Snoring that begins during pregnancy may be a sign of breathing problems that put women at risk for high blood pressure, a potentially serious complication for the mother and baby, a new study says.
In the study, women who began snoring while pregnant were twice as likely to have pregnancy-induced high blood pressure, or preeclampsia, compared with pregnant women who did not snore.
The findings held even after the researchers took into account factors that could affect blood pressure, such as the mother's age, race, smoking habits and weight gain in pregnancy.
High blood pressure in pregnancy is linked with an increased risk of premature birth and smaller babies.
The study found only an association, and not a direct cause-effect link.
But if breathing problems during sleep do in fact increase blood pressure in pregnant women, the researchers estimate close to 19 percent of pregnancy-related high blood pressure cases, and 11 percent of preeclampsia cases, could be helped by treating snoring.
The new findings suggest that screening pregnant women could help identify those at risk for hypertensive disorders, said study researcher Louise O'Brien, an associate professor at the University of Michigan's Sleep Disorders Center.
A study published earlier this month found that babies born to women with sleep apnea were at increased risk for admission to the neonatal intensive care unit.
"If sleep apnea really is playing a role in these outcomes, then this is a clear opportunity that we can intervene and hopefully improve some of those pregnancy outcomes," O'Brien said.
Snoring and pregnancy
Pregnancy, in fact any weight gain, is known to put people at risk for breathing problems during sleep, including snoring, the researchers said. Earlier studies have also linked breathing problems in sleep to an increased risk of high blood pressure in the general population.
In the new study, O'Brien and colleagues analyzed information from more than 1,700 pregnant women who were at least 28 weeks pregnant. Participants reported whether they snored or gasped for air during sleep, and when the breathing problems began.
Thirty-four percent of women reported snoring as frequently as three to four times a week, and 25 percent said their snoring started during pregnancy.
Among those whose snoring began during pregnancy, about 10 percent had pregnancy-related hypertension, compared with 4.5 percent of those who did not snore.
In addition, 13 percent of those whose snoring began during pregnancy had preeclampsia, compared with 8 percent of those who did not snore.
The researchers noted that the women reported their own snoring, which may not be entirely accurate.
Does snoring cause high blood pressure?
Any pause or obstruction in breathing during sleep increases the activity of the nervous system, which in turn increases blood pressure, O'Brien said.
Breathing problems in sleep are also associated with increased inflammation, which is thought to play an important role in preeclampsia.
It's not known whether the women in the study who began snoring while pregnant also started having high blood pressure at the same time, O'Brien said.
In some sense, the new findings are the opposite of what one would expect — women who were snoring for a short time had a higher risk of high blood pressure than chronic snorers, O'Brien said. But it could be that chronic snorers have adapted to the condition, whereas women who start snoring during pregnancy experience a rise in blood pressure because snoring presents an extra challenge to their bodies, O'Brien said.
O'Brien and colleagues are now conducting a study to see if treating breathing problems with continuous positive airway pressure (CPAP) reduces high blood pressure in pregnant women.
The new study was published online Sept. 10 in the American Journal of Obstetrics and Gynecology. Preliminary results from the study were presented in 2009 at the Associated Professional Sleep Societies in Seattle.
Pass it on: Women who start snoring while pregnant may be at increased risk for high blood pressure.