Outcomes of pregnancies complicated by haemoglobin H-constant spring and deletional haemoglobin H disease: A retrospective cohort study.

The objective of the study was to compare the maternal and foetal outcomes of pregnancies complicated by Hb H-constant spring (HbH-CS) disease/deletional HbH (HbH-del) disease and low-risk pregnancies. A retrospective cohort research was undertaken on singleton pregnancies with Hb H-CS and Hb H-del diseases. The controls were randomly selected with a control-to-case ratio of 10:1. A total of 55 cases of HbH-CS disease, 231 cases of HbH-del disease and 2860 controls were compared. The mean gestational age at delivery and birthweight were significantly lower in the HbH-CS group than in the HbH-del and control groups. The clinical course of Hb H-CS was more severe than that of HbH-del disease. The rates of preterm birth, foetal growth restriction and low birthweight were significantly increased in the HbH-CS and Hb H-del groups. These rates were significantly greater in the HbH-CS group than in the H-del group. The maternal outcomes were not significantly different among the three groups. In conclusion, pregnancy worsens the course of HbH disease, more noticeably in HbH-CS disease. Hb H disease significantly increases the risk of adverse foetal outcomes, more noticeably in the HbH-CS group. Pregnancy is relatively safe for women with HbH disease.