Normal pregnancy, daytime sleeping, snoring and blood pressure

Abstract

Objective: Investigation of daytime sleepiness, blood pressure changes and presence of sleep disordered breathing, in healthy young women during pregnancy.

Methods: Young, healthy pregnant women between 18 and 32 years of age, seen in three different prenatal care clinics, were enlisted in a prospective study divided in two parts: part 1 of the study consisted of completing a standardized questionnaire on past and present sleep disorders. It also included filling out visual analog scales (VAS) for daytime sleepiness and snoring by the subject and bed partner. Blood pressure measurement was performed at 9 AM as per the WHO protocol. Similar data were collected again at the 6-month prenatal visit and at the 3-month post-delivery visit. At the 6-month visit, ambulatory monitoring of nocturnal sleep using a portable six-channel recorder (Edentrace^®) was performed at home. Part 2 involved a subgroup of subjects that were randomly selected after stratification based on results of VAS and ambulatory monitoring. It included 1 night of nocturnal polysomnography with esophageal manometry and 24 h of ambulatory BP monitoring with portable equipment with cuff inflation every 30 min.

Results: Of the 267 women who participated in part 1 of the study , only 128 consented to enroll in part 2, from which 26 were selected to undergo polysomnography. At the 6-week prenatal visit 37.45% of the subjects reported daytime sleepiness of variable severity. At the 6-month visit, this was noted in 52% of the subjects. Bed-partners reported chronic, loud snoring prior to pregnancy in 3.7% of the study population, but this increased to 11.8% at the 6-month visit. Blood pressure (BP) remained below the pathological range, i.e. less than 150/95 mm Hg, during the entire pregnancy. However, ambulatory monitoring indicated that 37 women, including the loud chronic snorers, had some minor SaO₂ drops during sleep and this same group presented the largest increase in BP between the 6th week and the 6th month prenatal visits. Part 2 included 26 women, 13 from the above identified 37 women and 13 from the rest of the group, chosen randomly, age and body mass index (BMI) matched. Polysomnography did identify two abnormal breathing patterns during sleep: (1) esophageal pressure ‘crescendos’ associated predominantly with stage 1 and 2 NREM sleep, and (2) ‘abnormal sustained efforts’ seen predominantly with delta sleep. These abnormal breathing patterns were noted during a significantly longer time during sleep. This group of women with the abnormal breathing patterns were not only chronic snorers but also had significantly higher systolic and diastolic BP increases when compared to the 13 other non-snorers. Six out of the 13 snorers were ‘non-dippers’ at the 24-h BP recording.

Conclusion: Abnormal breathing during sleep (that is frequently, but not always, associated with loud, chronic snoring, and may be a consequence of edema induced by hormonal changes associated with pregnancy), can be seen in otherwise healthy young pregnant women. It may contribute to the symptom of daytime sleepiness. The changes in blood pressure noted were of no pathological significance in our population but could be an added risk factor in high-risk pregnancies.

Introduction

Chronic snoring has been considered to be a marker of sleep disordered breathing in many studies of sleep pathology. In 1996 Loube et al. [1] indicated that snoring increases during pregnancy, however, preliminary data obtained in the early 1980s on a small number of pregnant women, using calibrated induction respiratory plethysmography, had not identified the presence of significant obstructive sleep apneas. The current prospective study aimed to evaluate the severity of snoring as scored by the bed-partner at two different times (6 weeks and 6 months) during normal pregnancy. The second objective was to evaluate the potential association of oxygen saturation drops with changes in blood pressure during pregnancy in the chronic snorers as opposed to non-snoring pregnant women using an ambulatory blood pressure monitor. Finally, we also aimed to investigate the presence of any abnormal respiratory pattern during sleep in a sub-sample of the population who had chronic snoring, and to study the shape of the 24-h blood pressure curve in this group.

The crucial question that needed to be answered was ‘should we pay more attention to chronic snoring during pregnancy due to its common association with sleep disordered breathing?’