What changes do pregnancy hormones trigger in the body?

Pregnancy hormones trigger changes such as breast enlargement, increased blood volume, and changes in the uterus and cervix.

Pregnancy hormones, primarily human chorionic gonadotropin (hCG), progesterone, and oestrogen, play crucial roles in the physiological changes that occur during pregnancy. These hormones are produced by the placenta and the ovaries and are essential for maintaining pregnancy and preparing the body for childbirth.

Human chorionic gonadotropin (hCG) is the hormone that pregnancy tests detect. It is produced by the cells that form the placenta. This hormone stimulates the corpus luteum (the remains of the follicle that has released an egg) to produce progesterone, which is essential for maintaining the pregnancy in its early stages. hCG levels rise rapidly in the first trimester and then decrease as the pregnancy progresses.

Progesterone is another key hormone during pregnancy. It helps to maintain the lining of the uterus and suppresses the immune system to prevent it from rejecting the embryo. Progesterone also relaxes the muscles of the uterus to prevent contractions that could lead to a miscarriage. As the pregnancy progresses, progesterone helps to prepare the breasts for milk production.

Oestrogen, particularly oestradiol, is produced in increasing amounts as the pregnancy progresses. It stimulates the growth of the uterus and the development of the mammary glands in preparation for breastfeeding. Oestrogen also plays a role in increasing the blood supply to the uterus and the development of the placenta.

Another hormone, relaxin, is produced by the ovaries and the placenta. It relaxes the ligaments in the pelvis and softens and widens the cervix to prepare the body for childbirth. It also inhibits contractions in the uterus.

In addition to these, other hormones such as prolactin (which prepares the breasts for milk production), oxytocin (which triggers labour and helps with breastfeeding), and human placental lactogen (which provides nutrients to the fetus) also play significant roles during pregnancy. These hormonal changes are essential for the development of the fetus and the physiological changes in the mother's body.