Pregnancy is a special period characterised by hormonal, physical, and psychological changes that can affect sleep, leading to sleep problems or aggravation of existing sleep problems in pregnant women. Increased progesterone levels can lead to fatigue and drowsiness. Night-time gastrocnemius twitches, frequent urination, frequent foetal movements, pain in the lower back or pubic bone, and maternal concerns about foetal development can cause sleep disturbances. Sleep disturbances during pregnancy have an important impact on the health of mother and child. Some studies have reported that sleep disturbances during pregnancy may be associated with pregnancy-induced hypertension syndrome, preterm birth, increased caesarean section rates[21-24], and an increased risk of attention deficit hyperactivity disorder in children[25].
The results of this study demonstrated that patients with DIP were older and had a larger neck circumference and higher preconception weight and preconception BMI than the control group. This finding is consistent with the risk factors for DIP confirmed in previous studies[26, 27]. The PSQI scale survey indicated that the patients with GDM or PGDM had higher overall PSQI scores and scoring grades than the control group. This finding indicated that sleep quality in patients with DIP was poor. The analysis of PSQI scoring items indicated that the patients with DIP had shorter sleep time, less efficient sleep, and more sleep disorders and daytime dysfunction than the control group. Some researchers have proposed the concept of the midpoint of sleep, which is defined as the midpoint moment between the time of falling asleep and the time of waking up; their results revealed that pregnant women with the midpoint moment occurring later in the night (later than 5:00 am) had an increased incidence of GDM (OR = 2.58), which was not associated with age, BMI, ethnicity, and self-perceived frequent snoring[28]. Therefore, the time to fall asleep late also increased the risk of GDM. Our results are consistent with these results. Patients with GDM scored higher in terms of time to fall asleep than the control group; however, the patients with PGDM exhibited no statistically significant differences with the control group. In addition, the analysis of the type of sleep disorders indicated that patients with GDM or PGDM had higher difficulty falling asleep (frequency of not falling asleep within 30 min every week) than the control group. This finding suggested that patients with DIP were less likely to fall asleep sooner than the pregnant women without diabetes.
After analysing the specific types of sleep disorders in patients, it was observed that patients with GDM or PGDM scored higher than the control group in terms of many events that affect sleep. Additionally, the patients with DIP had more sleep disorders. In terms of going to the toilet at night, the patients with DIP scored lower than the control group. Frequent urination may occur due to enlargement of the uterus and compression of the bladder during pregnancy, and the vast majority of normal pregnant women experience frequent urination at night. Patients with DIP face more obvious sleep disorders; therefore frequent urination at night, which is common during pregnancy, was not considered. Analysis of the type of daytime dysfunction in the study participants indicated that the score of the patients with DIP in terms of frequent sleepiness and lack of energy to do things was higher than the control group. Whether there is a correlation between sleep disorders and gestational diabetes remains controversial. A meta-analysis reported that sleeping for too short time increases the risk of GDM[29]. However, another meta-analysis reported the association of prolonged long sleep timing but not of too short sleep timing with the incidence of GDM[30]. Studies during different trimesters have reported that the relationship between sleep duration and the occurrence of GDM in the first trimester is uncertain[31]. A short sleep duration in the second trimester was associated with the development of GDM[32, 33]. Studies from China have reported that poor sleep quality may be associated with high blood glucose or GDM during pregnancy[34]. Sleep quality is more closely associated with an increased risk of GDM than sleep duration[35]. The definition of too long or too short sleep time has been inconsistent in studies. Moreover, different sleep scales have different pertinence and errors, and the study subjects’ responses to the questionnaire are also interfered with by various factors. Therefore, to determine whether sleep is related to DIP, objective indicators such as polysomnography (PSG) are needed. Moreover, future prospective studies with a large sample size are needed.
Excessive weight gain during pregnancy, respiratory mucosal hyperaemia, and oedema can increase the incidence of sleep-disordered breathing[36]. In the present study, the patients with GDM or PGDM exhibited higher overall STOP-BANG scores than the control group. This finding indicated that the patients with DIP have a higher risk of OSAHS than pregnant women without diabetes. In the analysis of STOP-BANG scores, the proportion of patients with GDM or PGDM having fatigue, hypertension, BMI > 35 kg/m2, and neck circumference > 40 cm was higher than that of the non-diabetic pregnant women. Snore and breathing stops were not significantly different between the patients with GDM or PGDM and non-diabetic pregnant women. Although no significant differences were observed in terms of snore and breathing stops between the patients with DIP and the control group, we inferred that the risk of OSAHS is higher in patients with GDM or PGDM due to the effects of fatigue, blood pressure, BMI, and neck circumference. A growing body of research has confirmed that OSAHS is strongly associated with abnormalities in glucose metabolism. OSAHS causes intermittent hypoxemia, sleep deprivation, and hypercapnia at night, which can cause insulin resistance and affect glucose metabolism. Meta-analyses have reported that pregnant women with sleep-disordered breathing were at a high risk of developing GDM. Both habitual snoring and OSAHS were closely related to the occurrence of GDM[37]. Moderate-to-severe sleep breathing disorders in the first trimester of pregnancy elevated the risk of GDM compared with mild sleep disorders[36]. Sleep breathing disorders in both first and second trimesters were associated with GDM[38]. The screening tools for OSAHS in clinical use mainly included the Epworth Sleepiness Scale, the Berlin questionnaire, and the STOP-BANG questionnaire. Existing screening tools have limited subjective and objective assessments of sleep during pregnancy and are usually conducted by recording clinical data and standardising scale questionnaires. By contrast, the STOP-BANG questionnaire is simple to operate and has high sensitivity and specificity[39]. In future studies, more appropriate screening tools should be developed for use during pregnancy, or PSG should be used to demonstrate the relationship between OSAHS and GDM.
This study has some limitations. First, this study was a single-centre retrospective study. More research centres should be included to obtain further definitive results. Second, this study was only conducted on patients with DIP in China, leading to selection bias. Third, this study was a kind of investigation, so it was inevitable that there would be some bias.