The chorionic bump is a predictor of miscarriage: a retrospective analysis of 13,656 in vitro fertilization...

To determine the prevalence of an ultrasound-defined chorionic bump (CB) in an in vitro fertilization (IVF) population and its association with clinical loss, preterm delivery, and additional pregnancy complications.

Retrospective cohort study.

Single, euploid, frozen embryo transfers (FETs) using autologous oocytes that underwent intracytoplasmic sperm injection and preimplantation genetic testing for aneuploidy at a single IVF institution.

The presence of a CB on ultrasound.

The primary outcome was clinical loss rate. Secondary outcomes included cumulative live birth rate, rates of preterm delivery (<37 weeks) and full-term delivery (>37 weeks), mode of delivery, gestational age at delivery, birthweight, placental abruption, first-trimester vaginal bleeding, gestational diabetes, intra-amniotic infection, hypertensive disorders of pregnancy, and retained products of conception at time of delivery. Subgroup analysis was also performed of only the first FETs.

There was an increased risk of clinical loss in IVF pregnancies with a CB (24.1% vs. 13.6%, P<.0001), but no association with other pregnancy complications. The results remained consistent in a subgroup analysis of only the first FETs.

Although there is an increased risk of first-trimester miscarriage with a CB, if the pregnancy persists, it is likely to result in a full-term delivery without additional pregnancy complications. This has important implications for counseling patients when faced with this rare pregnancy ultrasound finding.