Baseline maternal weight is associated with adverse birth outcomes in Botswana

The impact of baseline maternal weight on birth outcomes has been well studied in high-resource settings, but limited data exist from low and middle income countries (LMIC) where there is a higher prevalence of malnutrition. The Tsepamo Study performed nationally-representative birth outcomes surveillance at 18 government hospitals in Botswana, including over 70% of all deliveries. For this analysis, multiple gestations, deliveries occurring outside the hospital, deliveries before 24 weeks gestational age (GA), and deliveries to women living with HIV were excluded. Baseline weight was the first recorded weight < 24 weeks GA. The primary outcome was a composite of severe birth outcomes (very preterm < 32 weeks GA, very small for gestational age (SGA) < 3rd percentile, stillbirth, or neonatal death < 28 days). Secondary outcomes included individual severe outcomes, preterm delivery (< 37 weeks GA), and macrosomia ( > 4000g at delivery). Log binomial regression estimated the unadjusted relative risk (RR) of each outcome by baseline weight category. A total of 137,964 women met inclusion criteria between August 2014 and December 2020; 97,859 (70%) had a weight measured before 24 weeks GA. Median baseline weight was 61 kg [interquartile range (IQR) 53-73 kg]. Compared with a baseline of 60-69 kg, maternal baseline weight < 60 kg was associated with increased risk of the composite of severe outcomes, driven primarily by an increase in very SGA (Table). Higher baseline weight (≥70kg) was not significantly associated with differences in the composite (Table), although it was associated with an increased risk of perinatal death and with macrosomia (Table). In Botswana, low maternal baseline weight was associated with an increased risk of severe birth outcomes, driven primarily by an increase in very SGA infants. Perinatal death and macrosomia were increased with higher maternal baseline weight. The study highlights the opportunities for nutrition optimization pre-conception and in early pregnancy.