Fetal growth in women managed with insulin pump therapy compared to conventional insulin

Fetal hyperinsulinaemia secondary to maternal hyperglycaemia is considered to be the driving force behind excessive fetal growth. We hypothesised that insulin pump therapy (continuous subcutaneous insulin infusion, CSII) would improve maternal glycaemic control and normalise fetal growth parameters. To this end, this study compares maternal glycaemic control and fetal growth of women receiving insulin pump therapy with those receiving conventional insulin therapy.

Prospective non-randomised study of 42 women with pre-existing diabetes attending a joint obstetric diabetic clinic. Each woman was offered the choice of commencing insulin pump therapy or remaining on a conventional insulin regime. Estimated fetal weight and fetal growth velocity were calculated from routinely collected third trimester ultrasound biometry and expressed as standard deviation (Z) scores.

Eighteen women commenced insulin pump therapy. There was no difference in pre-conception glycosylated haemoglobin A1c concentrations (HbA1c) between pump and conventional therapy groups (mean HbA1c 7.62 versus 8.01; p=0.49) or third trimester glycaemic control (mean HbA1c 6.63 versus 6.44; p=0.51). Women using pump therapy had similar mean growth velocity Z scores (1.5 versus 1.36; p=0.83), similar mean estimated fetal weight Z scores prior to delivery (2.80 versus 2.16; p=0.16) and similar mean birthweight Z scores (2.09 versus 2.00; p=0.86) compared to women using conventional insulin therapy.

This small, non-randomised study suggests that the use of insulin pump therapy offers no benefit in terms of normalising fetal growth velocity, fetal size, birthweight or improving maternal glycaemic control compared to conventional insulin therapy.