Introduction
There is concern that insulin use in gestational diabetes (GDM) may promote excess weight gain and thereby increase, rather than ameliorate the risk of pregnancy complications. We sought to evaluate the relationship between excess weight gain, insulin requirements and glycaemic control in pregnancy for women with GDM.
Methods
Women with GDM were recruited from a Sydney teaching hospital over a 1 year period. Insulin was routinely prescribed to those who did not meet ADIPS glucose targets. Data collected included prepregnancy weight and BMI, weight at 24 and 36 weeks, insulin requirements and HbA1c. Weight gain was categorised as within or greater than recommended as per Institute of Medicine (IOM) criteria (1). T-tests were used to compare HbA1c and total insulin used in those who gained excess weight versus those who did not.
Results
The population comprised 123 women, mean age 31.3 ±5.0 years. HbA1c was 5.8±0.6% at 36 weeks. Prepregnancy weight was 73.5±20.0kg, with BMI 28.3±6.5. At 36 weeks the total pregnancy weight gain was 10.0±8.6kg. Excess weight gain from baseline to 36 weeks occurred in 41% of women. Women who gained excess weight had higher total daily insulin requirements compared to those who remained within weight targets (56.3±63.3 vs 35.0±35.3 units, p=0.04) but also borderline higher HbA1c (mean 5.9±0.6 vs 5.7±0.6%, p=0.08). Excess weight gain between 24-36 weeks was similarly associated with higher HbA1c (6.5 ±0.5 vs 5.5±0.3%, p<0.01), higher baseline BMI (30.8±6.5 vs 27.2±6.2, p<0.01) but not higher insulin use (50.3±65.1 vs 38.5±37.2 units, p=0.285)
Conclusion
Women who gain excess weight during pregnancy have higher insulin requirements, higher HbA1c and are more overweight pre pregnancy. This suggests weight gain is not necessarily driven by insulin, but perhaps the need for higher insulin usage in some women is driven by inadequate control and issues related to body weight.