Boy/Girl Imbalance in Children Born to Asian-Born US Mothers

April 17, 2012 (Phoenix, Arizona) — An imbalance in the ratio of girls to boys born to mothers in the United States who were born in China and India suggests patterns similar to those associated with some Asian cultures, according to a study presented here at the American Institute of Ultrasound in Medicine 2012 Annual Convention.
When Asian mothers living in Santa Clara County in California were evaluated according to their country of birth, notable differences in the ratios of male and female children were found between mothers born in China and India, which are associated with cultural biases toward boys, and those born in Pakistan, which has no such association, explained lead author G. Sharat Lin, PhD, from Advanced Imaging Associates in Fremont, California.
The California Department of Public Health database provided annual birth statistics from 1995 to 2009. The statistics reflect data according to county, race, and the sex of the child. Statistics reflecting the country of birth of the mother were obtained from the Santa Clara County Public Health Department.
Among mothers born in China, the sex ratio, defined as the number of females born for every 1000 males, ranged from a low of 784 in 1996 (n = 528) to a high of 1040 in 2007 (n = 1177) and 2008 (n = 1083). From 1995 to 2009, the cumulative sex ratio was 931.
For mothers born in India, the sex ratio ranged from 803 in 1995 (n = 779) to 1006 in 1998 (n = 1338), with a cumulative ratio for the study period of 937.
In comparison, the sex ratios for mothers born in Pakistan ranged from 747 in 2001 (n = 145) to 1279 in 1998 (n = 98), with a cumulative ratio of 992.
For all Asians mothers in Santa Clara County, the ratios ranged from 902 to 965 over the study years (mean, 936).
Comparatively, sex ratios in the general American population ranged from 937 to 962, with a cumulative sex ratio for the study period of 951.
The findings underscore a trend toward lower sex ratios in the cultural groups most associated with sex-selective abortions in their countries of origin, Dr. Lin told Medscape Medical News.
"The significance of this study is that low [sex] ratios in Asians in California is confirmed by [sex] ratios in specific ethnic groups and not others," he said.
"The low [sex] ratios are not entirely statistical fluctuations, but are correlated with cultural preferences," he explained.
In a previous study, Dr. Lin and colleagues evaluated the role of the proliferation of "keepsake" 4D ultrasound businesses promoting sex identification in sex ratio imbalances; however, the research fell short of proving any kind of causative association.
Factors that clearly could influence such preferences include deep-seated traditions from previous generations, Dr. Lin added.
"Broadly speaking, sex preference is cultural. For example, Hindu marriages in the United States continue to practice dowry, even if of a lesser magnitude and less mandatory, from the bride's family to the groom's family. This is an example of a culturally based financial incentive to have boys," he explained.
"In most Indian and Chinese families, the patrilineal society favors boys to carry on the family line."
China's well-documented sex imbalance, driven largely by the country's 1-child policy, is reportedly improving. The official newspaper, the People's Daily, reported in March that 117.78 boys were born to every 100 girls in China in 2010, down from 119.45 in 2010 and 117.94 in 2009.
In India, however, the imbalance is said to be worsening because of a long-held perception of males as financial providers. Census data showed a sex ratio of 914 in 2011, a steep decline from the ratio of 933 in 2001, according to a Reuters report.
The extent to which cultural biases influence birth rates in the United States is not clear, but with imbalances still so prevalent in other countries and with the number of immigrants to the United States, it is an issue, said David N. Jackson, MD, professor of obstetrics and gynecology in the division of maternal–fetal medicine at the University of Nevada School of Medicine in Las Vegas, who moderated the session.
"This is a provocative observational report that raises the question of [sex] selection as an ongoing issue in pregnancies in the United States," said Dr. Jackson.
He noted that the issue of keepsake ultrasound is "interesting and provocative," but that much more research is needed to confirm any kind of association with sex ratios.
"It's very speculative but probably deserves further scientific confirmation," he said.
The US Food and Drug Administration has issued public statements about the keepsake ultrasound businesses, discouraging the use of ultrasound unless it is medically necessary.
Although the warnings do not address the issue of sex identification, the agency cautions that the long-term effects of repeated ultrasound exposure on the fetus are not fully known, and that ultrasound imaging done by technicians with inadequate training could potentially result in longer exposure times and higher energy levels than are usually used in medical situations.
The businesses are not prohibited, but Dr. Lin said they seem to be shifting to lower-profile locations.
"They appear to be increasing in number in outlying suburban areas where they feel they will be subject to less regulatory scrutiny," he said. "There are fewer such businesses in large cities and in their urban cores."
Dr. Lin and Dr. Jackson have disclosed no relevant financial relationships.
American Institute of Ultrasound in Medicine (AIUM) 2012 Annual Convention: Abstract 1241752. Presented March 31, 2012.

Authors and Disclosures


Nancy A Melville

Nancy Melville is a freelance writer for Medscape.

Disclosure: Nancy Melville has disclosed no relevant financial relationships.

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