The effect of maternal weight on obstetric outcome

Nchinyani, Mokgadi Johannah
Journal Title
Journal ISSN
Volume Title
Background In a demographic health survey done in South Africa (2008), 25% of adults were classified as overweight and 20% were obese. Maternal obesity has been recognized as a risk factor for poor outcomes, such as gestational diabetes mellitus (GDM), fetal macrosomia, preeclampsia, stillbirth and post-term pregnancy in mothers and their babies. The main objective of this study was to describe the proportion of women with different BMI and obesity classes and the associated outcomes in pregnant women in Soweto between March 2011 and August 2012. Methods This is a cross-sectional study using secondary data collected between (March and June) 2011 and (March and August) 2012 in two randomised controlled trials assessing the efficacy of trivalent inactivated influenza vaccine. Pregnant women were recruited at Chris Hani Baragwanath Academic hospital and at midwife obstetric units in Soweto and mothers and babies were followed up for 24 weeks postpartum. For this study we used data collected at the baseline and delivery visits. Pregnant women aged between 18 and 39 years were included in the study. Ethics approval for this study and both previous studies was obtained from Human Research Ethics Committee (M101106, M101107 and M151033). Results Of the 2310 women recruited between 20 and 36 weeks gestation, 488 were excluded from the study (no heights/weights recorded).The median maternal age was 25.4 years [IQR 22-30; range 18.2- 38.3]. The median parity was 1[IQR 0-1; range 0- 4] and median gravidity was 2[IQR 1-2; range1- 5]. More than 99% (1817) of the women enrolled on the trials were black, 0.2% (3) coloured and 0. 1% (1) was Indian. HIV infection was present in 172(9.6%) women. The proportion of women in different BMI categories is as follows; underweight - 18(1%), normal weight- 516(28.3%), overweight- 649(35.6%) and obese - 639(35.1%). The median gestational age at birth was 38.7[IQR 37.1- 40.0; range 28.3- 42.7] weeks. The median systolic BP was 112 mmHg [IQR 104-121; range 89 – 142] and the median diastolic BP was 70 mmHg [IQR 62 – 75; range 50- 91]. More women in the obese group had experienced a previous miscarriage (93; 14.6%) compared to women of normal weight (52; 10.1%; p= 0.09). There was no difference in BMI of women who had suffered a previous neonatal death (55; 3.0%) or stillbirth (37; 2.0%; p=0.55). Obese women (468; 38.2 %) were significantly more likely to be referred to hospital for delivery than women of normal weight (325; 26.5; p=0.00). Women with an increased BMI (overweight or obese) were more likely to require caesarean section overweight (187; 28.8%), obese (232; 36.3%) (p- =0.00) than the other categories; underweight (4; 22.1%), normal weight (112; 21.7%). The mean birth weight in the different BMI categories was; underweight 2.7 kg(±0.3), normal weight 2.9 kg(±0.5), overweight 3.0 kg(±0.5) and in obese group 3.1 kg(±0.5), with p=0.00. The mean birth length in the different BMI categories was; underweight 48.1 cm(±3.0), normal weight 49.3 cm(±3.7), overweight 49.6 cm(±4.0) and in the obese group 50.0 cm(±4.1), with p = 0.01. The mean one minute Apgar scores 8 (±1.2) and five minute 9 (±0.9) and there was no difference in APGAR scores with different BMI categories. Women in obesity Class III were older and had more ultrasound examinations (39; 55%) compared to women in Class I (143; 36.8%). Conclusion Obese women were more likely to be delivered by caesarean section and had a history of poor obstetric outcome. Obesity was associated with increased systolic and diastolic blood pressures; however, this was not clinically significant. Obese women were more likely to be having a hospital delivery than women delivering at MOUs.
A Dissertation submitted to the Faculty of Health Sciences in fulfilment of the requirements for the degree Masters of Medicine (Obstetrics & Gynaecology) and the FCOG (SA), 2018