were to determine the incidence of fibrinogen <2g/L in pregnancy, describe its causes, management and outcomes

A population-based cross-sectional study in the United-Kingdom was conducted. Any woman pregnant or immediately postpartum with a fibrinogen less than 2g/l was included. Data were collected via the UK Obstetric Surveillance System between November 2017 and October 2018 in any UK hospital with a consultant-led maternity unit. The main outcome measures was the incidence of low fibrinogen.

124 women with fibrinogen <2g/L were identified (1.7 per 10,000 maternities [95%CI 1.4 to 2.10]). Less than 5% of cases of low fibrinogen were due to preexisting inherited dysfibrinogenaemia or hypofibrinogenaemia. Eight percent of women had no hemorrhage. Biological patterns and the total blood loss varied according to the cause of low fibrinogen. Sixty percent of cases were due to PPH caused by placental abruption, atony or trauma. Amniotic fluid embolism and placental causes other than abruption were associated with the highest estimated blood loss (median 4400ml) and lowest levels of fibrinogen. Low fibrinogen also occurred among women in their 1st or 2nd trimester with 14 cases due to ruptured ectopic pregnancies, miscarriages and terminations of pregnancy before 22 weeks of gestation. Mortality was high with two maternal deaths due to massive PPH, 27 stillbirths and two neonatal deaths.

Fibrinogen <2g/L mostly affected women with PPH but also occurred among women in their 1st trimester of pregnancy. It was associated with extremely high maternal and perinatal mortality.