Asian and Hispanic women may have a heightened risk of developing pregnancy-related or “gestational” diabetes - and so may women with partners of those same backgrounds, a new study finds.

Researchers found that among nearly 140,000 women in one large California health plan, Asian women had the highest rate of gestational diabetes, at nearly 7 percent. They were followed by Native American women, at 5.6 percent, and Latina women, at 5 percent.

Rates of gestational diabetes among white and black women, meanwhile, stood between 3 and 4 percent.

But it wasn’t only women’s race and ethnicity that mattered, the study found. Expectant fathers’ backgrounds also showed an independent association with the risk of gestational diabetes.

When the father was Asian or Hispanic, the researchers found, a woman’s risk of gestational diabetes was 41 percent and 29 percent higher, respectively, compared with when the father was white. That was with other factors - including the mother’s race and ethnicity, age, body weight and education - taken into account.

Native American ethnicity was also linked to relatively higher risks, though the association was weakened when other factors were considered.

Estimated to affect between 3 percent and 8 percent of pregnant women in the U.S., gestational diabetes arises during pregnancy and goes away soon after childbirth, though women who develop it have a higher-than-average risk of eventually developing type 2 diabetes.

Gestational diabetes can raise the risk of certain pregnancy complications, like high blood pressure in the mother and having a larger-than-normal baby, which may require a C-section.

Studies have shown that in the U.S., minorities generally have a higher risk of gestational diabetes than white women do.

These latest findings, published in the American Journal of Obstetrics & Gynecology, confirm a role for women’s race and ethnicity in gestational diabetes risk.

But they also suggest that “in addition to women who are Asian, Latina, or Native American, women whose partners are of these racial/ethnic groups also appear to be at higher risk for (gestational diabetes),” write Dr. Aaron B. Caughey and his colleagues at the University of California, San Francisco.

The findings may help guide gestational diabetes screening, the researchers note.

For women at average risk of gestational diabetes, doctors typically perform a blood sugar test at some point in the second trimester. Those considered to be at high risk may be screened at their first prenatal visit and then retested later in pregnancy.

It is not clear why certain racial and ethnic groups are at increased risk of gestational diabetes, but genetic predisposition likely plays a role, according to Caughey’s team.

They point out that a number of studies have found increased risks among Asian women, despite the fact that they have relatively low levels of obesity, a risk factor for both gestational and type 2 diabetes.

As for why the father’s race and ethnicity matters, the researchers explain that fathers’ genes, as well as mothers’, influence hormones in the placenta. Placental hormones, in turn, affect a pregnant woman’s sensitivity to the hormone insulin, which regulates blood sugar. Impaired insulin sensitivity can then lead to gestational diabetes.

SOURCE: American Journal of Obstetrics & Gynecology, online April 19, 2010.