Introduction
High blood pressure disorders are one of the most important and controversial unresolved issues in obstetrics. This complication is one of the causes of maternal death and disability in mothers and babies, and every year more than 4 million women in the world face this problem [1, 2]. Sleep disorder is one of the most common problems during pregnancy and 79% of pregnant women in the world suffer from a sleep disorder [10]. Sleep disorders are associated with oxidative stress and endothelial dysfunction. In addition, they can increase adrenal hormones and cortisol, activate sympathetic nerves, and increase tumor necrosis factor-alpha, and these factors are effective in increasing blood pressure [11]. Considering the prevalence and importance of sleep disorders in pregnancy and the conflicting results regarding the relationship between sleep disorders and preeclampsia, this study was conducted to determine the relationship between sleep disorders and preeclampsia.

Materials and Methods
This research was a case-control analytical study that was conducted in 2017 on 240 women who were referred to the affiliated university hospitals of Mashhad (Imam Reza, Qhaem, Umm Al-Banin, and Hasheminejad). After obtaining the Ethics Committee’s approval from the Mashhad Nursing and Midwifery School and obtaining other necessary permissions, data collection began. The inclusion criteria included Iranian nationality, gestational age of 28 to 40 weeks, no speech, hearing, or mental problems, no stressful experience in the previous 6 months, pre-eclampsia in the case group, and no pre-eclampsia in the control group. The exclusion criterion during the study included the unwillingness to continue participating in the study.
Preeclampsia was diagnosed based on blood pressure equal to or greater than 140/90 along with proteinuria of more than 300 mg in 24-hour urine or equal to or greater than 1 plus in strip test. This information was obtained by studying the clinical file and blood pressure measurement by the researcher and confirmed by the gynecologist. The control group (healthy group) was selected from pregnant women without preeclampsia referring to the midwifery clinic for prenatal care and maternity wards of the mentioned hospitals. The data collection tool included a demographic information questionnaire containing gynecology/obstetrics records, a Pittsburgh sleep quality questionnaire, and a clinical evaluation form to determine the symptoms and severity of preeclampsia, which was completed by the researcher for each person in the case and control groups.

Results
The average age of the mothers in the control group (healthy group) was 29.0±6.5 and in the case group (preeclampsia group) was 31.5±0.7 years, and based on the Mann-Whitney test, a statistically significant difference was observed between the two groups (P=0.008) (Table 1).



The actual sleep at night was 8.4±2.3 hours in the healthy group and 8.0±2.2 hours in the case group, and a statistically significant difference was observed between the two groups (P=0.028). In terms of loud snoring, waking up in the middle of the night was the most frequent in the case group, and there was a statistically significant difference between the two groups according to the Mann-Whitney test (P<0.001). There was a statistically significant difference between the two groups in terms of sleep quality scores (P<0.001) so that 27.8% of people in the preeclampsia group had serious sleep problems compared to 6% of people in the healthy group (Table 3).



Based on the logistic regression test, removing the effect of age, body mass index, and gestational age, the risk of preeclampsia in women with a history of waking up in the middle of the night or early morning once a week was 7.03 times that of women without a history of waking up in the middle of the night (P<0.001), and the risk of preeclampsia in women with a history of loud snoring twice a week was 9.45 compared to women without a history (P<0.001). The risk of preeclampsia in women with serious sleep problems was 11.11 times that of women in the control group (P<0.001). Also, the risk of preeclampsia in women with a history of waking up three times due to extreme heat per week was 2.40 times compared to healthy women (P=0.029).

Discussion
In the present study, the highest frequency of loud snoring (38.8) was observed in the group of women with preeclampsia. In the case-control study by Kordi et al. (2015), which was conducted on 150 pregnant women with preeclampsia and 150 non-affected pregnant women, there was a significant relationship between sleep quality and preeclampsia (P<0.001), which is consistent with the results of the present study [12].
Kesby et al. (2000) in a study on 25 patients with preeclampsia and 17 non-affected women found that sleep disorders were more common in affected women (P<0.001) [19]. In the study by Ekholm et al. (1992), the average number of nocturnal body movements was significantly higher in the group with preeclampsia (P<0.005) [20]. In the current study, 27.8% of people in the group of women with preeclampsia had serious sleep problems, which was 6% in the control group so that women with preeclampsia had poor sleep quality.
Gottlieb et al. (2006) in a cross-sectional study on men and women aged 100-40 years stated that people who sleep less than 6 hours a night have a higher average blood pressure compared to people who sleep 7-8 hours a night [24]. In the present study, 66% of women with preeclampsia had less than 5 hours of sleep, which is in line with other studies. The present study showed that sleep disorders in pregnancy are associated with an increased risk of preeclampsia and it is necessary to pay attention to the recognition and planning to control and treat sleep problems in pregnant women. Therefore, it is suggested that midwives, doctors, and other medical groups pay more attention to the pattern and quality of people’s sleep in pre-pregnancy and pregnancy care, and assist by teaching self-care measures and early diagnostic and consider treatment measures in order to improve sleep quality and prevent the occurrence of subsequent disorders, such as pre-eclampsia.

Ethical Considerations

Compliance with ethical guidelines
The present paper is the result of a research project approved by the Vice-Chancellor for Research of Mashhad University of Medical Sciences (Code: IR.MUMS.NURSE.REC.1397.042).

Funding
This study was funded by the Mashhad University of Medical Sciences.

Authors' contributions
All authors equally contributed to preparing this article.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
Authors appreciate the Deputy of Research, Mashhad University of Medical Sciences for financial support.

 

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