Macrosomia despite good glycaemic control in Type I diabetic pregnancy; results of a nationwide study in The Netherlands

Aims/hypothesis. To investigate the incidence of foetal macrosomia (i.e. birth weight >90th percentile) in a non-selected nationwide cohort of women with Type I (insulin-dependent) diabetes mellitus in The Netherlands and to identify risk indicators predictive for macrosomia. Methods. We conducted a prospective nationwide cohort based survey regarding the outcome of Type I diabetic pregnancy in The Netherlands. Data of 289 women who gave birth to a live singleton infant without major congenital malformations at more than or equal to 28 weeks of gestation are shown. Results. The incidence of foetal macrosomia was very high (48.8%), with 26.6% of infants weighing more than 97.7th percentile. Glycaemic control during pregnancy was good (i.e. mean HbA_1c ≤7.0%), in almost all (84%) women. Multiple logistic regression analysis resulted in a predictive model for macrosomia that incorporated five variables: third trimester HbA_1c (Odds Ratio [95% Confidence Interval]: (1.6[1.1-2.4]), absence of third trimester severe hypoglycaemia (3.0[1.2-7.3]), the use of insulin lispro (3.1[0.9-10.4]), weight gain during pregnancy (1.1[1.0-1.2]) and non-smoking (2.8[0.9-9.3]). Third trimester HbA_1c was the most powerful predictor for the occurrence of macrosomia, but its predictive capacity was weak (explained variance <5%). Conclusion/interpretation. Despite apparent good glycaemic control, the incidence of foetal macrosomia in this non-selected prospective nationwide cohort of 289 Type I diabetic women was very high. Third trimester HbA_1c was the most powerful predictor, but its predictive capacity was weak. Thus, future research should focus on new more detailed glucose monitoring techniques (such as a continuous glucose monitoring system) as well as to alternative factors to reduce macrosomia.