# Association between gestational weight gain and adverse pregnancy outcomes: cohort analysis from South Asia and Sub-Saharan Africa

## TL;DR

This study finds that low weight gain during pregnancy is linked to higher risks of adverse outcomes like preterm birth and low birth weight in low-to-middle-income countries.

## Contribution

The study provides new evidence on gestational weight gain and pregnancy outcomes in South Asia and Sub-Saharan Africa.

## Key findings

- Lower gestational weight gain was associated with increased risk of preterm birth and low birth weight.
- The association between weight gain and adverse outcomes varied by maternal BMI category.
- Alternative measures of weight gain showed consistent results except for preterm birth with INTERGROWTH-21st Z-scores.

## Abstract

Studies of gestational weight gain (GWG) and adverse pregnancy outcomes seldom focus on low-to-middle-income countries (LMICs), despite their high burden of morbidity and mortality. We examined GWG patterns and adverse pregnancy outcomes in a consortium of pregnancy cohorts from LMICs.

We analysed data from five observational pregnancy cohorts in Bangladesh (two cohorts), India, Pakistan and Zambia. The study population comprised 15 286 singleton pregnancies with two or more maternal antenatal weight measurements. We estimated reference values for GWG using longitudinal models and calculated weight gain for gestational age Z-scores. We then estimated the associated risks of preterm birth, low birth weight, and small for gestational age, stratified by maternal body mass index (BMI), using marginal generalised linear models and plotted non-linear trends in the associations.

The median baseline maternal and gestational age were 24 years (IQR, 21–28) and 13 weeks (IQR 11–16), respectively, with 23% of participants having underweight BMI. The median GWG was 6.8 kg (4.2–9.4) and varied across cohorts from 6.1 kg (3.7–8.5; Bangladesh) to 7.0 kg (4.0–10.0; Zambia). The risk of preterm birth (13%) increased with lower GWG Z-scores among underweight (adjusted risk ratio (ARR), 1.4; 95% CI, 1.1 to 1.9 for lowest Z-score group) and normal BMI participants (ARR, 1.1; 95% CI, 1.0 to 1.2). The risk of low birth weight (25%) increased with lower GWG Z-scores in all BMI strata except obese participants (ARR, 1.7; 95% CI 1.5 to 1.9 among underweight). The risk of small for gestational age (36%) increased with lower GWG Z-scores in all BMI strata (ARR, 1.3; 95% CI 1.2 to 1.4 among underweight). In secondary analyses, alternative measures of GWG (adequacy ratio; INTERGROWTH-21st) had associations that were consistent with those from our study-specific Z-scores, except for a less clear association between preterm birth and INTERGROWTH-21st Z-score.

GWG was associated with preterm birth, low birth weight and small for gestational age. Early pregnancy BMI modified the association between GWG and outcomes in the study setting.