PEOPLE snore because the flow of air through their mouths and noses is physically obstructed for many reasons. These may include allergies, sinus infections, and nasal polyps. More commonly, snoring is associated with the muscles of the tongue and throat becoming relaxed due to deep sleep, consumption of alcohol, or sleeping pills. But should one be anxious about excessive snoring? Indeed, especially if you are a pregnant woman.

Snoring in women can be a sign of pregnancy-induced hypertension and a risk for growth retardation of the foetus, according to a study reported in CHEST, the journal of the American College of Chest Physicians. Hypertensive disorders during pregnancy are a leading cause of maternal death in the United States and Great Britain, and are important causes of neonatal morbidity and mortality. The cause of these disorders remains unknown.

Because snoring is common in pregnancy, investigators in Sweden studied more than 500 pregnant women to see what effect snoring had on their health. According to Karl Franklin, MD, and colleagues at Umea University Hospital in Sweden, no one had previously investigated whether snoring was associated with hypertensive disorders of pregnancy. Snoring is a sign of increased upper airway resistance and obstructive sleep apnoea (temporary pause in breathing), and is known to be associated with arterial hypertension and coronary artery disease.

Researchers investigated the snoring-related occurrence of pre-eclampsia, a toxaemia of pregnancy characterised by hypertension, proteinuria (excessive serum protein), and oedema (a build-up of fluids in body tissues), as well as daytime sleepiness and infant outcomes. The study included a questionnaire that women completed on the day of their delivery with the involvement of their husband or partner.

Twenty-three per cent said their snoring had become habitual during the last week before delivery. Habitual snoring was described as snoring every night or almost every night. Sleep apnoea was observed in 11 per cent of habitual snorers compared with 2 per cent of non-frequent snorers. The habitual snorers also had a more pronounced weight increase during pregnancy. Fourteen per cent of the women who snored habitually had pregnancy-induced hypertension compared with 6 per cent of the non-frequent snorers. Ten per cent of the women who habitually snored met the definition of pre-eclampsia with hypertension and proteinuria compared with 4 per cent of the non-frequent snorers.

Daytime sleepiness increased among all women during pregnancy, and no marked differences were observed between the habitual snorers and non-frequent snorers. Daytime sleepiness started earlier in pregnancy than snoring. Oedema of the face, hands, legs, or feet occurred in 52 per cent of the habitual snorers compared with 30 per cent of the others.

Infants born to mothers who were habitual snorers were more frequently born with lower birth weights. More than 7 per cent of mothers who were habitual snorers delivered an infant with growth retardation at birth compared with 2.6 per cent among non-habitual snorers. After adjusting for weight, age, and smoking habits, snoring remained a significant predictor of growth retardation. In addition to snoring, smoking was also found to be an independent predictor of growth retardation.

Women who snored habitually and had pre-eclampsia started to snore before any sign of hypertension or proteinuria was present. Habitual snoring was related to sleep apnoea, suggesting that nocturnal upper airway obstruction may contribute to the development of pregnancy-induced hypertension and pre-eclampsia.

Though dentists can identify and treat patients with obstructive sleep apnoea, studies may not have much impact on a typical daily practice, as many women avoid dental treatment during pregnancy or do not comprehend the relationship between dental care and sleep apnoea.