Background
Optimal pre-pregnancy body mass index (BMI) and optimal gestational weight gain (GWG) are vital in providing the nutritional demands in pregnancy required for foetal growth. The Institute of Medicine (IOM) guidelines provide recommendations of GWG based on each pre-pregnancy BMI category, and GWG outside the IOM recommendations can have adverse pregnancy outcomes for both the mother and the baby [1].
Methods
We performed a prospective study of 137 singleton pregnant women with metabolic risk factors, excluding pre-existing diabetes, and observed their pregnancy and delivery outcomes. Maternal parameters were assessed in early pregnancy (<20 weeks gestation) and between 26 - 28 weeks gestation. The rate of GWG was categorised as inadequate (In-GWG), normal (NL-GWG), and excessive (Ex-GWG) according to the IOM guidelines.
Results
Pre-pregnancy BMI was significantly correlated with rate of GWG (p=0.041); women with Ex-GWG had a higher pre-pregnancy BMI. Women with pre-pregnancy overweight BMI were more likely to have Ex-GWG (OR=4.08, p=0.026). Women of younger age (age<30 years), primiparous women and those with PCOS had no significant likelihood to develops Ex-GWG (OR=2.47, p=0.113; OR=1.32, p=0.542; OR=1.4, p=0.528 respectively). Women with Ex-GWG had a significant rise in mean fasting insulin in late pregnancy compared to early pregnancy (p<0.001). A significant proportion (77.3%) of large for gestational age (LGA) infants were born to women with Ex-GWG (p=0.047). The odds of LGA was higher in women with Ex-GWG (OR=9.15, p=0.037), but not significantly different in women with In-GWG (OR=5.25, p=0.155) compared to NL-GWG. There was no significant difference in odds of having small for gestational age (SGA) infants in women with Ex-GWG (OR=2.52, p=0.405) or In-GWG (OR=1.105, p=0.945) compared to NL-GWG. The likelihood of pre-term delivery was not significantly different in either Ex-GWG (OR=6.14, p=0.088) or In-GWG (OR=3.75, p=0.268) compared to NL-GWG. Women with Ex-GWG (OR=1.57, p=0.410; OR=1.26, p=0.695) and In-GWG (OR=1.32, p=0.672; OR=1.37, p=0.655) had no significant difference in odds to require caesarean delivery or have post-partum haemorrhage compared to women with NL-GWG.
Conclusion
Women with high pre-pregnancy BMI were more likely to have Ex-GWG. Women with Ex-GWG had a significant rise in fasting insulin level during pregnancy indicating development of insulin resistance. Women with Ex-GWG were more likely to have LGA infants. Measures should be taken to identify women at risk of excessive GWG to prevent the associated adverse pregnancy outcomes.