The influence of maternal insulin-dependent diabetes on fetal nuchal translucency thickness and first-trimester maternal serum biochemical markers of aneuploidy

Objective To evaluate the influence of maternal insulin dependent diabetes mellitus (IDDM) on maternal serum free β‐hCG, PAPP‐A and fetal nuchal translucency (NT), thickness at 11 to 13+6 weeks of gestation in a large cohort of women screened prospectively for chromosomal anomalies. Methods Information on maternal IDDM status, maternal serum biochemical marker levels and fetal NT were collected from the prenatal screening computer records in two first‐trimester screening centres. In total the control group included 33 301 pregnancies of which 16 366 had NT and maternal serum biochemistry results and 16 305 with NT only. The IDDM group included 195 pregnancies of which 79 had NT and maternal serum biochemistry results and 127 with NT only. The median maternal weight corrected free β‐hCG and PAPP‐A, expressed as multiple of the median (MoM), and fetal NT, expressed as delta values, in the IDDM and non‐IDDM groups were compared. Results There were no significant differences between the IDDM and non‐IDDM groups in median maternal weight corrected free β‐hCG (IDDM 0.87 MoM, 95% Confidence Interval 0.75 to 1.16 MoM, non‐IDDM 1.00 MoM), median maternal weight corrected PAPP‐A (IDDM 1.02 MoM, 95% Confidence Interval 0.83 to 1.05 MoM, non‐IDDM 1.01 MoM), or mean delta NT (IDDM 0.0358 mm, non‐IDDM 0.0002 mm). Conclusions In pregnancies with maternal IDDM, first‐trimester screening for chromosomal defects does not require adjustments for the measured fetal NT. However, more data are required before the possible reduction in maternal serum free β‐hCG and the reduction of PAPP‐A suggested by the published world series can be considered sufficiently important to take into account in the calculation of risks for chromosomal defects. Copyright © 2005 John Wiley & Sons, Ltd.