Impact of first-trimester aneuploidy screening in a high-risk population

To determine the impact on maternal decision-making of offering first-trimester screening to women at increased risk for fetal aneuploidy.

A retrospective chart review of all patients > or = 35 years of age at delivery who registered to deliver at Massachusetts General Hospital before (2000-2002; n = 1,604) and after (2003-2005; n = 1,915) the introduction of first-trimester screening. Demographics, the choice of screening test and/or invasive procedure (chorionic villus sampling or amniocentesis), and the detection rate of fetal aneuploidy were compared between the two groups by chi(2) test. Aneuploid newborns without an antenatal diagnosis were reviewed in detail.

The fraction of women who accepted prenatal screening and/or an invasive procedure increased from 1,122/1,604 (70%) to 1,751/1,915 (91%, p < 0.01) after the introduction of first-trimester screening. Fewer invasive procedures were done in the second time period, due to a decrease from 40 to 14% in the fraction of women going straight to an invasive procedure without screening (p < 0.01). Similar numbers of aneuploid fetuses were detected prenatally in the two time periods: 21/22 (95%) in the first time period and 22/25 (88%) in the second (p = 0.36). All 4 cases not prenatally diagnosed involved the patient's decision to decline screening or ignore positive screening results.

The introduction of first-trimester screening in a high-risk population was associated with an increase in the acceptance of prenatal screening and a reduction in the invasive procedure rate without a concomitant decrease in the detection of fetal aneuploidy.