Fertilization and Pregnancy

Women, part 1

*This is part 1 in the series about women. This part will be to inform the reader about a biological process many women and the female body will experience and a requirement for it: pregnancy and fertilization.

We don’t have to look very far to find the importance of women: they give us life. Literally. The word ‘literally’ is not one of my favourite things to hear. This is because many people do not use it in the correct way. But here, the word is in its place, because we do not live until given by women. So let’s start there: at (the biological beauty of) fertilization and pregnancy. For which you need a woman (or someone that was born in a female body).

Pregnancy is derived from the latin words ‘prae gnantem’, meaning ‘before birth’. The process is so beautiful, that I often call it a miracle. Even so; successful pregnancies happen around 123 million times a year (or 250 times a minute (Sex, Explained, 2020a)). On average a woman has 2.69 children (World Health Organization, 2007). Those children have to be born once. I have learned a lot from the research described below and pregnancy and fertilization has only become more beautiful and miraculous to me. 

The beauty of pregnancy (photo by Georgia Maciel).

What you should realise is that this all happens in the female body. Therefore, in my view, women are already a parent of their still unborn child during their pregnancy. Men on the other hand become a parent of the child when the child is born. During pregnancy the female body and the mother make some incredible efforts to keep the embryo or fetus healthy and safe. Without those efforts, the fetus won’t become viable. These efforts include the pain almost all women have to endure during pregnancy, accepting the changes to their body and hormone level, accepting a partner that is not always very supportive (during this time), making it possible that nutrition and oxygen can go to the bloodstream of the embryo/fetus via the bloodstream of the mother, not ingest anything that could be damaging (the health) of the baby, go on living as normal as possible for the most time of pregnancy, all the way up to probably enduring pain again when giving birth (or as the Spanish say it so poetically: ‘dar la luz’, literally translated: ‘giving the light’). But it’s all worth it. Which I notice especially when I look at women.

The beauty of women (photo by ELEVATE).

I am sorry if there are women reading this piece who can’t get pregnant and feel very sad about it. Especially after reading this. Just know that we live in modern times and there is science that can help you out. It isn’t a guarantee, but it has chance and thus can give you hope. We will also discuss these ‘scientific’ fertilizations, but let’s first start with the ‘natural’ one.  

Fertilization can happen after sex. Almost 250 – 300 million sperm cells (Khan Academy, 2015; Nucleus medical media, 2013) from the man insert the female body through the vagina. A portion of the cells find their way out of the vagina or die here.

Diagram showing the female reproductive tract. The path of the sperm is highlighted via a blue arrow.
The path the sperm travels to fertilize an egg (Khan Academy, 2015).

The cervix (the gateway from the vagina to the uterus), normally closed, is open for a few days when the woman ovulate. Still, it denies access to most of the sperm cells. The cervix is essential for protecting the sperm cells on their quest to the egg. During pregnancy, it can stretch up to five times the stretchiness of the ‘nonpregnant stretchiness’ (Sex, Explained, 2020a).

Two pieces of tissue from the cervix are tested on strechiness. On te left: nonpregnant tissue, on the right: pregnant tissue. The pregnant tissue is on average five times strechier than the nonpregnant tissue (Sex, Explained, 2020a).

After the cervix, the sperm enters the uterus. Here they are not so much propelled forward by their tail as helped forward by muscular contractions of the uterus (Sex, Explained, 2020b; Nucleus medical media, 2013).

Of those 250 – 300 million original sperm cells that started ‘the race’ to the egg, only about one in one million sperm cells are able to make it to the fallopian tube where the egg can be fertilized (Khan Academy, 2015). There, the egg is surrounded by sperm that overcame all obstacles. Normally a few dozen. However, only one sperm cell will penetrate and fertilize the egg to become one cell. This cell is called a ‘zygote’ in medical terms (National Geographic, 2018; Nucleus medical media, 2013). For this, the egg first has to have been released (the ovulation). This is what happens one time a month (at least, that’s convenient for us to say). Later on we will see that the release of an egg does not have to be at all constant in time. It can take longer or shorter, but on average is 26 days (Jukic et al., 2007).
Anyway, this is why a woman can only get pregnant within a specific period of ‘the month’. In general a period within five days after the ejaculation of the man’s sperm into the woman vagina, if she ovulates during that time. This is because an egg is only viable for maximum 24 hours (The Royal Women’s Hospital, z.d.; et al.). The sperm however, can live for a maximum of five days in the woman’s tract (Galan, R. N. N., 2017).

When the woman is ovulating, the body makes it ‘easier’ in all sorts of ways for the sperm to pass the vagina and uterus. For instance by making it more ‘watery’. If the woman isn’t ovulating, there is no need for the sperm to reach the egg in the first place (because there is no egg that can be fertilized). In this case it is much more important to focus on fighting of pathogens, since the vagina and uterus are very prone to infections (Khan Academy, 2015).

A woman in general is fertile between the age of 12 and 50 years old. However, chances on pregnancy drop fast after the age of 35 (Sense, n.d.). In the fertile period, an egg will be released every ‘month’. So, the woman will also menstruate every ‘month’ within this period, if she doesn’t get pregnant. This is when she also isn’t taking hormones via the (contraceptive) pill or vaginal, which will be discussed in part 2.2 of this series. The menstrual cycle and period will be further discussed in part 2.1 and 2.2.

‘Scientific’ fertilization
The way from the sperm cell to the egg in the human body is ‘a labyrinth full of obstacles’. Unfortunately, it is not always possible for a couple to get pregnant via the ‘natural’ way. This could be because of the infertility of the man or the woman. Medical research made it possible to remove some of the obstacles with the help of drugs and medical procedures. But in 1978, once again, science stepped in to help out. ‘The labyrinth’ was replaced for ‘the laboratorium’. What if we didn’t need the female body to make a fertilization of the female egg possible?
In In-Vitro Fertilization (IVF), from the latin ‘in glass’, a female egg retrieved from the body is mixed with male sperm in the lab. After fertilization, it is planted back into the uterus.
A few years later, Intracytoplasmic Sperm Injection (ICSI), made it possible to insert a single sperm cell (!) into the female egg (Sex, Explained, 2020b). Before you read on, just realise how incredible this is. A sperm cell is around 50μm in length and 10,000 times smaller than a female egg. Around 100,000 times smaller than 1.2mm (!) (Khan Academy, 2015). The science of IVF and ICSI could lead to more diverse ways of getting and raising children.

Schematische weergave van het verschil tussenI CSI en IVF bevruchting
IVF on the left and ICSI on the right. The differences dispayed in drawing . In IVF, sperm cells surround the egg and one fertilizes it. In ICSI, one sperm cell is injected in the egg (24baby, z.d.)

Also the freezing of eggs can help stimulate the chances in getting pregnant in this way. It can make women fertile for a longer period of time. However, there is even a new form of freezing; ovarian tissue freezing. Here, part of the ovary is freezed and later transplanted back into the female body. And yes, this tissue starts releasing eggs again. In this way, women can get pregnant without IVF. And they have been and also given birth already (Sex, Explained, 2020b). Still, there are some bumps in the road of ‘scientific fertilization’. Such as the costs and the possibility of raising a family in an non-traditional way, which unfortunately, not every government supports.         

If the egg is fertilized, the one cell becomes two, than four, than eight and so on. After almost a week, the cell functions become different from each other and the cells differentiate. Meanwhile (in a natural fertilization), the egg travels through the fallopian tube, to the uterus to plant itself in the functional layer of the uterine lining (Nature videos, 2018). It is now an embryo in combination with the placenta.

The embryo embedded in the placenta that lay together on the uterine lining (National Geographic, 2018).

Be aware: the placenta is an organ formed by the cells of the embryo itself! It is not already present in the womb before the ‘nesting’ of the embryo (NHS, 2018). The placenta provides what comes in and out of the embryo. It is thus of essential importance for the viability of the embryo (National Geographic, 2018). Around day 10, the embryo is able to support itself without the help from the mother’s tissues. The embryo also binds more strongly to the wall of the uterus. A few days after this, holes are created for the mother’s blood vessels to come in. This is to supply the embryo with necessary oxygen and take away the waste produced by the embryo (Nature videos, 2018).

After about a month, the first hormone (that is only present during pregnancy) will kick in; human chorionic gonadotropin (hCG). It has its peak, usually in the third month. Morning sickness is thought of to come from this hormone (Daley, K, 2019). Many parts of the embryo will develop in the later part of the first trimester, such as the brain. From this moment on, the embryo is (medically) often referred to as the fetus (Cleveland Clinic, n.d.). At the end of this trimester which is after around 12 weeks, the embryo has already many aspects of a baby (National Geographic, 2018). See picture below .

A photo of the ultrasound of a 12 weeks old fetus. This is the one of my niece, who is born now. A more recent photo of her can be seen at the end of this piece.

In the second trimester, the baby can be felt moving and the hearing develops. Also, the fetus will double in size within this period, that last until week 27 (National Geographic, 2018).

In the last period before labour (the third trimester), the i’s will be dotted and the t’s will be crossed. In this time the mass of the baby increases rapidly and the mother’s organs make room for the baby. The bones of the baby harden, except for the skull and the baby is tipped head down, to prepare for delivery. After this, the baby is delivered together with the placenta (National Geographic, 2018).

It’s unfair to let the process of childbirth happen in one sentence. It is far from ‘a walk in the park’. Throughout evolution, humans have gotten bigger and bigger brains and we have learned to walk on two feet. This is functional, but not ideal for childbirth, since skuls became bigger and the pelvises became more narrow (Sex, Explained, 2020a). All and all, it means: less space for the baby and more pain during labour. 

C-sections are growing in popularity and are now being done in more than 20% of the child deliveries. In some countries, such as Brazil, for even more than 50% of the time. In private hospitals there, even around 83% of the time. It is true that maternal mortality rates drop in countries with more C-sections, but only up to 19%. Above that, it doesn’t make a difference, suggesting that many C-sections are medically unnecessary (Sex, Explained, 2020a). And unplanned C-sections can cause posttraumatic stress and depression (Tonei, V., 2019). The presence of trained birth coaches during a woman’s labour lowers the chance of a C-section by 51% (Scott, et al., 1999). This because the woman is supported. Also, trained birth coaches make sure a woman’s wishes are being respected by the medical provider.
What is important is that a woman can decide what is best for her. Every baby is different and every childbirth is different and the woman is the one who has to do it.

Also, let us not forget, whatever way a childbirth is done; A woman is bringing new life to this earth. Literally and figuratively. I think we should always respect and acknowledge this manifestation of beauty.          

My little niece Dani Isabella, born on the 17th of June 2020.
*It could be that this article is updated from time to time.

24baby. (z.d.). IVF en ICSI vruchtbaarheidsbehandelingen [Illustration]. Geraadpleegd van https://www.24baby.nl/zwanger-worden/zwanger-worden-lukt-niet/ivf-icsi/

Cleveland Clinic. (n.d.). Fetal development: Month-By-Month Stages of Pregnancy. Geraadpleegd op 1 juli 2020, van https://my.clevelandclinic.org/health/articles/7247-fetal-development-stages-of-growth#:%7E:text=At%20about%206%20weeks%2C%20your,fetus%20instead%20of%20an%20embryo.

Daley, K. (2019, 25 juni). How pregnancy hormones affect your body in each trimester. Geraadpleegd op 1 juli 2020, van https://www.todaysparent.com/pregnancy/pregnancy-health/how-pregnancy-hormones-affect-your-body-in-each-trimester/

Galan, R. N. N. (2017, 12 oktober). Facts about sperm health and lifespan. Geraadpleegd op 8 juli 2020, van https://www.medicalnewstoday.com/articles/319669

IVF. (2016). [foto]. Geraadpleegd van https://www.google.com/search?q=IVF&rlz=1CAVHDQ_enNL786NL795&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjL16ukj8HqAhVEqHEKHY4yDfUQ_AUoAXoECA8QAw&biw=1807&bih=898#imgrc=QL-J4gYpJWjrHM&imgdii=6EBFZZ_yy-L4NM

Khan Academy. (2015). Egg meets sperm. Geraadpleegd op 1 juli 2020, van https://www.khanacademy.org/test-prep/mcat/cells/embryology/a/egg-meets-sperm

Jukic, A. M. Z., Weinberg, C. R., Wilcox, A. J., McConnaughey, D. R., Hornsby, P., & Baird, D. D. (2007). Accuracy of Reporting of Menstrual Cycle Length. American Journal of Epidemiology, 167(1), 26. Geraadpleegd van https://academic.oup.com/aje/article/167/1/25/185921

National Geographic. (2018, 20 december). Pregnancy 101 | National Geographic [Videobestand]. Geraadpleegd van https://www.youtube.com/watch?v=XEfnq4Q4bfk

Nature videos. (2018, 4 juli). Building a baby: The first two weeks [Videobestand]. Geraadpleegd van https://www.youtube.com/watch?v=9AX1XwKCYQE

NHS website. (2018, 24 september). What is the placenta? Geraadpleegd op 1 juli 2020, van https://www.nhs.uk/common-health-questions/pregnancy/what-is-the-placenta/#:%7E:text=The%20placenta%20is%20an%20organ,can’t%20perform%20for%20itself.

Nucleus medical media. (2013, 31 januari). Fertilization [Videobestand]. Geraadpleegd van https://www.youtube.com/watch?v=_5OvgQW6FG4

The Royal Women’s Hospital. (z.d.). Ovulation. Geraadpleegd op 8 juli 2020, van https://www.thewomens.org.au/health-information/fertility-information/getting-pregnant/ovulation-and-conception#:%7E:text=A%20step%2Dby%2Dstep%20guide%20to%20conception,woman%20is%20to%20become%20pregnant.

SCOTT, K. D., KLAUS, P. H., & KLAUS, M. H. (1999). The Obstetrical and Postpartum Benefits of Continuous Support during Childbirth. Journal of Women’s Health & Gender-Based Medicine, 8(10), 1257–1264. https://doi.org/10.1089/jwh.1.1999.8.1257

Sense. (n.d.). Sense.info. Geraadpleegd op 1 juli 2020, van https://sense.info/nl/ontdek-je-lichaam/meisjeslichaam/menstruatie/vruchtbaarheids-cyclus

Sex, Explained | Netflix Official Site. (2020a, 4 februari). Childbirth, Explained [Videobestand]. Geraadpleegd van https://www.netflix.com/watch/81062197?trackId=14170289&tctx=0%2C4%2C1217c216-43ae-45a9-a4a6-e67066cd615b-65476509%2Cb48f61c1-c8dc-4713-9df0-69dbbae7a52b_32857241X3XX1594157159149%2Cb48f61c1-c8dc-4713-9df0-69dbbae7a52b_ROOT%2C

Sex, Explained | Netflix Official Site. (2020, 4 februari). Fertility, Explained [Videobestand]. Geraadpleegd van https://www.netflix.com/watch/81062196?trackId=14170286&tctx=2%2C1%2C50b90f26-a4fa-4614-a102-38ab3d989ce1-547344392%2C6fa16ee1-caac-4025-b541-dfd211088e9b_15400151X3XX1594122976804%2C6fa16ee1-caac-4025-b541-dfd211088e9b_ROOT%2C

Tonei, V. (2019). Mother’s mental health after childbirth: Does the delivery method matter? Journal of Health Economics, 63, 182–196. https://doi.org/10.1016/j.jhealeco.2018.11.006

World Health Organization. (2007, 13 juni). WHO | Chapter 3. Geraadpleegd op 28 juni 2020, van https://www.who.int/whr/2005/chapter3/en/index3.html 

Published by Vincent Donders

Groot muziekliefhebber en erg geïnteresseerd in wetenschap en educatie.

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