Health experts generally consider the national obesity epidemic as one of the major reasons why incidents of pregnancy-induced diabetes and hypertension (high blood pressure) may be on the rise, but could sleep apnea also be a factor? A study presented last month at the American Thoracic Society 2007 International Conference in San Francisco found that even when controlling for obesity, sleep apnea in the mother increased the risk that diabetes and/or hypertension would develop during the pregnancy.

Obviously, stopping breathing over and over again during the night is not good for anyone, least of all pregnant women, but the study shed light on just how bad this may be for the mother. When the women’s weight was taken into account, sleep apnea was associated with a doubling of the incidence of gestational diabetes and a fourfold increase in the risk of pregnancy-induced hypertension, which includes eclampsia and preeclampsia. According to the Preeclampsia Foundation, eclampsia and preeclampsia are responsible for several hundred women’s deaths and more than a thousand fetal deaths annually in the United States.

The researchers analyzed 2003 data from all pregnancies nationwide associated with sleep apnea, gestational diabetes, and pregnancy-induced high blood pressure. Out of almost 4 million deliveries, 452 had sleep apnea. Of the 167,227 women who had gestational diabetes, 67 had sleep apnea. Of the 200,902 pregnancies with pregnancy-induced high blood pressure, 166 had sleep apnea.

“The repetitive decrease in oxygen that occurs during the night in someone with sleep apnea heightens the body’s ‘fight or flight’ state, which can raise blood pressure,” explained researcher Hatim Youssef, DO, of UMDNJ-Robert Wood Johnson Medical School in New Brunswick, NJ. “The body also secretes more hormones such as cortisol and epinephrine, and the body responds by producing more glucose coupled with a decreased sensitivity to insulin, which can lead to diabetes.”

The weight gain associated with pregnancy can, like any weight gain, worsen sleep apnea, especially during the last trimester when a woman is at her greatest weight. However, it is not just the mother’s health that concerns Youssef. Having the mother’s blood oxygen level dip repeatedly during the night also is likely stressful for the fetus, although researchers do not yet know how or to what extent. “When a mother’s oxygen level drops at night, it may also affect the oxygen level of the fetus, and we don’t know what the long-term effects are,” he said. “That’s why it’s important for a pregnant woman with sleep apnea to be treated with CPAP during her pregnancy.”

Treating sleep apnea has reduced the risk of diabetes and hypertension in non-pregnant women, so now research is needed to confirm if this is also true for pregnant women. “In the future, we want to follow pregnant women whose sleep apnea is well controlled to see if treatment prevents them from developing these conditions, or makes it less severe,” Youssef said.

In the meantime, Youssef recommends a better safe than sorry approach of evaluating pregnant women who are obese and hypertensive for sleep apnea, and, if they have sleep apnea, using an noninvasive treatment such as CPAP.