PFM.63 Uncovering the complex relationships between maternal age, antenatal detection rates, and pregnancy outcome in cases of Trisomy 13 and 18 (T13&T18)

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Abstract

Background

Screening for T13&T18 is offered to all pregnant women as part of the UK Fetal Anomaly Screening Programme (FASP). Current targets require antenatal detection rates of 95%.

Aim

To explore the complex and changing relationships between antenatal diagnosis of T13&18, increasing maternal age and rates of termination over fifteen years using data from the East Midlands and South Yorkshire Congenital Anomaly Register. To compare this with Down syndrome (DS) data presented to BMFMS in 2013.

Methods

All cases of T13&18 delivered between 1998–2012 in the region were identified. Maternal age and pregnancy outcome were analysed, with mean gestational age at diagnosis calculated for each age group by cohort year.

Results

232 cases of T13 and 552 of T18 were identified (birth prevalence 2.32 and 5.52/10,000). 678/784 cases (86.5%: CI 83.9, 88.8) were diagnosed antenatally, at a mean gestational age of 16 weeks. Antenatal detection rates of both trisomies were similar across age groups, improving over time and reaching 91.5% (CI 84.8, 95.8) by 2011–2012. 81.0% (CI 77.8, 83.9) of cases diagnosed antenatally resulted in termination of pregnancy, which remained constant through time.

Conclusion

Currently, antenatal detection of T13&18 across the region is not significantly different from the FASP target. Whereas our previous work on DS demonstrated a change over time in detection and termination rates within the same cohort, based on maternal age, no such change is evident here. A number of possible explanations exist involving, inter alia, differing acceptance of termination of pregnancy for lethal and non-lethal anomalies.

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