Background: Falling insulin requirements during pregnancy is thought to signify adverse outcomes, often prompting intervention. However evidence supporting this practice remains limited.
Objective: To investigate the clinical significance of falling insulin requirements in women with pre-gestational or overt diabetes in pregnancy.
Methods: This is a retrospective case control study of 140 pregnancies, in women with diabetes, presenting for antenatal care between 2010–2012. Women with a fall in insulin requirements of 15% or more from the peak total daily dose in late pregnancy were considered cases (n=33). The primary outcome was a composite of outcomes chosen to reflect clinical evidence of placental dysfunction including preeclampsia, intrauterine growth restriction, stillbirth (>20 weeks), premature delivery (<32 weeks) and a high systolic to diastolic ratio on umbilical artery doppler.
Results: 23.6% of women had more than 15% fall in insulin requirements with nulliparity as the only independent predictor at baseline (OR 2.4; CI 1-5.7, p =0.045). Amongst women with type 2 diabetes, those diagnosed with overt diabetes during pregnancy had an increased risk of falling insulin requirements (OR 4.3; CI 1.2 – 15.2, p=0.023) however, there was no difference between women with type 1 or type 2 diabetes. While falling insulin requirements was associated with an increased risk of preeclampsia (OR 3.7; CI 1.2-11.4, p=0.042) and the composite of clinical markers of placental dysfunction (OR 2.7; CI 1.2 – 6.1, p=0.028) it was not associated with adverse neonatal outcomes. However, there was a higher rate of neonatal intensive care unit admission (23.5% vs 1.9%, p <0.001) and earlier delivery in this group (median 37.8 weeks IQR (35.9-38.4) vs 38.3 IQR (37.3-38.9), p=0.046).
Conclusion: Falling insulin requirements, in women with pregestational diabetes is associated with an increased risk of complications due to placental dysfunction. The risk of adverse neonatal outcomes was not increased, however this may have been due to clinical intervention. Further prospective studies are needed.