A number of other factors seem to play a role. Mothers younger than 20 years or older than 40 have children with a higher infant mortality. First babies have a higher chance of death than later siblings. Unmarried mothers also have a higher rate of death in their children, more than 70 percent higher than that of married mothers.
The No. 1 cause of infant mortality among newborns is premature birth, which has traditionally been linked with inferior prenatal care. That may not be the case in the United States. A 2006 study published in Epidemiology looked at how preterm delivery occurred among women in active-duty military installations.
Such women receive the same prenatal care regardless of race, or even socio-economic status. Because they were guaranteed care, their overall risk of premature delivery was low, just over 8 percent. But even among these women, black women were more than two times as likely as white women to deliver prematurely, regardless of military rank.
A Cochrane Systematic Review of the additional support women received during at-risk pregnancies included 17 studies and more than 12,000 women. Additional care was not associated with any improvements in any perinatal outcomes. C-sections were less common, as was hospital admission after birth, but infant mortality was not affected.
Another such review examined how the number of prenatal visits affected infant mortality. Seven studies involved more than 60,000 women in countries of varying income. There was no difference in high-income countries in the number of deaths of those who had more or fewer visits (although the number of deaths over all was low). In low- and middle-income countries, perinatal mortality was higher in groups with reduced visits, but the overall difference was small. The authors concluded that in places where the number of visits was already low, reducing the number of visits further was a…