The mechanisms of menstruation and parturition are very similar

What is it about?

Uniquely among animal species, women and also other primate females undergo a transformation of the uterine lining during every cycle, which is very similar to the transformation which happens during pregnancy. In contrast, in most other species, such transformation occurs only in presence of fetus. At the end of the secretory phase of the cycle, this transformed tissue is shed during menstruation, and the uterus undergoes renewal. Interestingly, not only the transformation of uterine tissue during pregnant and non pregnant cycles are similar, but also the processes which accompany the menstrual shedding and those which accompany birth show very distinct parallels.

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Why is it important?

While fetus certainly modifies some of the maternal biology, we show that much of the biology of pregnancy is already apparent in non-pregnant state, and thus could be studied in non-pregnant state. Many of the mechanisms of human pregnancy and particularly parturition are not understood, and are hard to study in human pregnancy- which hinders also our understanding of pregnancy complications. This study suggests that an intense study of menstrual, non-pregnant cycle may be able to reveal mechanisms not only of pregnancy, but also of parturition. Furthermore, the potential complications of pregnancy may be detectable already in the transformation during non pregnant cycle, offering a safe diagnostic tool before pregnancy occurs. Finally, the screening for defects of endometrial transformation (decidualization) can potentially be performed non invasively - by the analysis of shed menstrual tissue.

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