Effects of Night Work on Urinary Excretion Rates of 6-Sulfatoxymelatonin, Norepinephrine and Estriol in Pregnant Women.

Abstract

It has been suggested that shift work, night work in particular, affects worker's psychophysical health. However, the effects of night work on the health of pregnant women are not physiologically well elucidated. The effects of night work on the biological function of pregnant women were studied in the present study. Three pregnant and six non-pregnant nurses that engaged in fastrotating shift system cooperated for the study. The 24-h urine samples were collected in two time frames, daytime (07:00 to 23:00) and nighttime (23:00 to 07:00) on the day shift, the night shift and the days off. Urinary concentrations of 6-sulfatoxymelatonin and norepinephrine were measured by enzyme-linked immunosorbent assay and estriol by radioimmunoassay. The excretion profiles of urinary 6-sulfatoxymelatonin in the pregnant and the non-pregnant women were altered on the night shift, which might relate the derangement of circadian rhythm of melatonin secretion. The urinary norepinephrine level during the night work was considerably higher in the pregnant women, which indicated the presence of higher physical burden in them due to the night work. The urinary estriol level was not significantly affected by shift, day/night and individual factors, and the effect of night work on urinary estriol level of the pregnant women remained uncertain. The results of the present study suggested that the night work of the pregnant shift workers should be much more relieved.

Circadian Variation of Melatonin, Light Exposure, and Diurnal Preference in Day and Night Shift Workers of Both Sexes

“…These results are in agreement with some (11-17) but not all (18,19,(30)(31)(32) previous studies, showing a reduction of aMT6s levels related to night shift work. Grundy and colleagues (19) found nonsignificant aMT6s differences between the day and night shift among female nurses working on a rapid rotating shift schedule.…”

Shift Work and Circadian Dysregulation of Reproduction

“…In general, shift work (especially rotating work or irregular hours) during pregnancy is associated with pre-term birth, low birth weight, and higher risk of spontaneous abortion or miscarriage (66). Although one previous study noted that night shift work does not affect urinary estradiol levels of pregnant hospital nurses (67, 68), this within-subjects study of nurses on a rapid rotation shift had too few subjects to be statistically persuasive, and a more recent meta-analysis that examined a large number of subjects found that the pooled risk estimates for pre-term delivery, low birth weight, and small for gestational age births increased with shift work [(15) but see also (14)]. In addition, examination of factory shift workers revealed that persistent rotating shifts led to lower birth weights and those infants in the bottom 20th percentile of birth weight were more likely to be born from mothers who work persistent rotating shifts (69).…”

Shift work: health, performance and safety problems, traditional countermeasures, and innovative management strategies to reduce circadian misalignment

“…However, although some studies of real shift workers do report reduced levels of melatonin,124–126 many do not 80,81,127–129. This discrepancy could be due to methodological differences between studies (eg, spot urine samples versus 24-hour urine collection), lack of statistical power to detect a modest effect size, or other factors such as light-exposure history.…”