Impact of a Routine Third Trimester Ultrasound Policy on Obstetric, Neonatal and Service Delivery Outcomes in an...

Routine third trimester ultrasound scans have been introduced in several maternity centres to increase detection of fetal growth disorders and improve perinatal outcomes.

To assess changes in obstetric and neonatal outcomes and service delivery following implementation of a routine third trimester ultrasound policy in a tertiary hospital in Australia.

A single-centre retrospective cohort study was conducted comparing a pre-policy cohort that received ultrasound scans measuring biometry and fetal Dopplers when deemed clinically necessary during the third trimester with a post-policy cohort in which all pregnant women were offered an ultrasound at 35-37 weeks gestation. Results of the ultrasound were communicated to the obstetric team. Primary study outcomes were changes to service delivery, obstetric and neonatal outcomes and detection of fetal growth abnormalities. Differences in proportions were compared using the chi-squared test.

In the pre-policy cohort, there were 4826 singleton deliveries ≥ 35 weeks gestation and 34% of these women received a third trimester scan, compared to 4499 deliveries in the post-policy cohort in which 81% received a scan. There was a statistically significant increase in detection of LGA fetuses from 27% to 43% but no significant change in SGA detection or preterm birth rates post policy implementation. Early term births (37-38 + 6 weeks) increased (26.9% vs. 31.2%; p < 0.001) along with induction of labour (33.5% vs. 38.2%; p < 0.001). There was no decrease in stillbirths or adverse neonatal outcomes.

The benefits of implementing routine third trimester scans in 'real-world' clinical practice remain unclear given these findings.