African-American women with the sickle cell trait are less likely to delivery prematurely but more likely to have multiple births

Will Boggs:

Women of African-American descent should therefore be offered special screening for blood disorders during pregnancy because "there are clear implications for genetic counseling and screening for urinary tract infections" if the sickle cell trait is detected, Dr. Allison S. Bryant told Reuters Health.

Because of the increased risk of multiple births, she added, physicians should know if a woman is a sickle cell carrier, because early detection of multiple pregnancies is important to ensure good outcomes.

Bryant, from the University of California, San Francisco, and colleagues conducted a study with more than 5,000 African-American women who delivered between 1976 and 2001. Of this group, 6.5 percent carried the sickle cell trait.

Compared with the women without the sickle cell trait, women with the trait were 85 percent less likely to deliver before 32 weeks and 94 percent more likely to be carrying more than one fetus. These relationships were still seen after the effects of assisted reproductive technologies and other influential factors were considered, the report indicates.

The risk of preterm delivery was even lower among women carrying more than one fetus.

There have been other reports of an association between the sickle cell trait and more pregnancies and more live births, Bryant noted.

The sickle cell trait is known to provide a survival advantage in areas were malaria is common, such as Africa. This is because malarial parasite, transmitted to humans by the bite of an infected mosquito, attacks red blood cells, which are less likely to be infected when they have a sickle shape.

Some authors have attributed the features of these pregnancies to the genetic selection of the sickle cell trait -- even in areas where malaria is not a threat. The findings of the current study "may fit into this framework," the researcher concluded.

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