Difference between mean gestational sac diameter and crown-rump length as a marker of first-trimester pregnancy loss after in vitro fertilization

Abstract

Objective: To investigate whether the difference between mean gestational sac diameter and crown-rump length (mGSD - CRL) is associated with first-trimester pregnancy loss or adverse pregnancy outcomes after in vitro fertilization (IVF) and to determine if mGSD - CRL is a better predictor of pregnancy loss than either measurement alone.

Design: Retrospective cohort study.

Setting: University hospital.

Patient(s): A total of 1,243 IVF cycles with fresh or cryopreserved autologous embryo transfers resulting in singleton gestations performed at the University of Iowa Hospitals and Clinics from January 2005 through December 2014. Cycles included ultrasound measurements of mGSD and CRL at 45-56 days' gestation.

Intervention(s): Mean gestational sac diameter to crown-rump length difference.

Main outcome measure(s): Primary outcomes were first-trimester pregnancy loss and gestational age at delivery. Secondary outcomes were infant birth weight and pregnancy complications.

Result(s): First-trimester pregnancy loss rates were significantly higher in pregnancies with mGSD - CRL <5 mm (43.7%) compared with 5-9.99 mm (15.8%), 10-14.99 mm (9.9%), and ≥15 mm (7.1%). No correlations were found with infant birth weight, gestational age at delivery, or other pregnancy complications. mGSD - CRL was not a better predictor of pregnancy loss than mGSD or CRL alone.

Conclusion(s): There is a strong inverse relationship between mGSD - CRL and first-trimester pregnancy loss in IVF patients, although the incidence of pregnancy loss with a mGSD - CRL <5 mm was significantly lower than previously reported. Small mGSD - CRL was not associated with an increased risk of complications in pregnancies that continued beyond 20 weeks. The association between mGSD, CRL, and miscarriage is complex.

Keywords: IVF; Miscarriage; crown-rump length; gestational sac.

Figure 1:. Pregnancy loss rates by mGSD-CRL category

P values presented are for chi-square tests, compared to the 5–9.9 mm referent population.mGSD-CRL = mean gestational sac diameter to crown-rump length difference. *P<.001;**P<.007; ***P<.018.