Amniotic fluid insulin values in women with gestational diabetes as a predictor of emerging diabetes mellitus.

Amniotic fluid insulin levels were estimated in 30 women with insulin-dependent diabetes, 216 with gestational diabetes and 27 with normal glucose tolerance. Results were correlated with birth-weight, incidences of fetal macrosomia and neonatal hypoglycaemia, and the risk of the mothers with gestational diabetes developing diabetes mellitus on follow-up. The women with prepregnancy diabetes had significantly higher amniotic fluid insulin values and showed a significant correlation between raised liquor insulin values (> 97th percentile) and hypoglycaemia in the infant (p = 0.039). In the gestational diabetic pregnancies there were highly significant associations between elevated liquor insulin values and macrosomia (p < 0.0045) and birth-weight (p < 0.00004), and a weak correlation with neonatal blood glucose levels (p = 0.042). Women with gestational diabetes who later developed permanent diabetes mellitus had higher mean amniotic fluid insulin levels than those whose glucose tolerance remained normal on follow-up (p < or = 0.0072) and more of them had a level greater than the 97th percentile than those whose glucose tolerance remained normal (odds ratio 6.48, 95% confidence interval 1.51-27.8, p = 0.0094). However a high amniotic fluid insulin level was of less clinical value for detection of women destined to develop diabetes (7 of 25, 28%) than was the need for insulin therapy during pregnancy (18 of 39, 46%).