Normal postpartum sleep is characterized by marked sleep fragmentation due to infant care, which continues until the infant sleeps through the night. Relative to pregnancy, women sleep less at night and more during the day and are awake more during the night in the early postpartum. Maternal sleep does not appear to differ by nighttime feeding method (i.e., breastfeeding vs. bottle feeding) [24], and results from one study suggest that women who breastfeed exclusively sleep more during early postpartum relative to women who use formula some of the time [25]. Of note, while sleep is significantly disrupted in postpartum women, total sleep time is preserved, and thus women experience sleep fragmentation rather than sleep deprivation. Certainly other sleep disorders may continue following delivery although RLS generally resolves. Since SDB is related to excess weight, many women continue to have SDB symptoms in the postpartum period while they still carry excess weight. However, SDB does not necessarily resolve in the immediate postpartum period in women in whom it was moderate–severe during pregnancy. It is typically these women who seek treatment following delivery.

Many factors unique to the postpartum period may trigger insomnia and perpetuate it over time. Rapid hormonal changes following delivery, particularly the precipitous decline of progesterone (known for its hypnotic effects), may contribute to wakefulness. Caring for an infant who is not yet entrained to a 24-h day may lead to dysregulation of circadian rhythms via variable bed and wake times, low light levels during the day, and exposure to bright light at night. Anticipation of infant awakenings can contribute to hyperarousal and difficulty falling asleep. Behaviors to manage sleep loss experienced during the postpartum may perpetuate insomnia by weakening sleep drive, dysregulating circadian rhythms, and conditioning the bed as a place for wakefulness. Such behaviors include spending long periods of time in bed awake, use of the bed for activities other than sleep, irregular sleep–wake times, excessive use of caffeine, and reliance on medications for sleep.

The sleep fragmentation and significant fatigue that affect almost all women in the postpartum period are major contributors to the onset of mood disturbance. In the early postpartum period, infant sleep is evenly distributed across the day and night; thus, the caregiver’s sleep is significantly fragmented during this time. Sleep fragmentation is associated with daytime sleepiness, fatigue, neurobehavioral deficits, and postpartum depression. While total sleep time remains constant across the initial postpartum months, sleep efficiency appears to improve. Although sleep fragmentation constitutes normal development during the postpartum period, persistent difficulty in falling asleep or returning to sleep when the infant is sleeping may signal insomnia.

Insomnia during the postpartum period is associated with depression and anxiety symptoms. Difficulty falling asleep may be more closely linked to postpartum depression than other insomnia symptoms [26]. Poor sleep quality in the first 4 months postpartum significantly increases the risk of relapse to postpartum depression in women with a past history of depression [27]. In rare cases, sleep loss may precipitate postpartum psychosis, an uncommon but serious psychiatric illness. Maternal depression subsequently increases the risk for negative parent–infant interactions, adverse infant emotional and cognitive outcomes, as well as failure to thrive. Thus, it is important to consider sleep disruption as a precipitating factor when addressing postpartum depression.

Understanding the influence of the infant is important in assessing sleep disturbances in postpartum women. For example, women who report sleep problems that occur due to their infant’s sleep may benefit from infant-focused interventions. In contrast, women who describe difficulty falling asleep or staying asleep when the infant is asleep or not otherwise a factor may be experiencing a sleep disorder such as insomnia. Light exposure during the day and at night should also be assessed. Many postpartum women remain in dim light during the day and are exposed to short bursts of bright light at night when caring for their infant. Exposure to bright light at night suppresses melatonin, a hormone secreted during the night that provides the body’s internal biological signal of darkness. Exposure to light resets the circadian rhythm of melatonin and acutely inhibits melatonin synthesis. Thus, patterns of low light levels during the day, combined with periods of bioactive light at night, may cause dysregulation of circadian rhythms. Encouraging postpartum women to spend time with their infant in bright light during the day and to limit bright light exposure at night—such use of red light (which is believed to prevent melatonin suppression)—may improve sleep as well as mood.

It should again be emphasized that disrupted maternal sleep in the postpartum period is a normal developmental trajectory. While there is a high prevalence of parent-reported infant sleep problems during this time, it is most likely that it is not the infant with sleep problems per se, but rather the unrealistic expectations by the parents of normal infant sleep patterns. Education regarding normal sleep patterns of both the infant and the new mother should be provided during pregnancy so that the mother has realistic expectations of sleep in the initial postpartum period. Although education is important, alone it may not be sufficient in many cases. Women with residual symptoms of SDB should be evaluated and, if obstructive sleep apnea is present, treated with PAP.