Prediction of fetal loss by first-trimester crown–rump length in IVF pregnancies

Objective: To evaluate the association between small crown–rump length (CRL) and fetal loss ≤22 weeks in IVF pregnancies. Methods: A retrospective analysis of prospectively collected data at a university-affiliated medical center. All singleton IVF pregnancies within a 5-year period, with a live embryo on first-trimester ultrasound and verified pregnancy outcome were included. Rates of fetal loss ≤22 weeks were compared between pregnancies with a CRL ≤tenth percentile and above the tenth percentile of our population. Results: Overall, 397 pregnancies met inclusion criteria. Ninety-five percent of CRL measurements were performed at 40–80 gestational days. All live-embryo’s CRL measurements, from 40 to 80 mm, were plotted against expected gestational age (in 5-day clusters), with calculation of the tenth percentile for every gestational age. Total of 64 pregnancies had CRL ≤tenth percentile for gestational age. The rate of fetal loss in this group was significantly higher than in pregnancies with CRL >tenth percentile (17.2 vs. 6.6%, p = 0.005, OR = 2.93, 95% CI 1.2–6.7). In both groups, the majority of fetal losses occurred ≤10 weeks of gestation. Conclusion: In IVF pregnancies with a live embryo, a small CRL at 40–80 days’ gestation may predict fetal loss. Repeated ultrasound should be considered after 1–2 weeks.