Things you should know!
How pregnancy works

Eggs are contained within the ovaries in a shell-like structure called a follicle.

Stimulated by follicle-stimulating hormone (FSH) released from the brain, multiple follicles grow simultaneously. However, usually only one follicle (the dominant follicle) leads to ovulation, while the others disappear.

These follicles release estrogen (follicle hormone).
Estrogen is a type of female hormone that thickens the uterine lining, preparing it to receive a fertilized egg.

When a large amount of estrogen is secreted, the brain rapidly releases luteinizing hormone (LH). Then, 24 to 36 hours later, the follicle ruptures and the egg is released from the ovary.
This is called ovulation.

After ovulation, the follicle becomes a corpus luteum and secretes a hormone called progesterone. Progesterone helps to prepare the uterine lining to create a more favorable environment for implantation.

If pregnancy does not occur, the corpus luteum becomes a corpus albicans after about 14 days, the thickened uterine lining sheds, and menstruation occurs.

The ovulated egg is taken up by the fimbriae at the end of the fallopian tube.
During ovulation, the fimbriae of the fallopian tube, which are shaped like sea anemones, gently touch the surface of the ovary, and it is believed that the egg is taken into the fallopian tube (this is called pickup).

The egg waits for sperm in the ampulla of the fallopian tube. If it does not find sperm, it will die after about 24 hours.

On the other hand, sperm ejaculated into the vagina travel through the cervix, then into the uterus, and finally into the fallopian tubes, aiming for the egg.

The sperm surrounds the multiple eggs it reaches. Then, only one sperm penetrates the egg.
This is "fertilization".

The fertilized egg undergoes repeated cell division and is transported to the uterus over 3 to 4 days by the fallopian tubes.

Once the fertilized egg reaches the uterus, it implants in the uterine lining, and pregnancy is established.

Within a few days of implantation, chorionic villi, the precursors of the placenta, begin to grow. When a large amount of the hormone hCG (human chorionic gonadotropin), secreted from these villi, is present in the urine, a pregnancy test will show a positive result.

Once implantation occurs, the body undergoes changes to prepare for the baby, such as menstruation stopping and breasts enlarging in preparation for breastfeeding.

The brain and ovaries work together to control hormone secretion, shaping a woman's menstrual cycle.

When the brain instructs the ovaries to "secrete female hormones (estrogen and progesterone)," the ovaries will secrete these hormones.

When the brain receives feedback from the ovaries that "female hormones have been secreted," it regulates the hormone levels by suppressing secretion when there are too many female hormones and increasing secretion when there are too few.