Melatonin level and pattern in postpartum versus nonpregnant nulliparous women.

OBJECTIVE

To compare 24-hour melatonin level and timing in postpartum and nonpregnant nulliparous women. Melatonin release provides information regarding circadian rhythm timing, which influences health.

DESIGN

2-group comparison of data derived from intensive within-subject data collection.

SETTING

Participants' typical daily environment.

PARTICIPANTS

38 postpartum and 20 nonpregnant nulliparous women. Mothers' infants were 4 to 10 weeks of postnatal age.

MAIN OUTCOME MEASURES

Urinary 6-sulfatoxymelatonin assayed from each voiding and corrected for volume using creatinine.

RESULTS

Postpartum women had significantly higher baseline, lower maximum, lower percent rise, and differing pattern of 6-sulfatoxymelatonin than nonpregnant nulliparous women.

CONCLUSION

Differences in melatonin suggest possible circadian rhythm disruption in the postnatal period.