Combining human placental lactogen with routine glucose challenge tests

Objective: To test the hypothesis that among gravidas with abnormal 1 hour glucose challenge tests (GCT), human placental lactogen (HPL) is higher for those found to have gestational diabetes.Study Design: Coincident with the GCT, serum was used to measure HPL by radioimmunoassay technique. Interassay and intraassay coefficients of variance were 6.0% and 1.4%, respectively. All GCT > 130 mg% were followed by a 100 g oral GTT (Carpenter criteria).Results: Two hundred fifty-seven women whose mean age was 29.4 years were studied. Twenty-two percent (57/257) had an elevated GCT. Forty-nine percent (25/57) of those with a positive screen were found to have an abnormal GTT. The mean HPL for this group of 25 women with gestational diabetes was 5.85 +/- 2.55 mg/mL and was significantly higher than the 3.38 +/- 1.40 mg/mL level in the 32 (32/57) women who had an abnormal GCT but a normal GTT, P =.034. The mean HPL for women who had a normal GCT screen was 4.68 +/- 1.64 mg/mL and was not statistically different from the HPL in women with an abnormal GCT but who had a normal GTT, P =.1. However, among the 11 women with a normal GCT but whose infants weighed >4000 g, the mean HPL was 5.83 +/- 1.29 mg/mL, which was similar to the mean HPL found in women with gestational diabetes.Conclusion: Our findings suggest that HPL levels are lower in groups of women with positive GCT but a negative GTT when compared to groups with a positive GCT but an abnormal GTT. Adjuvant HPL measurements may improve the positive predictive value of GCT.