Pregnancy outcomes in women with elevated levels of fetal hemoglobin

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.

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.

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.

Pregnancies complicated by maternal HbF levels ≥ 70% are at increased risk of intra-uterine growth restriction or SGA fetuses. Increased antenatal surveillance is suggested.