Elsevier

Biological Psychiatry

Volume 70, Issue 9, 1 November 2011, Pages 817-825
Biological Psychiatry

Archival Report
Should Neonates Sleep Alone?

https://doi.org/10.1016/j.biopsych.2011.06.018Get rights and content

Background

Maternal-neonate separation (MNS) in mammals is a model for studying the effects of stress on the development and function of physiological systems. In contrast, for humans, MNS is a Western norm and standard medical practice. However, the physiological impact of this is unknown. The physiological stress-response is orchestrated by the autonomic nervous system and heart rate variability (HRV) is a means of quantifying autonomic nervous system activity. Heart rate variability is influenced by level of arousal, which can be accurately quantified during sleep. Sleep is also essential for optimal early brain development.

Methods

To investigate the impact of MNS in humans, we measured HRV in 16 2-day-old full-term neonates sleeping in skin-to-skin contact with their mothers and sleeping alone, for 1 hour in each place, before discharge from hospital. Infant behavior was observed continuously and manually recorded according to a validated scale. Cardiac interbeat intervals and continuous electrocardiogram were recorded using two independent devices. Heart rate variability (taken only from sleep states to control for level of arousal) was analyzed in the frequency domain using a wavelet method.

Results

Results show a 176% increase in autonomic activity and an 86% decrease in quiet sleep duration during MNS compared with skin-to-skin contact.

Conclusions

Maternal-neonate separation is associated with a dramatic increase in HRV power, possibly indicative of central anxious autonomic arousal. Maternal-neonate separation also had a profoundly negative impact on quiet sleep duration. Maternal separation may be a stressor the human neonate is not well-evolved to cope with and may not be benign.

Section snippets

MNS in Primates

Dettling et al. (11) introduced an early adversity protocol wherein common marmoset monkeys experience daily 30- to 120-minute sessions of MNS from the 2nd to 28th day of life (total separation = 9 hours). Using this schedule, which approximates some human neonatal care (12), they found that MNS induced acute increases in urinary cortisol, epinephrine, and norepinephrine. After MNS, neonates spent more time in the suckling position, displayed less social play, and made more distress

Hidden Interactions in Humans

Pregnancy leads to endocrine priming of the brain and parturition triggers the expression of maternal and neonatal behaviors that are highly conserved across species (19). In humans, Widstrom et al. (20) and Winberg (21) describe how babies placed naked between their mother's breasts immediately after birth display stereotyped prefeeding behavior, comprising spontaneous sucking and rooting movements followed by crawling with their arms and pushing with their feet to locate the breast, attach to

Methods and Materials

Nineteen normal healthy full-term neonates (37+ weeks gestation) born by cesarean participated in a within-subject design. Mothers had no psychiatric/neurological history or physical complications and all babies had good Apgar scores (Table 1). Maternal-neonate dyads were a convenience sample by virtue of mothers staying 3 days in hospital postcesarean. Routine postnatal ward care for well neonates during sleep is loose swaddling in open bassinettes next to mother's bed. Mothers gave written

Results

Mothers ranged in age from 17 to 40 years (mean 27 ± 7.6), mean gravidity 2.6, range 1 to 5. Five had undergone cesarean previously and in five cases fetal distress was part of the cesarean indication. All 5-minute Apgar scores were ≥ 9 and there were no postnatal complications. The mean birth weight of the babies was 3295 ± 437g and their age when studied ranged from 42 to 74 hours (mean 53 ± 9.3). Subject details and sleep duration results across place are summarized in Table 1.

Discussion

We compared HRV power while controlling for sleep state and duration in 2-day-old babies across SSC and MNS. Results show a 176% increase in combined high- and low-frequency HRV power indicative of robust autonomic activation (44, 45) during sleep as a whole in MNS compared with SSC. Prior evidence comparing HRV across SSC and MNS is extremely limited and mostly confounded by a critical lack of control for level of arousal. Begum et al. (51) found significantly decreased LF and HF HRV power in

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