7.1 Physiological changes in the female reproductive system during pregnancy
7.1.1 Changes in oestrogen and progesterone
In Study Sessions 3, 4 and 5 you learned about the main female reproductive hormones, oestrogen and progesterone, and their functions in preparing the uterus for pregnancy. Oestrogen and progesterone are also the chief hormones throughout pregnancy.
A woman will produce more oestrogen during one pregnancy than throughout her entire life when not pregnant. During pregnancy, oestrogen promotes maternal blood flow within the uterus and the placenta.
How does oestrogen play an important role in the development of the fetus?
By promoting maternal blood flow to the uterus and placenta it ensures that the fetus is supplied with nutrients and oxygen for its development, and that waste products from the fetus are removed in the mother’s blood. (You learned about this in Study Session 5.)
A pregnant woman’s progesterone levels are also very high. Among other effects, high levels of progesterone cause some internal structures to increase in size, including the uterus, enabling it to accommodate a full-term baby. It has other effects on the blood vessels and joints, which we will discuss later in this study session.