Daughters of Asian-Indian immigrants tend to give birth to smaller babies
Asian-Indian women born in the United States are more likely than their Mexican-American peers to deliver low birth weight infants, despite having fewer risk factors, say researchers at Lucile Packard Children's Hospital and the medical school. The finding confirms previous research that showed a similar pattern in recent immigrants and suggests that physicians should consider their patients' ethnic backgrounds when planning their care.
"Now we see that the daughters of foreign-born women have similar issues," said Packard Children's neonatologist Ashima Madan, MD, "and that the indicators we have traditionally used to predict pregnancy outcomes—maternal educational level, age and access to early prenatal care, for example—aren't reliable for every population." Madan is the lead author of the study, published in the March issue of the Journal of Pediatrics.
Researchers call the previously identified differences in pregnancy outcomes between Indian and Mexican immigrants the "dual paradox." That's because Mexican women giving birth in the United States are more likely than women from India to have healthy-sized newborns, though they are less likely to have completed high school or initiated prenatal care during the first trimester of their pregnancy. In contrast, Indian immigrants, most of whom have completed college and begun prenatal care early, are more likely to deliver a low birth weight infant.
Madan, associate professor of pediatrics, and her colleagues set out to determine for the first time whether this pattern persisted in the U.S.-born daughters of these immigrants. They surveyed more than 6 million births that occurred in 11 states between 1995 and 2000 to white, foreign and U.S.-born Asian-Indian and Mexican women. In addition to collecting data about the mother's birthplace and ethnic group, the birth records documented maternal age, history of prenatal care, maternal use of alcohol or tobacco, maternal educational level and common complications of pregnancy and labor.
They found that Asian-Indian women were more than twice as likely to have low birth weight infants as were white women. These infants weigh 2,500 grams (about 5.5 pounds) or less at birth, either because they grew poorly in the womb or were born prematurely. They were also more than twice as likely to have babies that were small for their gestational age, regardless of whether they were premature. In other words, a generation in America didn't significantly improve or worsen the outcome for the Asian-Indian infants.
In contrast, although infants of foreign-born Mexican-American women closely mirror white infants in weight, the infants of U.S.-born Mexican-American women didn't fare as well, despite the fact that their mothers were more likely to have completed high school and tended to initiate prenatal care earlier. But even though they were more likely to be premature or smaller than infants of foreign-born Mexican-American mothers, they still weighed more, on average, than the infants of Asian Indians.
"You might ask, 'What's so bad about being small?'" said Madan, noting that the growth curves for this and similar studies are based on white infants. "Is this just normal for Asian Indians? But we're concerned because abnormally small babies run a higher risk of fetal distress and often require more intensive medical care and longer hospital stays after birth."
Unusually small babies are also known to be at higher risk for medical problems in adulthood such as diabetes, hypertension and heart disease—conditions that some studies have reported to be higher in Asian Indians.
Madan speculated that maternal birth weight, stress, attitudes toward pregnancy, family support or other risk factors may play a role in fetal growth. In addition, Indian mothers were more likely than either Mexican Americans or whites to have diabetes, which in severe cases can restrict fetal growth.
"Our findings point out how much more we have to learn about fetal growth and well-being," said Madan. "By continuing to study these populations we may identify new interventions that improve perinatal outcomes for women of all ethnic backgrounds."
The paper's senior author is Jeff Gould, MD, professor of pediatrics. Other researchers from the Stanford Prevention Research Center include instructor Latha Palaniappan, MD; research associate Guido Urizar, PhD; Yan Wang, and Stephen Fortmann, MD, professor of medicine.