Perinatal outcomes in euploid pregnancies with 'double-positive' first trimester prenatal screening for trisomy 18 and 21

Objective:The objective of this study was to investigate whether women who screened positive for both trisomy 18 (T18) and trisomy 21 (T21) yet had euploid karyotypes were at increased risk for adverse pregnancy outcomes.Study Design:This was a retrospective cohort study of women who had first trimester aneuploidy screening. Double-positive subjects had risks greater than screening cutoffs for T21 and T18 and confirmed euploid karyotypes. Singleton subjects were matched 1:2 by maternal age to controls with normal screening. Perinatal outcomes were investigated using t-tests and χ 2 -tests; statistical significance was set at P<0.05.Result:Of 9733 women who had first trimester screening, 33 euploid pregnancies screened positive for both T21 and T18. Compared with controls, these study subjects were more likely to have abnormalities identified by prenatal ultrasounds, including renal, fetal membrane and fluid, as well as multiple anomalies (P=0.01). In addition, double-positive subjects had a lower mean gestational age at birth (P=0.02) and lower mean birth weight (P=0.03) than controls. Maternal outcomes were not significantly different.Conclusion:Pregnancies with double false-positive first trimester aneuploidy screening were associed with pregnancy/fetal abnormalities.