Pregnancy outcomes in women with elevated levels of fetal hemoglobin

OBJECTIVE: Elevated maternal levels of fetal hemoglobin (HbF) present a unique situation where both mother and fetus produce hemoglobin with equivalent oxygen affinities. We aimed to determine pregnancy outcomes in women with persistently elevated HbF. METHODS: In this retrospective cohort study, women with HbF levels exceeding 10% were identified by searching a provincial database. Maternal, obstetric, and neonatal outcomes were extracted from chart reviews performed at two hospitals. RESULTS: Twenty-two women with a total of 43 pregnancies and 33 live births were identified. Maternal levels of HbF ranged between 11 and 100%. Women with HbF ≥ 70% were significantly more likely to deliver growth-restricted or small for gestational age (SGA) fetuses compared to the group of women with HbF < 70% (100% versus 8%; p < 0.01). Three women (4/32 pregnancies) received blood transfusions, which was unrelated to HbF levels. CONCLUSIONS: Pregnancies complicated by maternal HbF levels ≥ 70% are at increased risk of intra-uterine growth restriction or SGA fetuses. Increased antenatal surveillance is suggested.