(1234) Trisomy 21 Fetal Growth: 18 Years of Sonographic Experience and Outcome Data

Fetal growth restriction (FGR) commonly features in Trisomy 21 (T21) but it is unclear if this reflects a separate pathology. As most T21 cases are terminated in the US, few data exist to guide clinicians on expected fetal growth. The different approach of our country offers opportunity for data on fetal growth in expectantly managed T21 cases. We reviewed serial fetal growth of ongoing T21 pregnancies using standard biometry (Hadlock-3 formulae).

Study Design:

Prenatally diagnosed T21 cases were identified from a prospectively collected registry with serial biometry extrapolated from Viewpoint 5® (abdominal circumference (AC), head circumference (HC), femur length (FL) and estimated fetal weight (EFW)). Postnatal diagnoses were included where third trimester biometry was recorded. Maternal demographics, pregnancy outcomes and placental histology were obtained. Resulting scatter plots for T21 pregnancies were generated.

Results:

A total of 114 cases of T21 (105 prenatal and 9 postnatal) were identified over an 18-year period (2006-2023). Outcome data are presented in Table 1. On compilation of growth centiles, a substantial proportion of EFW trended below the 50th percentile for gestation, particularly from 28 weeks (Figure 1). AC remained consistent in trajectory throughout pregnancy but all other growth parameters fell below the 50th percentile (Table 1). Umbilical artery Doppler abnormalities were seen in 19% (22/114) of pregnancies. Only 34% of pre-delivery EFWs and 31% of birthweights were below the 10th percentile for gestation. 30 placentas underwent histological examination with diverse abnormalities found in the majority, of which only one third demonstrated typical features of uteroplacental disease (Table 1).

Conclusion:

T21 pregnancies demonstrate unique growth patterns in-utero. Resulting centiles generated for T21 pregnancies in this study differ from those of euploid singleton norms, unexplained by uteroplacental disease alone. Customized prenatal centiles for T21 should be validated in future studies to inform the care of expectantly managed T21, particularly where FGR is co-existing.