Close-up of a pregnant woman's stomach
© Love Matters | Rita Lino

Pregnancy week-by-week

A sperm fertilises an egg and about 40 weeks later, it's developed into a fully-grown baby, ready to be born. But in the meantime, what exactly is going on inside the womb?
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Fertilisation

You can get pregnant if you have intercourse with a man around the time you ovulate – from about five days before until one day after. When the man ejaculates inside your vagina, the sperm swims up the vagina through the cervix – the neck of the womb – through the womb, or uterus, to the fallopian tubes.

It takes the sperm about 10 hours to make this journey. If there’s an egg waiting in one of the fallopian tubes, the tiny sperm tries to burrow their way inside it. If one sperm gets inside the egg, it’s fertilised. The fertilised egg then sets off down the fallopian tube to the womb.

Week 1 of pregnancy

The fertilised egg cell starts dividing – at this stage, it’s called a zygote. After a few days of division, it becomes a ball of cells called a morula. You’d need very good eyes or a microscope to see it.

The blob of cells develops a hole in the middle full of fluid, at which point it gets another new name: blastocyst. First, it floats around the walls of the womb for a while. At this stage, it could still just get flushed out of your womb with your period, and you’d never know anything had happened. But then comes a crucial moment: if the womb accepts the blastocyst, and it nestles into the lining, you’re pregnant.

Even then, all sorts of things can go wrong in the early stages of pregnancy. You might notice nothing more than your period coming a couple of days late, when in fact you were nearly going to have a baby. It’s only called a miscarriage if it happens later on after you know you’re pregnant.

Week 2 of pregnancy

The pregnancy is now properly established. Inside the blastocyst, different groups of cells develop, which will eventually form the different parts of the baby. The inner cells will grow to become lungs, stomach and intestines, a middle layer will be muscles and bones, and an outer layer will form the nerves and skin.

It's time for the blastocyst to have another new name. It’s now an embryo. The end of the second week is about day 28 of your menstrual cycle – that means your period is due. And at this stage, depending on whether or not you wanted to get pregnant, you’re likely to start getting nervous and worried, or hopeful and excited. Because your period is late.

From a couple of days before your period was due, pregnancy hormone starts getting into your urine. So as soon as your period is late, you can do a pregnancy test.

Week 3 of pregnancy

The bundle of cells starts developing the first signs of the different parts of the body – the brain and heart start to grow.

Weeks 4 to 8 of pregnancy

The heart starts beating, and arms, legs, eyes and ears start to form. Nipples appear, and the kidneys start producing urine. The embryo starts moving. By the end of week eight, the embryo is about the size of a small grape – about 13mm. And once again it’s time for a name change: the embryo is now called a foetus.

Weeks 9 to 12 of pregnancy

The foetus now develops a recognisable human face. Its arms and legs are properly formed and it can make its hands into a fist. What’s more, the foetus can even make sounds – even though it’s still no longer than your thumb.

Twelve weeks marks the end of what’s known as the first trimester, the first third of the pregnancy. Miscarriages are much more likely to happen in the first twelve weeks, so women sometimes prefer to wait to this point before telling everyone they know that they’re pregnant. In some countries where abortion is allowed, you can’t have the pregnancy terminated after this point, or only in special circumstances.

Weeks 13 to 19 of pregnancy

The foetus starts moving around and making sucking movements with its mouth. By week 19 the baby is waking and sleeping and can hear. It’s about 12 to 15cm long, so would still fit in the palm of your hand.

Weeks 20 to 24 of pregnancy

Butterflies fluttering inside you, or bubbles – that’s how many women describe feeling the foetus moving inside them for the first time. It usually happens around this time of the pregnancy. However, with a first baby, you may not feel it until 25 weeks – and with a second baby, it can be as early as 16 weeks.

Apart from swimming around, the foetus is now growing eyebrows and eyelashes, and nails on its fingers and toes. The senses of taste and touch are developing, and the eyes are properly developed too. With a lot of medical care, foetuses born at 24 weeks can sometimes survive.

Weeks 25 to 28 of pregnancy

The brain is growing fast and by week 28 the lungs are properly developed, so if the baby is born at this stage it has a good chance of survival. Week 28 is the end of the second trimester, the middle third of the pregnancy.

Weeks 29 to 40 of pregnancy

In this last stretch of the pregnancy, the third trimester, the foetus grows fast and puts on weight, getting ready for life outside the womb. It starts ‘breathing’ the amniotic fluid inside the womb.

The foetus hasn’t got much room to move around anymore, but it can give some impressive kicks and you can see it moving from the outside. Around week 36, all being well, it swivels around so its head is pointing downwards ready for the birth.

The due date

People usually say a pregnancy lasts nine months. And based on the first day of your last period, you’re usually given a ‘due date’ when your baby is supposed to be born. But in fact, most births happen anywhere between about 37 and 42 weeks. So within this period, you can’t really say the birth is ‘early’ or ‘late’.

Anyway, at some point around 40 weeks, the big moment arrives. Having been a zygote, a morula, a blastocyst, and an embryo, the foetus now has its last official name change of the pregnancy: it’s a baby. After that, the name is up to you!

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Comments

Hey Sophia, have you discussed this with your health care provider or midwife? The weight of you baby can be influenced by a number of things. Do discuss this with your health care provider as part of monitoring your health and that of your baby.

Hey Tina, are you past your due date? It is normal to experience some pain or cramping during pregnancy as the baby grows and as the uterus stretches to accommodate the growth of the baby. It is important however, that you discuss this with your doctor or midwife especially if the pain is server than before, since there are a number of reasons that may causes such pain. They will be able to advice you appropriately. We wish you all the best. 

Hi Christabel, one should wait to take a pregnancy test until the week after they have missed their period for the most accurate result. If one doesn't wish to wait until they have missed their period, they should then wait for at least one to two weeks after they had sex. The urine test can detect pregnancy after 10 days. The blood test which can be done at a laboratory or health facility, is able to detect pregnancy after a week. Have a look at the following article for additional information;- https://lovemattersafrica.com/pregnancy/unsure-about-being-pregnant/am-i-pregnant

I saw my period 27-09-19 and after one week of having like two/three times in a week I started feeling my stomach paining me and now what am feeling some times is cool,weakness,sleepery,and some times movement in my stomach. what could that be please educate me on it
Am experiencing this problem for 8 month now i feel movement in my womb and heavy but sees my period every month some time ifeel like i am pregnant but i don't know what is happening

Hello Asmau, thank you for reaching out to us. Are there any other symptoms you are experiencing that could indicate that you are indeed pregnant e.g. Swollen tummy? Morning sickness? Enlarged and tender breasts? Nausea from certain smells and tastes? If you have been experiencing these symptoms then it is extremely important that you VISIT A DICTOR IMMEDIATELY, lest you risk putting your potentially unborn child and yourself at extreme risk my dear. 

Hi bimbo, thank you for reaching out to us and asking a great question. Your due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (assuming a 28 day cycle). Note that your menstrual period and ovulation are counted as the first two weeks of pregnancy. If you deliver on your due date, your baby is actually only 38 weeks old, not 40.

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