Sleep disorders, melatonin, and pregnancy complications

Problem statement. The pineal gland produces the important hormone melatonin, which maintains the human body's circadian rhythm. In pregnant women, melatonin is also produced by the placenta. The effect of melatonin deficiency in case of pregnancy disorders, such as intrauterine growth restriction (IUGR) of fetus and preeclampsia (PE), has been insufficiently studied.

Methods. We analyzed the recent publications dedicated to the problem.

Results. In analyzed papers, the relevant information is presented as follows: the morning concentration of melatonin in the blood of pregnant women with IUGR significantly reduces, compared to healthy pregnant women, which authors consider to be caused mostly by placental dysfunction. Changes in the functioning of the pineal gland in patients with IUGR are clinically expressed as sleep disorders and confirmed by a significant decrease of melatonin concentrations in saliva taken at night, in comparison with women with non-complicated pregnancies. Sleep disorders in women with IUGR manifest early during pregnancy, mostly in pregnancy term 22–30 weeks. Changes in melatonin concentrations in such patients are accompanied by a lowering of the concentrations of placental growth factor (PlGF) in blood and with increase of the blood levels of cytokines, namely proinflammatory TNF-α, IL-1-β and IL-6, compared to healthy pregnant women. In placental tissue melatonin receptors 1A and 1B are significantly less expressed in the case that pregnancy is complicated with IUGR, which is confirmed by changes in the optical density of these receptors.

In publications dedicated to preeclampsia, it is stated that the morning concentrations of melatonin and PlGF were also significantly lower in the blood of women with PE compared to healthy pregnant women. The authors suggest that alterations in the placental production of melatonin and PlGF may contribute to the development of preeclampsia. In contrast, higher levels of the pro-inflammatory cytokine interleukin-6 (IL-6) and the anti-inflammatory cytokine interleukin-10 (IL-10) were observed in preeclampsia patients' blood, compared to the healthy pregnant women. Significant sleep disorders were also described in patients with PE.

Conclusion. Melatonin is a hormone that plays a very important role in the mechanisms of development of such pregnancy complications as IUGR and PE. Further studies are needed to describe its role in the pathways of mentioned disorders of human pregnancy. Sleep disorders, if present in a pregnant patient, should not be ignored by clinicians.