When does the placenta replace progesterone?

The hormone levels in women's bodies are different at different stages of pregnancy. For example, in the early stages of pregnancy, the progesterone level in the body is generally relatively high, which is also essential. If the progesterone level is low in the early stages of pregnancy, it may lead to miscarriage. As the pregnancy lasts longer and longer, the role of progesterone will slowly be replaced. In the late stages of pregnancy, this role will be completely replaced by the placenta. So when does the placenta begin to replace the role of progesterone?

When does the placenta replace progesterone?

Progesterone, commonly known as progesterone, is a hormone secreted by the corpus luteum of the ovary in the female body. It not only regulates the female endocrine system, but also promotes fetal growth and development in the early stages of pregnancy. What is the normal value of progesterone, what are the functions of progesterone, and when does the placenta replace progesterone?

Normal progesterone levels

Female progesterone is divided into progesterone reference values ​​for normal women's menstrual cycle, progesterone reference values ​​for pregnant women, and progesterone reference values ​​for menopausal women. Generally, the normal value of progesterone in the female follicular phase is 0.6-1.9nmol/L; the normal value during the ovulation phase is 2.40-9.40nmol/L; the normal value after ovulation is 20.7-102.4nmol/L; and the normal value at 7 weeks of pregnancy is 76.4±23.7nmol/L.

The role of progesterone

1. Immune protection. When a woman is in a normal pregnancy, progesterone increases, which prevents the embryo from being rejected by the mother and maintains the pregnancy. When there is a lack of progesterone, the embryo may be rejected by the mother and cause miscarriage.

2. Blastocyst implantation. During ovulation, under the action of progesterone secreted by the corpus luteum, the endometrium transforms from the proliferative phase to the secretory phase, making the endometrium receptive to embryo implantation.

3. Inhibit uterine contraction. Progesterone can change the permeability of the uterine cell membrane to ions, putting the membrane in a super-permeable state, thereby reducing the excitability and conductivity of the uterine muscle, and reducing the sensitivity of the uterine muscle to various stimuli (including oxytocin), thereby preventing the uterus from expelling the embryo and playing a role in preserving the fetus.

When does the placenta replace progesterone?

Progesterone plays an important role in fertility. Before the 10th week of pregnancy, progesterone is produced by the corpus luteum of the ovary. The corpus luteum of the ovary begins to secrete progesterone after ovulation. This period is the luteal phase after ovulation.

After 10 weeks of pregnancy, progesterone is mainly secreted by the placenta. At 12 weeks, the corpus luteum degenerates and is completely replaced by the placenta. Progesterone at this stage mainly induces immune protection mechanisms to prevent the embryo from being rejected by the mother. It can also reduce the sensitivity of uterine smooth muscle and play a role in maintaining pregnancy.

Therefore, when the pregnancy reaches 8-10 weeks, the progesterone secreted by the corpus luteum gradually decreases and is gradually replaced by the placenta, which gradually increases until full-term delivery.

The above is the editor’s introduction to progesterone during pregnancy and when the placenta replaces progesterone. I believe everyone has already understood it. Since both progesterone and placenta have the functions of promoting fetal growth and development, providing the nutrients needed by the fetus, and protecting the fetus, it is also necessary to pay attention to whether progesterone and placenta are in good condition during pregnancy. Once abnormalities are found, timely measures should be taken to deal with them.