(361) Dual positivity for Down syndrome and neural tube defects : Indicator of adverse pregnancy outcomes

Objective: ‘Dual positivity’ refers to screen-positive for both Down syndrome (DS) and neural tube defect (NTD) in second-trimester screening tests (Fetal Diagn Ther 1998;13:106–110). Given that alpha-fetoprotein (AFP) level is usually low in DS, the concurrence of high risk for both DS and NTD does not match each other. Herein, we aim to check the clinical significance of dual positivity associated with adverse pregnancy outcomes, including preeclampsia and fetal growth restriction (FGR).

Study Design: This retrospective study included 445 pregnant women whose serum marker tests indicated a high risk for DS (N=315), NTD (N=81), or both (N=49), who delivered at our institution between January 2014 and March 2024. Additionally, one hundred consecutive women with low-risk results for both DS and NTD during the study period were selected as a control group. We compared the rate of preeclampsia and FGR among four groups: control, high risk for DS, high risk for NTD, and dual positivity. We also examined the gestational age of delivery and neonatal birth weight. Statistical analyszes were performed using linear-by-linear analysis and ANOVA.

Results: Among the dual positivity group, no fetus was diagnosed as DS by amniocentesis nor NTD by level II ultrasonography. The rate of preeclampsia was highest in dual positivity (57.1%), followed by high risk for NTD (18.5%), high risk for DS (14.9%), and control (4%). Similarly, the rate of FGR was highest in dual positivity (79.6%), followed by high risk for NTD (40.7%), high risk for DS (17.1%), and control (6%). The median gestational age at delivery and neonatal birth weight of dual positivity group were 29+5 (interquartile range, 25+6-35+5) weeks and 0.94 (interquartile range, 0.45-1.96) kg, respectively, which was significantly lower compared with other three groups (Figure 1).

Conclusion: Our data indicate that dual positivity is strongly associated with preeclampsia or FGR. This suggests that women with dual positivity require enhanced prenatal care, including regular monitoring of maternal blood pressure and fetal growth assessments.