Large intrauterine haematomata in threatened miscarriage. Frequency and clinical consequences

Previously we described intrauterine haematomata seen with ultrasound in patients with threatened miscarriage and we suggested that a haematoma of greater than or equal to 50 ml might represent a risk to the pregnancy. We have now investigated 566 patients with vaginal bleeding in the first half of pregnancy and followed up 23 (4%) who had a haematoma of greater than or equal to 50 ml (mean 71 ml, range 50-150) at between 12 and 20 weeks gestation. One patient had a miscarriage and two had a preterm delivery, so that, contrary to our original suggestion, these large haematomata do not seem to represent any serious threat to the pregnancy.