Updated on December 28, 2022

How do egg cells and sperm cells meet?
Each stage of the journey from ovulation to fertilization

  • ovulation
  • implantation
  • Probability of pregnancy

Clock illustrationReading time: 4 minutes

How do egg and sperm meet? The journey from ovulation to fertilization.

Table of Contents

Dr. Masayuki Kinutani, Director of Kinutani Obstetrics and Gynecology Clinic

Dr. Masayuki Kinutani, Director of Kinutani Obstetrics and Gynecology Clinic

Supervision

Director, Kinutani Obstetrics and Gynecology Clinic (Medical Corporation)
​Mr. Masayuki Kinutani

After graduating from Ehime University School of Medicine, she worked at the Department of Obstetrics and Gynecology at Hiroshima University School of Medicine and the Sanno Hospital Reproduction Center, before studying advanced reproductive technology in Canada, the United States, and the United Kingdom. In 2002, she became the director of Kinutani Obstetrics and Gynecology Clinic. She is a certified obstetrician and gynecologist by the Japan Society of Obstetrics and Gynecology and a certified reproductive medicine specialist by the Japan Society for Reproductive Medicine.

Ovulation, egg retrieval

Illustration of a woman who is troubled.

How does the body prepare for ovulation?

Mr. Masayuki Kinutani

When menstruation begins, the hypothalamus in the brain first sends a signal (GnRH) to the ovaries to secrete hormones that stimulate ovarian function. The pituitary gland then secretes follicle-stimulating hormone (FSH), which is necessary for creating mature eggs, towards the ovaries. This FSH stimulation causes the small follicles to grow larger over about two weeks and become mature follicles.

Once the follicle is fully mature, the pituitary gland suddenly releases a large amount of luteinizing hormone (LH), which signals the body to ovulate, leading to ovulation.

The relationship between hormones and ovulation

Illustration of a woman who is troubled.

Where does the egg go after it's been released during ovulation?

Mr. Masayuki Kinutani

When the ovarian is ready to ovulate, the fimbriae, the end of the fallopian tube which is shaped like a sea anemone, cover the ovary.
When a follicle ruptures and an egg is released during ovulation, the fimbriae of the fallopian tube draw the egg in and take it into the fallopian tube. This function is what is known as "egg pickup."​
The egg, once taken into the fallopian tube, is then transported to the ampulla, a slightly swollen part of the fallopian tube.

Egg pickup

Illustration of a woman who is troubled.

How long does it take for an egg to be transported to the ampulla of the fallopian tube?

Mr. Masayuki Kinutani

The distance from ovulation to the ampulla of the fallopian tube is probably short, so it shouldn't take very long.
However, since the egg pickup process cannot be seen with the naked eye, there is currently no test to confirm whether the pickup function is working properly. In cases of unexplained infertility, a problem with this pickup function may be the cause.

From the meeting of sperm and egg to implantation

Illustration of a woman who is troubled.

Next, please explain how the sperm, once ejaculated, get to the egg!

Mr. Masayuki Kinutani

First, ejaculated semen does not enter the uterus. Then, only sperm swim up the cervix, which is about 3-4 cm long and connects the vagina to the uterus, and enter the uterus.

At this time, the cervical mucus secreted from the wall of the cervix plays a very important role. Normally, cervical mucus protects the uterus from bacteria and other pathogens, but as ovulation approaches, the amount of mucus secreted increases, and it becomes clear, watery, and stretchy, which helps sperm enter the uterus.

The sperm that enter the uterus then travel through the fallopian tubes, reaching the ampulla of the fallopian tube where the ovulated egg is transported, and wait there until the egg arrives.

Sperm pathway

Illustration of a woman who is troubled.

So the semen doesn't enter the uterus directly, right...?
If tiny sperm have to swim on their own, it seems like it would take quite a long time.

Mr. Masayuki Kinutani

Since the distance from the opening of the uterus to the ampulla of the fallopian tube is about 18 cm, it would take a considerable amount of time for sperm to swim that distance on their own.
However, it is thought that the uterus actually contracts, acting as a pump to help sperm travel to the fallopian tubes, and that sperm can reach the ampulla of the fallopian tube within a few minutes to a few hours after ejaculation.

Illustration of a woman who is troubled.

I was surprised it was faster than I expected!
The egg and sperm finally meet after going through this process.

Mr. Masayuki Kinutani

When sperm and egg meet in the ampulla of the fallopian tube, the sperm penetrates the egg's outer layer headfirst, and the sperm and egg become one. This is called fertilization.
The fertilized egg grows in the fallopian tube through repeated cell division, and implants in the uterine lining 5 to 7 days after fertilization, leading to pregnancy.

To increase the chances of pregnancy during fertilization

Illustration of a woman who is troubled.

I want to increase my chances of getting pregnant, even just a little. Could you please tell me the key points for successful fertilization?

Mr. Masayuki Kinutani

One thing you can do yourself is to maximize the time that the sperm ejaculated into the vagina is in contact with the cervical mucus, so that as many sperm as possible can enter the uterus. Specifically, instead of getting up and moving around immediately after intercourse, take some time to lie down with your hips slightly elevated using a pillow or something similar. This will help prevent the ejaculated semen from leaking out, allowing the sperm to stay in contact with the cervical mucus for a longer period.

Another important point is to understand that both the ovulated egg and the ejaculated sperm have a limited lifespan, and to time intercourse accordingly to ensure they meet successfully. I'll discuss this in more detail next time.

Illustration of a woman

I'm curious about the best timing for sex!
See you next time!

I want to know the correct answer!
Best timing for intercourse when trying to conceive

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