Racial Disparity in IMR for Multiple Births

Drs. Barbara Luke of the University of Miami in Coral Gables, Florida, and Morton B. Brown of the University of Michigan, Ann Arbor, compared the most recent decade on record in the US Birth Cohort Linked Birth/Infant Death Data Sets with the previous decade for overall infant mortality rates and the change in mortality risk with multiple births. They also assessed the risks by race.

There were 11,317,895 live births in 1989-1991 and 11,181,095 in 1999-2001. There were 89,823 infant deaths in 1989-1991 and 67,129 in 1999-2001.

Infant mortality risk decreased significantly for singleton, twin and triplet births and decreased nonsignificantly for quadruplet and quintuplet births. The decreases were greater for twins overall and for twins born at less than 37 weeks gestation. For triplets, risk dropped for those born at less than 39 weeks gestation.

The largest reduction in infant mortality risk was for triplets born between 20-24 weeks gestation and quadruplets and quintuplets born between 25-28 weeks gestation.

When the risks were analyzed by race, infant mortality decreased significantly for all singletons, and for twins and triplets born at every gestational age for whites. For blacks, risk dropped for singletons overall, for twins born at less than 37 weeks gestation and for triplets born between 25-28 weeks gestation.

Black infants had a survival advantage at gestational age below 33 weeks than white infants, but survival was significantly lower for black infants at gestation age above 33 weeks gestation than whites.

Drs. Luke and Brown report that "the improved survival of smaller and more immature infants has long-term social, economic and health implications."

Pediatrics 2006;118:2488-2497.