15.4 Gestation

During pregnancy the female body goes through a lot of changes. See here https://www.sciencealert.com/this-gif-shows-how-women-s-organs-shift-during-pregnancy for an animation of some of the changes and how organs shift during pregnancy. There are many other physiological changes that happen in a female body when pregnant. Many of pregnancy’s side effects are surprising. For example, very early in pregnancy the mother may find herself out of breath after relatively mild physical exertion. One of the reasons for this is that increasing progesterone levels in the blood cause the body to respond differently to carbon dioxide in the bloodstream. Also, throughout pregnancy, hemoglobin (the oxygen-binding protein in blood) in the fetus binds oxygen much more tightly than does the mother’s hemoglobin. Therefore, the fetus is taking oxygen away from the mother’s blood, causing the mother to breathe more deeply to replenish her oxygen.

A newly discovered side-effect of pregnancy is that some of the fetal cells will wind up in the mother’s tissues. In a recent study researchers looked for Y chromosome-containing cells in mothers who had given birth to sons –and found them in every tissue-type they investigated. The cells were present in low frequency, but the fact that they were there indicated that these cells had migrated from the fetus into the mother’s tissues. It is unknown how long after pregnancy the cells persist in the mother’s body and what effects these cells may have.

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The Evolution and Biology of Sex by Sehoya Cotner and Deena Wassenberg is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.