**1. Introduction: sleep disorders and changes of circadian rhythms during pregnancy**

Sleep architecture and sleep regulation mechanisms are different depending on gender. Indeed, women are used to perceive worse subjective sleep quality when compared to men, as demonstrated by shorter circadian period in this population. Moreover, female tend go to bed earlier and fall asleep later and present a larger melatonin production pattern [1–6]. The prevalence of sleep disorders is also different in males and females. Hence, some disturbances, such as hypersomnia, insomnia, parasomnia, and restless legs syndrome are more frequent in women, while narcolepsy, arousal disorders, Klein-Levine syndrome, and sleep behaviour disorder with rapid eye movement are more frequent in men [7–9].

Pregnancy and perinatal period (one year after childbirth) represent particularly vulnerable periods for women, due to anatomical, hormonal, and psychological changes that infuence women's global health [10]. Poor sleep is a common condition during this period especially during the third trimester [11]. Indeed, 52-61% of women during the last eight weeks of pregnancy show reduced and poor sleep quality, with even higher prevalence among women with a diagnosis of current or previous depressive disorder or history of smoking [7].

Moreover, pre-existing sleep disorders may become more serious during pregnancy and these disturbances increase as the gestational period progresses. Sleep changes in pregnancy are detected by polysomnogram measurements, which during the third trimester usually show an increase in wakefulness after sleep onset and a decrease in Rapid Eye Movement (REM) sleep compared to non-pregnant women [12].

During pregnancy, sleep disorders may contribute to the occurrence of irritability, diurnal hypersomnia with reduction in efficiency, abuse of hypnotic/anxiolytic drugs, impulse control disturbances, also leading to the development of mood

disorders and to increased suicidal ideation with a risk of suicidal behaviours [12, 13]. Moreover, low birth weight and morphological abnormalities may occur in the foetus and his/her circadian rhythms may also be disrupted, since these are regulated by maternal factors. To note, the foetus does not produce melatonin, a hormone with an essential role in sleep–wake rhythm regulation. Further circadian rhythms that may be altered as consequence of sleep–wake disorders are: body temperature, physical activities, eating patterns, and hormone secretion, particularly melatonin and glucocorticoids These alterations can also explain why pregnant shift-workers display a higher risk of low birth weight, spontaneous abortion, and premature birth, and have sons affected by insomnia or low-birth weight, but also a higher risk of infertility, miscarriage, and pre-eclampsia [7, 13–17].

Previous studies reported different data about the incidence of sleep disorders during pregnancy, but consensus was reached about pregnant women having more disturbed sleep than during other times in their lives. Particularly, about 25% of pregnant women report significant sleep disturbances during the first trimester, with rates rising up to almost 75% during the third trimester [18]. Some authors also argue that up to 97% women report disturbed sleep during pregnancy [19].

## **2. Factors affecting sleep during pregnancy and action of sexual hormones**

Poor sleep quality and insufficient sleep duration are common in the general population and can result from environmental and psychosocial factors, as well as from medical and psychiatric disorders. During pregnancy, possible causes of sleep complaints, such as hormone release alterations, increase their incidence. A relevant role is also played by anatomical and physiological changes.

Sleep disturbances seem to be caused by different factors during the three trimesters of gestation. During the first trimester, the main causes of disturbed sleep are vomiting, nausea, and history of infertility. Gastrointestinal disorders appear to be sleep-disturbing factors also in the second trimester [11], whilst in the last trimester women with muscular-skeletal pain, overweight, restless legs, reflux, uncomfortable positions, and snoring present more sleep disturbances [20].

The main precipitating factors are listed below:



#### **Table 1.**

*Overview of the development of new pathological conditions in pregnancy from sleep-altering physiopathological conditions.*

### **3. Consequences of sleep disorders during pregnancy on women**

Sleep is a fine mechanism regulated by different factors and its alteration presents consequences for both the mother and the child. Furthermore, discomfort and frustration experienced by women may also influence their partners, who may in turn present sleep disorders. The most frequent consequences of sleep disorders during pregnancy are discussed in this section.

#### **3.1 Affective disorders and suicidal ideation**

Sleep plays a fundamental role in learning, by influencing the development new neuronal circuits. Subsequently, sleep restriction can lead to a disruption of neuroplasticity, thus triggering some among the pathophysiological mechanisms responsible for the development of depression. The pathophysiological mechanisms underlying both sleep disorders and depression are regulated by common neurobiological systems, i.e., hyperactivity of the hypothalamic–pituitary–adrenal axis, dysfunction of serotoninergic system, and hyperactivity of noradrenergic system [25]. Indeed, these specific systems play a role in the regulation of basic emotional responses, such as fear and reward. Therefore, insomnia may compromise adequate emotional processing and may underpin a greater susceptibility to develop psychopathology, particularly anxiety and depressive symptoms and, to a lesser extent, psychosis and substance or alcohol abuse [26].

This may explain why disturbed sleep is reported in up to 90% subjects with depression and REM sleep disturbances may precede the clinical expression of depression itself, aiding the identification of individuals at high risk for developing the disease [27].

However, there are conflicting studies on the correlation between sleep disorders and depression during pregnancy. In previous reports, insomnia did not predict post-partum depression in women with no prior history of depression, as evidenced in a longitudinal study carried out in women at the 17th and 32nd week of gestation and eight weeks after childbirth. This study underlined women suffering from depression before pregnancy also reported more severe residual insomnia symptoms compared to those who scored low for depression at both times [28]. On the contrary, another study showed that poor sleep may represent a potential risk factor for depression during both the prenatal and post-partum period [29]. An Italian study reports that pregnant women with high stress-related sleep reactivity, compared to those with low reactivity, reported more symptoms of insomnia, higher rates of depression, anxiety, and suicidality [13].

**Post-partum depression (PPD)** is a condition that affects 10-15% of women during pregnancy. It presents with depressive symptoms, such as low mood, hopelessness, sleep disturbances, emotional lability, feelings of guilt, changes in appetite, suicidal ideation, memory loss, fatigue, difficulty in concentrating, and irritability, usually compromising the mother-baby relationship [30]. Physiological, hormonal and metabolic changes occurring during pregnancy often interrupt mother's sleep–wake cycle, and the loss of the sedative effects of endogenous progesterone can lead to post-partum insomnia. In addition, women may wake up several times during the night to take care of their baby and all these factors can contribute to the development of depressive symptoms. Women with a previous history of mood disorders and obsessive–compulsive disorder, as well as women who already presented circadian rhythm disruptions, were also more susceptible to developing this condition. The correlation between sleep disorders and post-partum depression can also be demonstrated by the evidence that treatments for sleep disturbances in pregnant women, i.e. trazodone or

#### *Sleep Disorders in Pregnancy DOI: http://dx.doi.org/10.5772/intechopen.100300*

diphenhydramine, may contribute to a consequent reduction in symptoms of post-partum depression [12, 30].

**Suicidal behaviour** is the leading cause of injury and death during pregnancy and suicidal ideation is often considered a key predictor of subsequent suicide attempts [25]. During pregnancy, the prevalence of suicidal ideation can reach between 5 and 14%, which appears to be twice as high as in women without sleep disorders [25, 31]. The presence of comorbid depression leads to a further increase of suicidal risk. Main predisposing factors that lead a pregnant woman to plan suicide are: history of abuse, accidental pregnancy, marital status, family dynamics, low level of education, partner violence, mood disorders, and sleep disorders [25]. The correlation between sleep and suicidal ideation or behaviour can be explained since poor sleep quality may contribute to changes in cognitive, emotional and behavioural processes, and the resulting irritability and emotional lability may encourage suicidal attitude [25, 31].
