The Effects of Pre-Pregnancy Body Mass Index and Gestational Weight Gain on the Risk of Preeclampsia at a Tertiary Referral Hospital, Northern Tanzania

Abstract Background: Pre/eclampsia and other hypertensive disorders of pregnancy contributed to 18% of the maternal mortality reported in Northern Tanzanian. There is increasing prevalence of obesity in Tanzania which is related to excessive weight gain in pregnancy. Both high BMI and excessive gestation weight gain are identified to increase risk of PE and subtypes, however this is still inconclusive and little is known about the joint effect of pre-pregnancy BMI and GWG on risk of PE and its subtypes in Africa. We evaluated the independent and joint effects of pre-pregnancy BMI and GWG on the risk of pre-eclampsia and its subtypes among women who delivered at Kilimanjaro Christian Medical Center (KCMC) from October 2018 to May 2019, Northern Tanzania.Methods: We performed a retrospective birth cohort study from October 2018 to May 2019 at KCMC, Tanzania. Pre-pregnancy BMI was categorized using WHO categories into Underweight (˂ 18.5kg/m²), Normal weight (18.5-24.9kg/m²), Overweight (25-29.9kg/m²) and Obese (≥ 30kg/m²). Gestational Weight Gain (GWG) was categorized using the 2009 Institute of Medicine (IOM) guidelines into Inadequate, Adequate and Excessive weight gain in pregnancy. Multinomial logistic regression analysis was used to adjust for confounders using relative risk, 95% confidence interval for the risk ratios (RR) that did not cross 1 and p<0.05 were regarded statistically significant.Results: Among the 1309 women analysed, 5.3% were Underweight, 51.1% Normal weight, 26.9% Overweight and 16.7% were Obese. About 43.5% had excessive GWG. Women with PE were 9.5%. Both obesity and excessive GWG independently increased risk of PE with adjusted RR=2.42, 95%CI: 1.48-3.96 and RR=1.77, 95%CI: 1.16-2.69 when compared to normal BMI and adequate GWG respectively. Jointly, Obesity and Excessive GWG had the highest risk of PE (ARR=4.95, 95%CI: 2.21-11.10). The increased risk was similar for Mild PE (MPE), Severe PE or eclampsia (SP/E) and Late Onset PE (LOPE). No association was found for Early Onset PE (EOPE).Conclusion: Pre-pregnancy Obesity and Excessive GWG independently and jointly increases risk for PE and the risk varies by PE subtype.