Pregnancy outcome of hemoglobin H disease

Abstract

Hemoglobin H (Hb H) disease is one of the major thalassemic diseases, and it predominantly affects Southeast Asia, the Middle East, Greece, and Cyprus [1]. The loss of 3 α-genes results in a severe imbalance in the production of globin chains, and the globins produced in excess form Hb H, an unstable hemoglobin with a high oxygen affinity [2]. The clinical manifestations of Hb H disease vary from no clinical symptoms to severe chronic hemolytic anemia. The physiologic changes during pregnancy increase the severity of anemia in the mother, which could affect pregnancy outcome as well as clinical symptoms [3]. There has been no large-series report on this disease in pregnant women. Of nearly 40,000 pregnant women attending the antenatal clinic of Ramathibodi Hospital in Bangkok, Thailand, from 1997 to 2003, 16 were diagnosed as having Hb H before the pregnancy (group 1) and 111 were diagnosed through the thalassemic screening program; of these, 95 formed group 2. The mean ± maternal age was 27.62 ± 5.29 years; height was 155 ± 5.25 cm, and body mass index (BMI, calculated as weight in kilograms divided by the square of height in meters) was 21.50 ± 3.26. There were 59 nulliparas and 52 multiparas. A total of 94 women were anemic (Hb < 11 g/dL), and the median (range) hemoglobin levels at baseline and in the early third trimester were 8.5 g/dL (5.4–12.1 g/dL) and 8.5 g/dL (4.8–12.3 g/dL), respectively. No women in group 1 were found to have normal hemoglobin levels, and 5 women in this group were given blood transfusions because of clinical symptoms of severe anemia or intrauterine growth restriction. Of the 111 women, 73 had a vaginal delivery and 38 had a cesarean section. The 2 most common indications for a cesarean section were fetal distress (36%) and cephalopelvic disproportion (28%). No serious maternal complications occurred during the study. The mean birth weight was 2920 ± 496 g, but 15.45% of the newborns weighed less than 2500 g at birth. In group 1, 6 newborns (37.5%) had a low birth weight and 4 of the mothers had severe anemia during the first trimester of pregnancy. In group 2, only 12.63% of the newborns had a low birth weight. Preterm deliveries were 3.6% of all deliveries, and all preterm births occurred in group 2. Among the 7 couples at risk, there were 2 cases of hydrops fetalis due to Bart hemoglobin. The pregnancy was terminated in both cases. In conclusion, pregnant women with Hb H disease require special care, as severe anemia may adversely affect their health and the health of their developing fetuses. However, asymptomatic Hb H disease in women had no adverse affect on pregnancy outcomes. The incidence of low birth weight was high among women who were diagnosed with the disease before their pregnancy, especially for those having severe anemia.