How Pregnancy Happens

Pregnancy, Couple

How The Female Body Is Involved With Pregnancy

Ovaries are tiny sacs that contain immature ovum (egg cells), and found just outside the ends of each fallopian tube. There are usually millions of immature egg cells in females in their teens and 20s. Every month in the fertility/menstrual cycle, an ovary releases a developed egg cell, and this egg cell travels through one of the fallopian tubes. Ovaries alternately release an egg each cycle. There cannot be a pregnancy if there is no egg cell released, or won’t be within a few days.

There are also other things that happen simultaneously while an egg cell is in the fallopian tube or is on the way. The cervical mucus, the fluid around the cervix, become watery and stretchy. The os, the opening of the cervix, becomes softer and more open. Both of these two things should be happening so that the sperm cells can get to the egg cell, and they only occur in a short span of time, including the presence of an available egg cell—everything happens usually in just a few days in each cycle.

How The Male Body Is Involved With Pregnancy

Pregnancy may happen when a male ejaculates his semen inside the vaginal opening, or at least very directly to the vulva. Take note that semen and sperm cell are not the same thing. The semen is the fluid from the seminal vesicles, prostate gland, and Cowper’s gland, which all go through the urethra and out of the opening of the penis during ejaculation. Most of the time, semen contains sperm cells, but only make up less than 5% of semen. The fluid of the semen makes it possible for sperm cells to get out of the penis, and through the vagina. Aside from that, semen fluid also supplies the sperm cells with the nutrients and energy they need to endure the journey, and neutralizes factors that can obstruct the sperm cells such as traces of urine, and the vaginal environment.

The testicles produce millions of sperm cells each day. These sperm cells are very fragile and highly sensitive. They do not thrive when being moved around from place to place (like penis to hand, then hand to vulva), when temperatures shift, or when they are placed in a different environment besides the testes and special conditions designed to protect them.

Throughout the fertility (menstrual) cycle of a woman, there will be days when the cervical mucus is too thick and sticky to allow the sperm cells to push through, and the opening of the cervix is too narrow for them to get inside.

Sperm cells can last up to five days inside the vaginal environment. They wait within the vagina or other parts of the reproductive system when they get in too soon, and the egg cell and other conditions needed are not yet present.

It’s possible that there isn’t enough semen or viable sperm cells in the semen to make pregnancy possible. There are also a couple of factors that make the vagina, cervix, and uterus not sperm-friendly, just like how our bodies combat unhealthy bacteria and other potentially harmful visitors. This guarantees that only the strongest sperm makes it through the vaginal canal, and possibly fertilize the egg cell.

No matter how perfect the conditions may be, less than a thousand sperm cells out of the initial millions will successfully make it to the fallopian tubes, and just a few dozen of them will reach the outer membrane of the egg cell. This is why the male body produces so many sperm cells.

Fertilization Of The Egg Cell

As sperm cells pass the vagina and cervical opening, fewer and fewer of them become successful in getting through. When they get to the fallopian tubes, they will swim to either sides, which means that only half of them are likely to reach the egg cell. When in the fallopian tubes, these sperm cells are assisted by the contractions of the uterus to keep them moving, as well as by the cilia, very small finger-like filaments in the fallopian tubes that propel the sperm cells towards the egg cell. Chemicals inside the reproductive system also assist the sperm cells by giving them more energy.

There are approximately just fifty or so sperm cells left that surround the egg cell and attempt to enter the sac at this stage.

Sperm cells who successfully reached the healthy egg cell will attempt to push through the protective layers around it. They will compete until one sperm cell gets in the egg cell first and fertilizes it. The egg cell pulls the successful sperm cell inside by secreting a special enzyme that locks out the remaining sperm cells left trying to get in.

This stage is called fertilization of the egg, but it’s not considered a pregnancy yet.


About a day or so after fertilization, the united egg cell and sperm cell transform into a zygote. It stays in the fallopian tube and divides into many cells for a few more days. The zygote begins to move towards the uterus while still dividing. It then transforms into a blastocyst, a hollow ball of cells, implants itself in the uterine wall and attaches to the endometrium, and then becomes an embryo. The endometrium is the uterine lining shed during menstruation when there is no pregnancy. This stage of the process is commonly called conception or implantation.

Up to 50% of the time, fertilized eggs don’t divide or implant, and a pregnancy does not occur even without any interference from anyone or anything.

When all stages mentioned go smoothly, and the blastocyst successfully implants itself in the uterus, then a pregnancy has occurred.

The entire process usually takes five days to two weeks.



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