Abstract

Dating ultrasounds for all women remains a goal of the National Maternity Strategy. We sought to examine the utility of guideline based first trimester scanning when performed in a tertiary maternity unit. We conducted a retrospective review of all public dating ultrasound scans over a one year period, reviewing 6,077 scans. Viability was confirmed in 97.9% (n=5953); 1.5% (n=94) were deemed non-viable, and 0.48% (n=29) required follow up for uncertain viability. There were 97.9% (n=5,951) singleton pregnancies, 1.8% (n=112) multiple pregnancies, and 0.2% (n=14) with an absent fetal pole. Of those attending for a first dating ultrasound, 81.7% (n=4,966) were between 10 and 13+6 weeks. 16% (n=977) of women relied on dating scans rather than last menstrual period to estimate gestational age. Overall, the mean difference between ultrasound scan and recalled menstrual dates was 3.9 gestational days. Other findings of significance included 0.4% (n=25) pregnancies with fetal anomalies diagnosed and 1.2% (n=78) of women were reported as having uterine anomalies. Conclusion: Dating ultrasound confirms viability, pregnancy number and due date. These factors are the basis of antenatal care. This study reinforces the need for routine scanning of all pregnancies in the first trimester.