Variations in antenatal management and outcomes in haemolytic disease of the fetus and newborn: an international, retrospective, observational cohort study.

Background: Advances in haemolytic disease of the fetus and newborn have led to numerous treatment options. We report practice variations in the management and outcomes of haemolytic disease of the fetus and newborn in at-risk pregnancies.

Methods: In this international, retrospective, observational cohort study, data from cases with moderate or severe haemolytic disease of the fetus and newborn were retrieved from 31 centres in 22 countries. Eligible participants had pregnancies with haemolytic disease of the fetus that led to fetal death at 16 + 0 weeks or later, those treated antenatally with intrauterine transfusion or intravenous immunoglobulins, or neonates without antenatal treatment who were treated with intensive phototherapy, exchange transfusion, or red blood cell transfusions. All patients had confirmed maternal alloantibodies and an antigen-positive fetus incompatible with the maternal alloantibody. Patients with ABO-incompatibility only were excluded. We assessed serological diagnostics and referrals, antenatal treatment and timing, complications, delivery route, and gestational age at birth. Outcomes were analysed in all eligible participants who had complete data available.

Findings: 2443 pregnancies with haemolytic disease of the fetus and newborn treated between Jan 1, 2006, and July 1, 2021, were shared by the centres and analysed between Dec 1, 2021, and March 1, 2023. 23 pregnancies were excluded due to missing information and we included 2420 for further analysis. 1764 (72·9%) of 2420 pregnancies were affected by D-antibodies. 95 (3·9%) of 2420 pregnancies resulted in fetal death. Of the 2325 liveborn neonates, 1349 (58·1%) received any form of antenatal treatment and 976 (41·9%) were only treated postnatally. Median gestational age at referral was 20·4 weeks (IQR 14·9-28·0) and ranged between medians of 10·0 and 26·3 weeks between centres. Severe hydrops at first intrauterine transfusion was present in 185 (14·5%) of 1276 pregnancies, with proportions ranging between 0 and 42% between centres. A median of two intrauterine transfusions (IQR 1-4) were done per pregnancy. The fetal access sites used in intrauterine transfusions varied widely between centres. Non-lethal complications in intrauterine transfusions by transfusion site occurred at a lower rate in intrahepatic approaches (2·0%, 95% CI 1·1-3·3) than in placental insertion (6·9%, 5·8-8·0) and free loop (13·3%, 8·9-18·9). The use and indication for intravenous immunoglobulin administration varied widely. Neonates with intrauterine transfusion were born at a median gestational age of 35·6 weeks (IQR 34·0-36·7), ranging between medians of 33·2 and 37·3 weeks between centres, while neonates without antenatal treatment were born at a median gestational age of 37·3 (IQR 36·3-38·1), ranging between medians of 34·9 and 38·9 weeks between centres.

Interpretation: We found considerable variation in antenatal management and outcomes in haemolytic disease of the fetus and newborn between sites in different countries. Our study shows the capacity of the field to gather valuable data on a rare disease and to optimise care.

Funding: None.