Snoring in Pregnancy May Affect Mother's Blood Pressure and Baby's Size

Jan. 4, 2000 (New York) -- Women who begin to snore habitually during pregnancy may be at an increased risk for high blood pressure and of delivering smaller babies, according to Swedish researchers.

In a study appearing in the January issue of Chest, habitual snorers had a higher incidence of high blood pressure, preeclampsia, abnormal accumulation of fluid in the tissues, and weight gain. The women's infants were smaller and had lower scores of physical condition than did the infants of mothers who snored infrequently during pregnancy.

High blood pressure and preeclampsia, a condition associated with pregnancy that involves high blood pressure, protein in the urine and fluid retention, developed in more than twice as many snorers as nonsnorers, report Karl A. Franklin, MD, PhD, and colleagues from Umea University Hospital. The authors say that previous studies have shown an association between pregnancy and increased snoring frequency, but that their study is one of the first to suggest a connection to high blood pressure as well an adverse effect of the mother's snoring on the infant.

The study included 502 women and their partners who were questioned on the day they gave birth about incidence of snoring, witnessed sleep apnea (stopping of breathing for short periods during sleep) or disruption in breathing during sleep, and daytime fatigue as well as smoking habits, medication use, and whether they had any medical problems or diseases.

Overall, 24% of women reported that they had begun snoring or increased their snoring by the third trimester, and 23% said their snoring was habitual in the week before delivery. Of these women, 10% met the definition of preeclampsia with high blood pressure and protein in the urine compared with 4% of infrequent snorers.

Fourteen percent of snorers met the definition for pregnancy-induced high blood pressure compared with 6% of infrequent snorers. Women who reported habitual snoring weighed more prior to pregnancy and gained more weight during pregnancy than infrequent snorers. They also experienced more fluid retention.

Among the infants, 7% of those whose mothers were habitual snorers were considered small for gestational age at birth compared with 2.6% of those whose mothers did not snore habitually. Apgar scores, which are a measure of an infant's physical health immediately after birth, were lower than average in 12.4% of infants of snoring mothers compared with 3.6% of infrequent snoring mothers. Witnessed sleep apnea, though higher in snorers than infrequent snorers (11% vs. 2%), was not associated with adverse outcomes in the infant.

According to Franklin and colleagues, the findings indicate "that the consequences of increased upper airway resistance during sleep may affect the fetus and supports the previously suggested relationship between sleep apnea and intrauterine growth retardation." Babies with intrauterine growth retardation have delayed development and are smaller than average.

The authors say that all the women in their study who were habitual snorers reported that snoring started prior to any sign of high blood pressure or protein in the urine. The researchers conclude that obstruction of the airways during the night is a likely contributor to the development of high blood pressure and preeclampsia in pregnancy, although the exact mechanisms by which snoring could contribute to high blood pressure are unknown.

But a sleep expert who has conducted similar research tells WebMD that while the findings are intriguing, there is little evidence in the general population that snoring alone is associated with any health risks. "Snoring as an indicator of sleep-disordered breathing ... is a different story. That has been noted to be associated in a number of studies with [high blood pressure]," says Daniel Loube, MD. "The frequency of sleep-disordered breathing in a population of pregnant women is going to be relatively low, and to say that snoring by itself is a cause of intrauterine growth retardation is a very long reach."

Loube, who is the director of the Sleep Disorders Center at the Virginia Mason Medical Center in Seattle, says that the use of questionnaires rather than clinical sleep studies that could differentiate snoring from sleep-disordered breathing makes it difficult to put much weight into a connection between snoring in the mother and growth retardation in the fetus.

Loube says about one-third to one-half of pregnant women snore, largely as a result of increasing fluid retention in the nasal passages as pregnancy progresses.