Gestational diabetes diagnosed in third trimester pregnancy and pregnancy outcome

The clinical significance of gestational diabetes diagnosed in the third trimester is unclear. A prospective observational study was performed on a cohort of women without pre-existing gestational diabetes or other medical disorders to examine the effect of gestational diabetes on pregnancy complications and infant outcome.

Four hundred and eighty-nine consecutive women were assessed at 28-30 weeks by random glucose screening and/or a 75 g oral glucose tolerance test. The subsequent management was according to established departmental protocols. The outcome of pregnancy was compared among the groups with negative screening, positive screening but normal glucose tolerance, and gestational diabetes which was controlled with diet therapy.

Women with gestational diabetes (n=67 or 13.7%) had significantly increased maternal age, pre-pregnancy weight and body mass index, hemoglobin levels at booking and at 36-38 weeks, and incidences of parity >1, pre-eclampsia, and female infants, while the gestational age was shorter and there was no significant difference in the birthweight outcome or neonatal morbidity.

Despite diet treatment, gestational diabetes diagnosed in the last trimester is associated with increased risk of pre-eclampsia and shorter length of gestation, and this is likely to reflect a pathological process rather than the physiological effect of pregnancy on maternal glucose tolerance.