A Canadian population-based observational cohort study of alpha and beta-thalassemia syndromes in pregnancy

Beta-thalassemia can adversely affect pregnancy, but the impact of alpha-thalassemia is less studied. We assessed whether patients with symptomatic alpha-thalassemia have similar pregnancy outcomes as patients with symptomatic beta-thalassemia.

We conducted a population-based retrospective cohort study of 1,324,488 pregnancies in Quebec, Canada, between 2006 and 2022. The exposures were maternal symptomatic alpha-thalassemia, symptomatic beta-thalassemia, thalassemia trait, and other thalassemia syndromes. Primary outcomes were severe maternal morbidity, preterm birth, preeclampsia, and other pregnancy complications. We used log-binomial regression models to estimate adjusted risk ratios (RR) and 95% confidence intervals (CI) for the association between each thalassemia and adverse pregnancy outcomes.

In total, 825 patients had symptomatic alpha-thalassemia, 681 symptomatic beta-thalassemia, 1,749 thalassemia trait, and 2,377 other thalassemia syndromes. Compared with no thalassemia, alpha-thalassemia (RR 3.05; 95% CI: 2.36-3.94) and beta-thalassemia (RR 2.52; 95% CI: 1.84-3.45) were associated with a greater risk of severe maternal morbidity. However, alpha-thalassemia was additionally associated with preterm birth (RR 1.45; 95% CI: 1.16-1.82), preeclampsia (RR 1.67; 95% CI: 1.27-2.20), and gestational diabetes (RR 1.79; 95% CI: 1.52-2.09). Beta-thalassemia was not associated with these outcomes, and associations were weak for thalassemia trait and other thalassemias.

The findings suggest that symptomatic alpha-thalassemia is associated with a wider range of pregnancy complications than symptomatic beta-thalassemia and other thalassemia syndromes. However, symptomatic alpha and beta-thalassemia are both associated with severe maternal morbidity.