Fetal anterior wall thickness and amniotic fluid insulin levels: an interdependence?

PURPOSE: Excessive fetal fat as the hallmark of GDM pregnancy complications is one consequence of fetal hyperinsulinism. Noninvasive methods for fetal surveillance and measurement of fetal fat are needed. The purpose of this study was to test the hypothesis that measurements of the fetal anterior abdominal wall thickness (AAWT) in women with GDM will allow early detection of fetal hyperinsulinism.

MATERIALS AND METHODS: Amniocentesis was performed between 28 and 32 weeks of gestation (wks) in 220 women with GDM (diagnosed by 75 g oGTT at 24 to 28 wks). Amniotic fluid insulin levels (AFIL) were determined by a commercially available radioimmunoassay. Transabdominal ultrasound provided fetal biometric measurements following standard procedures and the AAWT including fetal skin and subcutaneous tissue at the time of amniocentesis. Maternal parameters (weight, BMI, oGTT blood glucose levels and mean daily blood glucose levels) were correlated with fetal biometric data and with AFIL.

RESULTS: There was no difference in AAWT in women with GDM and no correlation with mean AFIL. AFIL also did not correlate with any other fetal measurement or with mean oGTT blood glucose levels. AFIL only showed a correlation with maternal weight (p = 0.02) and maternal BMI (p = 0.01). The correlation was present for values both before pregnancy and at the time of amniocentesis.

CONCLUSION: In the early third trimester, AAWT measurements do not correlate with fetal insulin levels.