Can Early First Trimester Ultrasounds Correctly Determine Gestational Age Compared to Ultrasounds Performed Between 7...

The Society of Obstetricians and Gynaecologists of Canada (SOGC) recommends the use of an ultrasound performed between 7 and 14 weeks gestation to accurately predict gestational age (GA). This study aimed to assess the accuracy of earlier ultrasounds (5 to 6⁶ weeks gestation) by comparing the estimated delivery dates (EDD) in participants that had undergone both an earlier ultrasound and ultrasound completed during the standard of care timeframe.

EDD based on crown-rump length were retrospectively reviewed for patients that had undergone an ultrasound between 5-6⁶ weeks GA versus the recommended 7-14 weeks GA at the Montfort Hospital during 2018 and 2019. The charts of 981 patients that had an ultrasound prior to 7 weeks GA and at 7-14 weeks GA were reviewed; 54 were included.

There was no significant difference (P = 0.307) between the EDD of the early (5-6⁶ weeks GA) and the second ultrasound (7-14 weeks GA). The first ultrasounds were then separated into very early (5-5⁶ weeks GA) and early (6-6⁶ weeks GA) and compared. No significant differences (P = 0.579) were found. Similarly, no difference was found between the EDD of the early (6-6⁶ weeks GA) and standard of care timing (P = 0.324).

These results show no significant difference in accurately determining the EDD between ultrasounds completed at the early and standard of care time points. This could result in cost-saving benefits by foregoing a repeat ultrasound; however, further research is required prior to applying these findings in clinical settings.