of the woman. Women stood erect and did not wear shoes. Five categories could be discerned by this method (Table 1): - group 1 (above 155 cm, 1896 women); - group 2 (between 150 and 155 cm, 1286 women); - group 3 (between 146 and 150 cm, 516 women); - group 4 (between 140 and 146 cm, 145 women); - group 5 (below 140 cm, 26 women). Table 1.
Parity. birthweight and maternal
height in the two
study populations.
Lugarawa (‘%I) (N = 1095)
M bozi (‘X) (A’ = 3869)
Primiparity
268 (24.5)
Parity l-4
571 (52.1)
Parity 5+
256 (23.4)
925 (23.9) 2090 (54.0) 854 (22. I)
Birthweight (g) 2000-2999 3000+
666 (60.8) 429 (39.2)
1823 (47. I) 2046 (52.9)
Parity
Maternal height (cm) < 140 140-146 I55 I60+ 206 (18.8)
26 145
( 0.7) ( 3.7)
516 (13.3) 1286 (33.2) 1896 (49. I)
Article
172
van Roosmalen and Brand
- operative delivery (85 symphyseotomies cesarean births); - vacuum extractions (225 extractions).
The Mbozi population was further divided according to: - parity (primiparity, 925 women; parity l-4,2090 women; parity 5+, 854 women); - birthweight (2000-2999 g: 1823 births; 3000+ g, 2046 births). The odds were calculated for the outcome variables: - perinatal deaths (152 cases); - augmentation of labor (147 cases);
Table 2.
Maternal
height.
birthweight
and the outcome
Para 0 (n = 268)
Maternal height (cm)
2000-2999 (n = 189) A. Perinatal death
