Gestational diabetes mellitus and neonatal hyperthyrotropinemia

To determine whether gestational diabetes mellitus (GDM) is associated with increased incidence of neonatal hyperthyrotropinemia.

In a retrospective study, maternal characteristics, infant outcome and cord blood thyrotropin (TSH) concentration were compared between 469 diet-treated GDM pregnancies diagnosed by the World Health Organization 75 g oral glucose tolerance test (OGTT) with 474 non-diabetic pregnancies with normal OGTT results.

Hyperthyrotropinemia (TSH >16 mIU/l) was found in 7.2% of the GDM pregnancies and 2.1% of the controls (p < 0.001), but there was no difference in the birth weight or gestational age. The TSH concentration was correlated with the OGTT 2-hour glucose value (rho = 0.0948, p = 0.029) and Apgar score at the fifth minute (rho = -0.1197, p = 0.009). There was no difference in the TSH or free thyroxine concentrations between the hyperthyrotropinemic newborns of the GDM and control groups. In the GDM group, the hyperthyrotropinemic newborns had a higher incidence (p = 0.017) of neonatal jaundice.

Neonatal hyperthyrotropinemia is more frequently found in pregnancies with GDM, and this could have reflected increased fetal in-utero hypoxic stress in these pregnancies.