The Effect of Fetal Trisomy 21 on Adverse Perinatal Obstetrical Outcomes in Nova Scotia, 2000-2019.

OBJECTIVE

To understand the risks associated with trisomy 21 in pregnancy in order to inform obstetrical care and improve outcomes.

METHODS

A population-based retrospective cohort study was undertaken of all pregnancies involving a fetus with trisomy 21 in Nova Scotia, Canada, from 2000 to 2019. Cases were identified from the provincial laboratory genetics database, linked to the Nova Scotia Atlee Perinatal Database for pregnancy outcomes, and compared with the general obstetrical population.

RESULTS

A total of 350 pregnancies were identified, of which 23% were ongoing pregnancies in which trisomy 21 was diagnosed prenatally and 24% involved diagnoses made after delivery. Compared with the general obstetrical population, women with ongoing pregnancies affected by trisomy 21 were more likely to be older (mean age 34 vs. 29 y), multiparous (67% vs. 55%), and in a relationship (79% vs. 68%). Trisomy 21 was associated with a significantly increased risk of preterm birth (<37 weeks; 24.1% vs. 8.3%); small for gestational age (<10th percentile; 21.7% vs. 8.2%); cesarean delivery (31.5% vs. 27.1%); and combined perinatal/neonatal mortality (8.0% vs. 0.8%) (P < 0.001 for all).

CONCLUSION

Trisomy 21 is associated with significant adverse perinatal and neonatal risks. Population screening to identify trisomy 21 can be used to optimize perinatal outcomes with appropriate fetal surveillance in these pregnancies.