First trimester subchorionic hematoma and early pregnancy loss in patients undergoing fertility treatment

To evaluate the association of subchorionic hematoma in early first trimester with early pregnancy loss in patients who conceived through assisted reproductive techniques versus spontaneous conception. A retrospective cohort study on 591 pregnancies resulting from frozen embryo transfer (FET), ovulation induction with intrauterine insemination (IUI) or timed intercourse (TIC), and spontaneous conception between 2015-2021 at Texas Children’s Family Fertility Center. Patients were included after an obstetric ultrasound showing the presence of fetal heartbeat at 6 weeks gestation and if delivery results were available. Those without documented pregnancy outcomes or without first trimester ultrasounds were excluded. The primary outcome was early pregnancy loss (EPL), defined as ultrasound confirmed spontaneous abortion at less than 20 weeks gestation. Demographics including age, BMI, diagnoses, obstetrical outcomes were collected. Presence, and largest dimensions of a SCH were recorded, along with presence/absence of vaginal bleeding. Baseline characteristics were compared using chi square and t-test statistics. Log-binomial regression test was used to adjust for baseline characteristics that were statistically significant. At our institution, 576 patients met study criteria (215 patients with SCH and 361 without). There was no significant difference in early pregnancy loss outcome for patients who were diagnosed with SCH (crude RR 0.658, 95% CI 0.40-1.07). The early pregnancy loss rates were 9% (live birth rate of 91%) for patients with SCH vs 14% (live birth rate of 86%) for those without SCH. The prevalence of SCH was 56% in pregnancies conceived by embryo transfer, 13% by IUI, 8.4% by TIC, and 23% by spontaneous conception. There was a significant difference in the rate of SCH depending on method of conception (FET 35% without vs 56% with SCH, IUI 21 % vs 3%, TIC 6.7 vs 8.4% or spontaneous conception 38 vs 23%, p<0.001). After adjusting for the conception method, there was no significantly increased risk of EPL (aRR 0.635, 95% CI 0.39-1.04). There was no difference in age (mean 34.8 vs 34.8 yr, p=0.863), body mass index (median 25.3 vs 25.3, p=0.560), delivery type of Cesarean or vaginal (p=0.213), presence of preterm delivery (11 vs 12%, p=0.682), presence of uterine factor diagnosis (31% vs 29%, p=0.58), endometriosis (9.1% vs 8.8%, p=0.166), or medical diagnosis (70% vs 76%, p=0.093) between patients with or without SCH. In a subgroup analysis of patients with SCH (n=215), there was no association between vaginal bleeding, size, or number of SCH with EPL (p=0.106) regardless of conception when controlling for age, BMI, and medical diagnosis. High rates of SCH were found in pregnancies resulting from embryo transfer compared to ovulation induction or spontaneous conception when assessed at early gestational age. However, there was no increased incidence of EPL in this group.