Incidence, risk factors and pregnancy outcomes of gestational diabetes mellitus in Ibadan, Southwest Nigeria: a prospective cohort study

Abstract

OBJECTIVE: Gestational diabetes mellitus (GDM) is an emerging public health concern in low and middle-income countries, including Nigeria, because of the associated pregnancy complications, increased healthcare costs and long-term health sequelae among women of reproductive age and their offspring. We determined the cumulative incidence, risk factors and pregnancy outcomes of GDM in Ibadan, Nigeria. DESIGN: Prospective cohort study. SETTING: Ibadan, Southwest Nigeria. PARTICIPANTS: 721 pregnant women from the Ibadan Pregnancy Cohort Study participated in the one-step 75 g-oral glucose tolerance test at 24-28 weeks' gestation. OUTCOMES: The primary outcome of the study is the cumulative incidence of GDM. GDM was diagnosed according to the International Association of Diabetes and Pregnancy Study Groups criteria. Secondary outcomes were pregnancy outcomes, which included modes of delivery (CS, spontaneous vaginal delivery), macrosomia (birth weight ≥4.0 kg), gestational age at delivery and birth asphyxia. The risk factors (exposures) examined included sociodemographic, obstetric, clinical, behavioural and lifestyle factors. Bivariate and multivariate Log-binomial regression models were used to identify the independent risk factors of GDM (adjusted for maternal age ≥35 years, income, maternal body mass index, history of pregnancy loss and congenital anomaly) and the associated pregnancy outcomes of GDM (adjusted for maternal age, income and maternal body mass index). Adjusted relative risk (aRR) and 95% CI, used to assess the strength of associations, were reported. RESULTS: The cumulative incidence of GDM was 20.7%, 95% CI (17.9% to 23.9%). The mean time for the diagnosis of GDM is 25.4±1.42 weeks of gestation. After adjusting for other variables, maternal age ≥35 years: (aRR: 1.48). 95% CI (1.07 to 1.97) p=0.016), maternal obesity (aRR: 1.85, 95% CI (1.26 to 2.30) p=0.002) and a previous history of congenital anomaly (aRR: 2.83, 95% CI (1.97 to 4.07) p<0.001) were significantly associated with GDM risk. Women with GDM had a higher risk for elective CS: (RR 1.57 (95% CI: (1.04 to 2.36) p=0.032), the association was insignificant after adjustment for other variables (aRR 1.32 (95% CI: (0.86 to 2.03) p=0.199). CONCLUSION: The cumulative incidence of GDM is high among pregnant women in Ibadan. Maternal age ≥35 years, maternal obesity and a history of congenital anomaly were significant independent risk factors for GDM. These factors should be targeted for public health interventions, including lifestyle modification among pregnant women with obesity and early screening and diagnosis of GDM.