Growth trajectory and miscarriage diagnosis threshold in early IVF pregnancy: multicenter study

To characterize early-pregnancy ultrasound findings in pregnancies conceived via in-vitro fertilization (IVF) for which gestational age is known precisely based on the date of embryo transfer (ET), and to examine their association with first-trimester pregnancy outcome.

This was a retrospective multicenter cohort study of fresh- and frozen-cycle IVF pregnancies from 14 centers across England between January 2022 and December 2024, with one center contributing additional data from January 2019 to December 2021. Patients with a confirmed intrauterine pregnancy at the first transvaginal ultrasound scan (≤ 9 + 6 weeks' gestation) after ET were included for analysis of pregnancy outcome. Data collected included the date of ET, embryo stage at transfer, early-pregnancy ultrasound measurements, including crown-rump length (CRL) and mean sac diameter (MSD), and expected gestational age. The endpoint was viability at the 11-14-week dating scan. CRL growth was modeled against gestational age using quadratic regression. The diagnostic performance of a range of gestational-age cut-offs for identifying miscarriage was evaluated using sensitivity, specificity and positive predictive value (PPV).

A total of 10 009 IVF pregnancies were included, of which 8223 (82.2%) were viable at 11-14 weeks and 1786 (17.8%) were non-viable. A significant difference was found in the distribution of CRL measurements at the first ultrasound scan between pregnancies that were found to be viable and those that were non-viable at the subsequent 11-14-week scan (P < 0.001). When stratified by gestational age based on the date of ET, viable pregnancies had a higher median CRL than pregnancies of the same gestational age that subsequently ended in miscarriage, although there was a degree of overlap in the distribution of CRL values between the two groups. Furthermore, among pregnancies that were viable at 11-14 weeks, significant variability was seen in CRL and MSD measurements at each gestational age. The estimated mean CRL growth rate was 0.926 mm/day from when CRL was first measurable. The ultrasound finding of an empty gestational sac at or beyond 47 days' gestation based on the date of ET (n = 406) had a PPV of 100% and specificity of 100% (95% CI, 94.9-100%) for first-trimester miscarriage.

Early-pregnancy ultrasound measurements in IVF pregnancy show wide physiological variability at any given gestational age, even when gestational age can be calculated precisely from the date of ET. An empty gestational sac at or beyond 47 days' gestation was associated with 100% PPV and 100% specificity for non-viable pregnancy. Further external validation in independent cohorts is required to confirm this potential threshold for diagnosing miscarriage in IVF pregnancy. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.