OBJECTIVE: Is there an association between intrauterine haematoma (IUH) and pregnancy outcomes in patients who undergo fetal reduction after double embryo transfer (DET), and if so, what is the relationship between IUH-related characteristics and pregnancy outcomes?
METHODS: Clinical information and pregnancy outcomes of women who underwent fetal reduction after DET were analysed. Patients with other systematic diseases, ectopic pregnancy or heterotopic pregnancy, monochorionic twin pregnancies and incomplete data were excluded. Stratification of IUH pregnancies was undertaken based on IUH-related characteristics. The main outcome was incidence of fetal demise (<24 weeks), with other adverse pregnancy outcomes considered as secondary outcomes.
RESULTS: Thirty-four IUH patients and 136 non-IUH patients who underwent fetal reduction after DET were included based on a 1:4 match for age, cycle type and fertilization method. IUH patients had a higher incidence of early fetal demise (20.6% versus 7.4%, P = 0.048), threatened abortion (48.1% versus 10.3%, P<0.001) and postpartum haemorrhage (PPH; 14.8% versus 4.0%, P = 0.043) compared with non-IUH patients. IUH was an independent risk factor for early fetal demise [adjusted OR (aOR) 3.34, 95% CI 1.14-9.77] and threatened abortion (aOR 8.61, 95% CI 3.28-22.61) after adjusting for potential confounders. IUH pregnancies undergoing fetal reduction that resulted in miscarriage had larger IUH volumes and earlier diagnosis (both P < 0.03). However, IUH characteristics (i.e. volume, changing pattern, presence or absence of cardiac activity) were not associated with threatened abortion or PPH.
CONCLUSIONS: Fetal reduction should be performed with caution in IUH pregnancies after DET as the risk of fetal demise is relatively high. Particular attention should be given to IUH patients with early signs of threatened abortion and inevitable fetal demise.

The objective of our meta-analysis was to estimate the effect of intrauterine hematoma (IUH) on obstetric and pregnancy outcomes of assisted reproductive technology (ART) pregnancies. Four electronic databases were searched up to December 2021 to find studies reporting relevant outcomes of ART pregnancies with IUH. Dichotomous data were expressed as odds ratios (OR) with 95% confidence intervals (CI). Continuous data were expressed as weighted mean difference (WMD) with 95% CI. A total of six observational studies were included in this meta-analysis. Our data suggested that IUH in pregnancies achieved by ART are not associated with increased risks of miscarriage, low birth weight, placenta previa, or premature rupture of membranes. Similar birthweight was noted between the two groups. However, IUH was associated with significantly shorter gestational age at delivery (GA) as well as higher risks of preterm birth. Subgroup analyses have found that the presence of retroplacental haematoma was associated with an increased risk of miscarriage. IUH may be associated with decreased GA and an increased risk of preterm birth. Therefore, Women diagnosed with IUH should be offered increased surveillance during the course of their pregnancy.

In this study, the clinical significance of first-trimester intrauterine haematomas (IUH) detected in pregnancies achieved by IVF-embryo transfer (IVF-ET) was evaluated. A retrospective case-control study was designed to compare obstetric and perinatal outcomes of 350 pregnancies with IUH and 350 matched controls without IUH. The incidence of first-trimester IUH detected in the IVF-ET pregnancies was 13.5%. In women who delivered after 28 weeks\' gestation, the incidence of gestational hypertension (OR 2.6; 95% CI 1.5 to 4.6), preeclampsia (OR 2.8; 95% CI 1.5 to 5.0) and postpartum haemorrhage (OR 3.1; 95% CI 1.8 to 5.3) was significantly higher in the IUH group. Compared with controls, placenta previa (OR, 8.7 95%; CI 3.4 to 22.2) and oligohydramninos (OR 5.8; 95% CI 2.4 to 14.0) were more common in the IUH group. The incidence of preterm delivery (<37 weeks\' gestation) was significantly higher in the IUH group (OR 2.1; 95% CI 1.4 to 3.0), although the incidence of preterm delivery before 34 weeks\' gestation was not. No differences were observed in the incidence of gestational diabetes mellitus, premature rupture of membranes and low birth weight. The presence of first-trimester IUH in IVF-ET pregnancies was associated with a higher risk of several pregnancy complications.