How Does Pregnancy Happen?

Process of Fertilization

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The Process of Fertilization

When can you get pregnant? How high is the probability of getting pregnant? This article provides you with answers and information about fertilization and becoming pregnant.

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When Do You Get Pregnant?

Fertilization, aka conception, can only occur through sex during a woman’s so-called "fertile window". Throughout this time, the probability of getting pregnant increases. So, what is this "fertile window", and how do you detect it?

Cervical Mucus and the Fertile Window

During one’s monthly cycle, distinct indicators reveal when the fertile window begins. Many women will notice an increase in discharge, which can be quite liquid. This is due to the hormone, estrogen, which causes the thick mucus plug, sealing the cervix, to liquefy and increase cervical mucus production.

The exact timing of these changes within the cycle varies from woman to woman. This first phase of the cycle can also shift from one month to another. The female body is, after all, a very complex and amazing organism and does not function like a machine.

Should the woman have sexual intercourse during this time, the sperm would travel in the liquefied mucus, through the cervical canal and up to the fallopian tube, where it can survive up to five days.

This means that the fertile window begins as soon as the cervical mucus plug loosens and liquefies.

ℹ️ Note: Even if you go to the bathroom after having sex, and most of the sperm leaks back out, you can still become pregnant. Just one of the tiny sperm cells reaching the egg is all it takes.


During each menstrual cycle, estrogen causes several egg cells to mature. These are surrounded by a protective barrier called “follicles." One of these follicles usually becomes ready to be released. Once this follicle is mature, it bursts open, releasing an egg into the fallopian tube.

This process, called ovulation, takes place about 14 days before the next menstrual period. The egg, situated in the enlarged end of the fallopian tube, can now be fertilized within a maximum of 12-18 hours. This means that, in addition to the five days before ovulation, you can still become pregnant for about one day after ovulation.

How Do You Get Pregnant? - Process of Fertilization

For fertilization to occur, a sperm cell must come in contact and fuse with the egg cell. During the fusion, the genetic information of the maternal and paternal cell nuclei combine, forming new genetic information. Here, a single sperm is sufficient.

It takes approximately five days for the fertilized egg to move along the fallopian tube to the uterus to implant in the uterine lining. Once this has occurred, the pregnancy can soon be verified, even by using a standard pregnancy test.

Gradually the woman's body adjusts to the new situation and she may notice various signs of pregnancy. She will miss her next menstrual period.

👆Sometimes, more than one egg cell is released during ovulation within the same cycle. This is how multiple births can happen. If two eggs are released and fertilized, fraternal twins develop.
Identical twins form when a fertilized egg divides at an early stage. Both embryos then share the same genetic information. Usually, they implant separately in the uterus, and distinct amniotic cavities form. In rare cases, the twins share one amniotic cavity and placenta.

👧🏻 For more information, go to Twin Pregnancy

Can You Get Pregnant the First Time You Have Sex?

Maybe you have just had sex for the very first time; everything happened way too fast and now you don't know whether you could have gotten pregnant. In general, it is possible for you to get pregnant on the first time. Whether fertilization has actually occurred or not depends on whether you had sex during your fertile window.

Of course, it also depends on whether you used contraception and whether it worked. Without contraception, the probability of becoming pregnant from sex during your fertile window increases. Sometimes women can even get pregnant despite using contraception.

Determining the Date of Conception

The date of conception is essential for calculating the due date. Sometimes it also plays a role in determining paternity. Still, it is impossible to nail down the exact date of conception.

It is easiest to calculate your current week of pregnancy and the due date when there is only one possible date of conception. By charting your monthly cycle, and thereby determining your fertile window, you can narrow down the possible date of conception.

Most women can only provide the first day of the last period as a reference point. Since every woman’s cycle is different, it is improbable that the exact date of conception would be determined. Therefore, the physician will calculate the remainder of your pregnancy by adding 40 weeks to the first day of your last menstrual period (LMP). Your healthcare provider will also estimate the baby's age by its size. This will help your doctor to roughly determine the date of conception.

In some women, however, the egg matures more slowly, pushing back ovulation toward the end of the monthly cycle. In this case, basing the calculation on the last menstrual period would be quite inaccurate.

ℹ️ How to Calculate the Due Date:

Date of conception, take away seven days, take away three months, add one year. While calculating the due date, remember that plus/minus eight days are still considered “on track.”

To calculate the gestational age of your baby, start counting the weeks of pregnancy from the date of conception.

Am I Pregnant? Where Do I Go From Here?

Hopefully this article addressed some of your questions, and provided satisfactory answers.

🤰 If you are unsure whether you might be pregnant, feel free to take our Online Pregnancy Test. Simply state your symptoms and observations in a multiple-choice format and receive a detailed assessment, free of charge.

Perhaps you were not just looking for facts. You may have just found out you are pregnant. This has placed you in a difficult situation. You are thinking about abortion and looking into possible methods. You probably have many questions running through your mind.

Apart from your thoughts about abortion methods, you are probably dealing with a whole other set of feelings and worries. Maybe you don't know what to do next and are unsure what decision would be best for you.

You are not alone! Knowing you are understood, while looking at your situation objectively, may help you see things more clearly. Our goal is to provide you with judgement-free resources that allow you the freedom to find the path that is right for you.

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