(CNN) - If you're pregnant and you (or your other half) notice you've started to snore, you might want to talk to your doctor. You could be at greater risk of getting high blood pressure and preeclampsia, according to a new study in the American Journal of Obstetrics and Gynecology.
Preeclampsia, left untreated, can be life-threatening to the mother and unborn child. It usually starts after the fifth month of pregnancy and causes a pregnant woman's blood pressure to go up and the presence of protein in the mother's urine. This can significantly affect the placenta and the mother's liver, kidney and brain.
Preeclampsia can cause seizures and is the second leading cause of death in pregnant women in the United States. It's also a leading cause of fetal complications including premature birth, low birth weight and stillbirth. There is no cure short of delivering the baby.
The study, conducted by the University of Michigan, was the largest of its kind and the first to show that women who begin snoring after they become pregnant have a greater risk of getting high blood pressure and face significant risk to their cardiovascular health, says lead author Louise O'Brien, an associate professor at the University of Michigan's Sleep Disorders Center.
"What we found was that snoring during pregnancy was indeed strongly associated with gestational hypertension and preeclampsia," O'Brien told CNN. "That was after we had accounted for other known risk factors. What was a novelty about this study was that we looked at women who have been snoring before they got pregnant and women who developed snoring during their pregnancy. It was actually the women who started snoring after they became pregnant that were at highest risk of high blood pressure problems."
More than 1,700 pregnant women participated in the study. They were recruited in their last trimester - 28 weeks and up. O'Brien says 25% of them started snoring frequently once pregnant, doubling their risk of high blood pressure compared to women who don't snore. Nine percent reported chronic snoring.
Chronic snoring - snoring three to four nights a week - is an indication of a sleep disorder. O'Brien says these women can be treated for "sleep disordered breathing" by using a continuous positive airway pressure machine, or CPAP. The machine is worn during sleep and pushes out mild air pressure to help keep the person's airways open.
O'Brien has a new study underway to determine whether using a CPAP decreases hypertension in pregnant women. But she says while more than one-third of these pregnant women were snoring by their last trimester, not all of them will have sleep apnea. There are a number of things pregnant women can and should do.
'Women should mention frequent snoring to their doctor," O'Brien said. "The problem is many women don't mention sleep problems to their obstetrician and conversely obstetricians don't ask their patients about sleep problems either."
O'Brien reminds expectant mothers that how you sleep is also important. Snoring is much more common when people lay on their back, which most pregnant women don't do. For pregnant women, side sleeping is better - preferably the left side, she says, because the weight of the uterus presses down on some of the vessels that bring the blood back to the lungs.
Her message for physicians? "If they have a patient who has gestational hypertension or preeclampsia and they ask them if they snore frequently and the answer is yes, those are the patients who may benefit from a more thorough sleep apnea workup."
The takeaway of this study is simple, says O'Brien: "If we can highlight the importance of snoring in pregnant women and we can encourage obstetricians to ask their patients about snoring, it is important not just to ask at the initial visit but also continue to ask as the pregnancy progresses. I think this study also reinforces the fact that we need to look at treatment intervention trials to see if we can improve maternal hypertension by treating any underlying sleep apnea."