Prevalence of gestational diabetes mellitus and the effect of weight on measures of insulin secretion and insulin resistance in third‐trimester pregnant rural women residing in the Central Region of Limpopo Province, South Africa

Abstract

To examine the prevalence of gestational diabetes in third-trimester pregnant women as well as to assess their insulin secretion and insulin resistance (IR). Third-trimester pregnant women (n= 262) attending antenatal care at local clinics in the central region of the Limpopo Province underwent a 2-h oral glucose tolerance test (OGTT) with blood collected at 0, 30 and 120 min. Glucose and insulin were measured. The prevalence of gestational impaired glucose tolerance (GIGT) and gestational diabetes mellitus (GDM) was 8.8% (7.3% GIGT; 1.5% GDM). Women with GIGT/GDM were significantly older and had more children compared with women with a normal response to the OGTT. Homeostasis model assessment(HOMA)-IR and fasting insulin were lower in the GIGT/GDM group compared with the normal group, as were measures of insulin secretion (HOMA B-cell function and insulinogenic index). Furthermore, women with body mass index (BMI)> or =30.0 kg/m2 were significantly older and had higher parity, systolic and diastolic blood pressure measurements than those with BMI 25.0-29.9 kg/m2 and BMI < 25.0 kg/m2. However,increased BMI was not associated with an increased risk of GIGT/GDM. The present study shows that there is a high prevalence of GIGT/GDM, with most women having IGT. The GIGT/GDM present in these women is characterized by increased insulin sensitivity accompanied by reduced pancreatic B-cell function. Additionally, heavier women appear to have increased first phase insulin secretion, suggesting the presence of insulin resistance.