Journal of Obesity and Metabolic Research

: 2014  |  Volume : 1  |  Issue : 3  |  Page : 143--148

Association between high maternal body mass index and feto-maternal outcome

Prabha Kumari, Mamta Gupta, Prabhneet Kahlon, Shalini Malviya 
 Department of Obstetrics and Gynaecology, NDMC Medical College and Hindu Rao Hospital, Malkaganj, New Delhi, India

Correspondence Address:
Prabha Kumari
Doctor«SQ»s Flat No. 21, Hindu Rao Hospital Campus, Malkaganj, New Delhi 110 007


Aim: The aim was to examine the association between high maternal body mass index (BMI) and feto-maternal outcome in primigravida women. Settings and Design: Observational case-control study. Subjects and Methods: A case-control study was conducted on pregnant women admitted for delivery in the labor ward having height and weight recorded before pregnancy or up to 12 weeks of pregnancy fulfilling inclusion criteria. The control group of 200 women with BMI in the normal range (20-24.9 Kg/m 2 ) was compared with study group of 200 women with BMI 25-29.9 Kg/m 2 and more than 30 Kg/m 2 . Outcome measures were maternal complications, obstetric complications and neonatal complications. Statistical Analysis Used: Data were entered and analyzed using IBM SPSS Statistics 21. The strength of association expressed as the odd ratio with 95% confidential interval values. Results: We found a linear relationship between increasing BMI and the risk of developing preeclampsia, gestational diabetes mellitus, failed induction of labor, cesarean section, both elective and emergency, postpartum hemorrhage, abnormal birth weight and neonatal intensive care unit admission. Conclusions: Obese pregnant women are at a higher risk of feto-maternal complications. Since it is a modifiable and preventable condition, preconception counselling, treatment of obesity before conception and awareness regarding associated health risks are highly desirable.

How to cite this article:
Kumari P, Gupta M, Kahlon P, Malviya S. Association between high maternal body mass index and feto-maternal outcome.J Obes Metab Res 2014;1:143-148

How to cite this URL:
Kumari P, Gupta M, Kahlon P, Malviya S. Association between high maternal body mass index and feto-maternal outcome. J Obes Metab Res [serial online] 2014 [cited 2020 Jul 3 ];1:143-148
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Maternal obesity has emerged as a major public health problem in developed, as well as developing countries. [1] As a result, many pregnant women are seen with higher body mass index (BMI). An increased association of morbidity and mortality with obesity is well established in both pregnant and nonpregnant women. [2],[3],[4],[5] Pregnancy with obesity is considered as high risk, and it causes substantial feto-maternal morbidity and mortality. Hence the objective of this study was to examine the association between high BMI and feto-maternal outcome in primigravida women delivering singleton babies.


This observational case-control study was conducted over a period of 1 year. Total number of deliveries was 6020 in our institution during this period of study. Cases and controls were selected from the pregnant women admitted for delivery in the labor ward having height and weight recorded before pregnancy or up to 12 weeks of pregnancy.

Inclusion criteria were age between 20 and 35 years, primigravida with a singleton pregnancy in cephalic presentation having hemoglobin concentration more than 9 g%.

Exclusion criteria were multigravida, with malpresentation, late booking, having babies with any congenital abnormalities, placenta previa and women with medical disorders such as diabetes mellitus, chronic hypertension, cardiac or endocrine disorders, hemoglobin concentration <9 g% and surgical conditions. This allowed reduction of confounding factors to a minimum.

All selected subjects were informed and consent was taken for participation in the study. Detailed history was taken and complete examination was done. Specific investigations for patients having different variables were undertaken.

Socio-demographic variables extracted included age at delivery, height and weight measured and recorded before or at first antenatal visit before 12 weeks of pregnancy, booking or first antenatal visit and socioeconomic status as per modified Kuppuswamy classification. [6] BMI was calculated using the formula weight (kg)/height (m 2 ). The women were then categorized into three groups according to their BMI as follows as per CDC criteria. [7]

Normal: BMI of 20-24.9 Kg/m 2 (n = 200)

Overweight: BMI of 25-29.9 Kg/m 2 (n = 168)

Obese: BMI of more than 30 Kg/m 2 (n = 32)

The group of 200 women with BMI in the normal range (20-24.9 Kg/m 2 ) was used as a control group and a group of 200 women with BMI 25-29.9 Kg/m 2 and more than 30 Kg/m 2 were selected as study cases for the analysis.

Outcome measures were maternal complications such as preeclampsia, gestational diabetes mellitus (GDM), postpartum hemorrhage (PPH), and postoperative wound infection; obstetric complications such as induction of labor (IOL), failed IOL, instrumental delivery, elective and emergency caesarean sections; neonatal complications such as preterm birth, post-term pregnancy (defined as a pregnancy over 41 weeks of gestation), low-birth weight (LBW) defined as birth weight < 2500g, macrosomia (defined as birth weight of more than 4000 g), intrauterine death (IUD), low Apgar score < 7 at 1 min and neonatal intensive care unit (NICU) admission. A blood loss of more than 500mL in vaginal delivery and more than 1000mL in caesarean delivery was considered to be excessive as per the definition of PPH by the World Health Organization. [8] We used graduated under-buttock drapes for vaginal birth and suction bottles for cesarean birth to collect blood and weighed all blood soaked materials to determine cumulative volume of post blood loss.

Gestational age was recorded according to the last menstrual period and was confirmed by ultrasound. In case of discrepancy, the early pregnancy ultrasound date was taken as the actual gestational age.

Data were entered and analyzed using IBM SPSS Statistics 21(IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp). Mean with a standard deviation were calculated for numerical variables and proportions for categorical variables. Significance of difference was calculated using t-test, Chi-square test and Fisher exact test where applicable. The strength of association had been expressed as the odd ratio of obese versus control along with 95% confidential interval values.


A total of 400 women having a singleton pregnancy were included in the study. 200 women with normal BMI (20-24.9 kg/m 2 ) were taken as controls and 200 women with high BMI (>25.0 kg/m 2 ) were taken as cases. Of these 200 cases of high BMI, 168 (84%) were overweight (BMI- 25-29.9) and 32 (16%) were obese (BMI > 30).

A comparison of the socio-demographic characteristics of the women in the three BMI groups is presented in [Table 1]. The mean age at delivery (in years) were 23.13 ± 1.91, 23.90 ± 3.26, and 24.81 ± 3.03 in normal, overweight and obese BMI groups respectively. Mean BMI (in Kg/m 2 ) were 21.16 ± 1.7, 27.49 ± 1.36, and 31.02 ± 0.93 in respective groups. Available pre-pregnancy weight in three groups were restricted to 49 (24.5%), 58 (34.52%) and 21 (65.62%) women, respectively; rest of the women from the groups (151, 75.5%; 110, 65.48% and 11, 34.38%) had first visits at the antenatal clinic of up to 12 weeks of gestation-we checked their weight recordings at the time of booking, which were not different from weights of women in the respective BMI categories. The women of our study population were from either lower, lower middle or upper middle socioeconomic class. Most women in the abnormal BMI categories were from lower middle (overweight 66 [39.28%], obese 10 [31.25%]) or upper middle (overweight 61 [36.31%], obese 16 [50%]) socioeconomic groups in comparison with women with normal BMI, which were mostly from lower socioeconomic group (116 [58%]). This difference in social class was more marked in the groups of obese women. History of smoking was not present in any of the groups. All women were married and cohabiting.{Table 1}

[Table 2] shows the incidence of maternal complications in women in the three BMI groups. All maternal complications noted increased linearly with increasing BMI. The resulted odds ratio (OR) for preeclampsia were 2.13 (95% CI: 1.25-3.65) in overweight and 3.35 (95% CI: 1.45-7.73) in the obese group. For GDM, it was 3.14 (95% CI: 1.70-5.82) in overweight and 7.36 (95% CI: 3.11-17.45) in the obese group. A similar relationship was observed for PPH where the OR were 2.17 (95% CI: 1.23-3.83) in overweight and 3.01 (95% CI: 1.24-7.29) in the obese group. The incidence of postoperative wound infection were overlapping and not significantly different in the different BMI groups; OR - 1.69 (95% CI: 0.42-6.79) in overweight and 2.86 (95% CI: 0.53-15.25) in the obese group, with the highest proportion occurring in obese women 3 (12%).{Table 2}

[Table 3] shows the obstetrics complications in the three BMI groups. The frequency of IOL was highest among overweight women 76 (45.24%) with OR 2.35 (1.52-3.64), and it was 52 (26%) in women with normal BMI and was 12 (37.5%) in obese women with OR 1.71 (0.78-3.73). Percentage of failed IOL was highest among obese group 7 (21.87%); OR 4.20 (95% CI: 1.13-15.54) and was 27 (16.07%); OR 1.65 (95% CI: 0.75-3.62).

The chance of instrumental delivery decreased with increasing BMI whereas that of caesarean section, either elective or emergency, increased. Percentage of instrumental delivery was highest 23 (11.5%) in normal BMI group and was decreasing in overweight 15 (8.93%); OR 0.75 (95% CI: 0.38-1.49) and obese groups 2 (6.25%); OR 0.51 (95% CI: 0.11-2.29).{Table 3}

In contrast to women in normal BMI group, women who were obese were less likely to have instrumental delivery, but more likely to have caesarean section. Both elective and emergency cesarean sections were more common in the overweight and obese group. Women who were overweight had 2.79 times (95% CI: 1.66-4.71) higher risk of having an elective cesarean section, and 1.42 times (95% CI: 0.87-2.32) higher risk of an emergency cesarean section. The obese group had 3.84 times (95% CI: 1.69-8.75) higher risk of having an elective cesarean section, and 2.82 times (95% CI: 1.28-6.21) higher risk of an emergency cesarean section.

[Table 4] and [Table 5] show the results of neonatal outcomes in different BMI groups. Percentage of preterm birth at or before 34 weeks and after 34 weeks but before 37 weeks were 8 (4%), 6 (3.57%), 2 (6.25%), and 16 (8%), 14 (8.33%), 3 (9.37%) in normal, overweight and obese groups, respectively. After adjusting for confounders, the OR of having a preterm delivery at or before 34 weeks was 0.88 (95% CI: 0.30-2.61) and 1.6 (95% CI: 0.32-7.89) in overweight and obese groups respectively. For preterm birth after 34 weeks but before 37 weeks in overweight and obese groups it was 1.04 (95% CI: 0.49-2.21) and 1.19 (95% CI: 0.33-4.34) respectively. However, overweight and obese women faced an increased risk of indicated preterm delivery both before and after 34 completed weeks of gestation. Post term delivery was decreasing with increasing BMI after adjusting for confounders.{Table 4}{Table 5}

Although LBW (birth weight <2500g) seemed to be more common with higher BMI groups; 21 (10.5%) in normal, 29 (17.26%) in overweight and 7 (21.87%) in obese categories, it was found to be non-significant after adjusting for confounders, who had an OR 1.77 (95% CI: 0.97-3.25) and 2.38 (95% CI: 0.92-6.18) in overweight and obese groups respectively compared to normal. However, macrosomia (birth weight >4000g), was more common and significant in the overweight 23 (13.69%) and obese 9 (28.12%) groups with ORs of 3.36 (95% CI: 1.51-7.49) and 8.30 (95% CI: 2.99-23.03) respectively, compared with the normal BMI group 9 (4.5%).

Percentage of IUD rates were higher in the overweight 6 (3.57%) and obese 2 (6.25%) groups as opposed to 5 (2.5%) in the normal BMI group. However, the OR were not statistically significant in the overweight 1.44 (95% CI: 0.43-4.82) and obese 2.6 (95% CI: 0.48-14.01) group after adjusting for confounders.

Apgar score < 7 at 1 min was also statistically not significant in the three BMI groups although the percentage of low Apgar were higher in high BMI groups. Percentage of NICU admission was linearly increasing with increasing BMI; 19 (9.5%) in normal, 27 (16.71%) in overweight and 13 (40.62%) in the obese group. However, the OR for NICU admission was significant in the obese group only 6.52 (95% CI: 2.78-15.24) when compared to overweight group 1.82 (95% CI: 0.97-3.41).


National Family Health Survey (NHFS-3), India have reported an increase in the percentage of overweight and obese married women from 11% in NHFS-2 (2003-2004) to 15 % in NHFS (2005-2006). [1]

Body mass index is a better indicator of body composition than weight alone and there is a very good correlation between weight recorded at the first antenatal visit and the pre-pregnancy weight. This is also agreed in other studies. [4]

Most studies have used a retrospective cohort design using data from routinely collected hospital databases [2] or trial data (Weiss-FASTER trial) [3] having large no of sample size and data collected over many years. In neither case do the data reflect population trends. Our data set is small, but population based, reflecting the population of north India. We have restricted our data to 200 cases and 200 controls only, as the principal aim of this study was to examine pregnancy outcomes while minimizing the effects of changes in clinical practice and obstetric protocols over time, especially about IOL and cesarean deliveries which may have influenced some of the outcomes studied. Nevertheless, even this limited dataset, shows a rising incidence of obese women booking for antenatal care. In contrast with most retrospective studies, all pregnancy events were concurrently recorded thereby limiting recall bias. In our study, we found a linear relationship between increasing BMI and the risk of developing preeclampsia, GDM, failed IOL, caesarean section, both elective and emergency, PPH, abnormal birth weight and NICU admission. Thus, this study adds to the increasing body of evidence which suggests that maternal obesity predisposes women to complicated pregnancies and increased obstetric interventions.

Previous research has found a strong association between increasing BMI and pregnancy induced hypertension. A meta-analysis of the risk of preeclampsia associated with maternal BMI showed that the risk of preeclampsia doubled with each 5 to 7 Kg/m 2 increase in pre-pregnancy BMI. [4]

Maternal obesity is associated with an increased risk of diabetes, both pre-gestational diabetes and GDM. Compared with normal weight women (BMI - 25 kg/m 2 ), a recent meta-analysis of 20 studies demonstrated that the OR of developing GDM was 2.14 (95% CI: 1.82-2.53), 3.56 (95% CI: 3.05-4.21), and 8.56 (95% CI: 5.07-16.04) among overweight (BMI - 25-30 kg/m 2 ), obese (BMI - 30 kg/m 2 ), and severely obese women (BMI - 40 kg/m 2 ), respectively. [5] The reason obese women are at higher risk of developing GDM has yet to be fully delineated, but is likely related to an increase in insulin resistance.

We found a significant linear increase in mean postpartum blood loss with increasing BMI. It appears that women with higher BMI bled more at least in part due to the increased incidence of IOL and operative deliveries. Sebire et al. [2] observed a 70% increase in PPH.

Our results agree with earlier reports, which have shown an association between increasing BMI and interventions like induced labor, failed IOL and caesarean delivery. [2],[3],[9] Obese women are more likely than normal-weight women to have an IOL because of increased rates of obstetric complications and postdates. These women also had a higher incidence of failed IOL. [10] The causes of the increased operative delivery rate included increased planned elective cesarean section for predicted macrosomia, maternal request or obstetrician request. The increases in emergency cesarean sections were for no progress of labor and foetal distress mainly.

Our study failed to show any significant differences in the risk of preterm delivery in the different BMI categories. Our study showed that the percentage of preterm delivery was highest in the obese group, but it was mostly indicated preterm delivery and not a spontaneous one. [9] This may be due to associated pregnancy complications for which early termination of pregnancy was indicated. About intrauterine growth retardation measured by the adjusted birth weight, we found a positive association with maternal BMI. Both the risk of LBW and macrosomia was higher in high BMI groups. However, macrosomia was much more common in the obese (BMI ≥ 30) group. Several studies investigating the relationship of maternal obesity with fetal growth have shown that obese women have an 18-26% increased chance of delivering large for date infants, even after controlling for maternal diabetes. [2],[3]

Although there were too few women in the obese group, this study found an increased percentage of IUD in high BMI groups; 2 (6.25%) with OR 2.6 (0.48-14.01).The combination of rapid fetal growth induced by the endogenous hyperinsulinemia in obese women and the functional limitations of the placenta to transfer sufficient oxygen to meet the requirements of the fetus, might have led to hypoxia and death in some cases.

Recent review [11] on obesity and pregnancy has highlighted several issues relevant to research and management policy. First, the lack of standard definitions of overweight and obesity makes comparison of findings across studies difficult. While, most reports define obesity as an increased BMI of greater than or equal to 30 Kg/m 2 (IOM), others have defined it as increased waist circumference, increased waist-hip ratio or body weight of more than 90 Kg. This makes comparison of studies difficult and may have implications in the management of normal pregnancy as recommended gestational weight gain is dependent on women's pre-pregnancy BMI. Moreover, in most clinics, pre-pregnancy BMI is not recorded routinely, thereby making extrapolation of booking weight or women's recall of pre-pregnancy weight unreliable. Krishnamoorthy et al. [11] suggest that all pregnancies in obese women be acknowledged as high risk and managed according to strict guidelines.

As obesity is modifiable and preventable, preconception counseling, treatment of obesity before conception and creating awareness regarding associated health risks are highly desirable. Screening for hypertension and diabetes mellitus must be done before conceiving and in first antenatal check-up in women with high BMI. In the postpartum period, mothers should be encouraged for breast feeding and counseled to return to expected weight and BMI. To reduce increased rate of caesarean sections among obese women, the obstetrician should be cautious about the consequences of the obese post-cesarean pregnancy.

This study, like any other observational study of its kind, suffers from limitations. Firstly, the ideal time to record the baseline height and weight of a pregnant woman is before she has started gaining weight due to gestation. In our study we have relied on height and weight recorded in pre-pregnancy or in early pregnancy up to 12 weeks, before any real impact of gestational weight gain. Still, values recorded in early pregnancy remain an approximation of the pre-pregnancy weight, and, therefore, subject to bias. Furthermore, exclusion of all women who booked after 12 weeks of gestation could have resulted in selection bias, overweight or underweight women being systematically excluded from the dataset. Our study included only 200 women with high BMI, which is a very small number. Larger studies are, therefore, required further to investigate the results.


It can be concluded from this study that obese pregnant women are at a greater risk of preeclampsia, gestation diabetes, postpartum hemorrhage, fetal macrosomia and also intrapartum complications causing increased risk of both emergency and elective operative delivery. Detailed understanding of the pathophysiological link between obesity and various adverse pregnancy outcomes is needed. As it is modifiable and preventable, preconception counseling, treatment of obesity before conception and creating awareness regarding associated health risks are highly desirable.


The authors would like to thank Dr. Rajeev Ranjan, IGESIC Hospital, Delhi for his special contribution towards the statistical analysis of our study.


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