Magnified image of uterus with ovary and egg follicles
Diagram of the uterus with ovaries and eggs. Image: Shutterstock

Pregnancy is scary and exciting all at once, especially if you’re experiencing it for the first time. And just like every other scary-and-exciting-at-the same-time thing, having a good understanding of what it entails can go a long way in alleviating any fears you have.

This series of articles will help you to better understand pregnancy, and what’s going on with you and your baby.

Getting pregnant

Although there are several ways to do it, the most common way that people get pregnant is through vaginal sex. Pregnancy occurs when one of your eggs is fertilised by a sperm and starts growing into a baby in your uterus.

Normal human pregnancies will last for 264 days. However, they are usually dated from the first day of the last menstrual cycle, which adds up to 280 days or 40 weeks. These weeks are divided into three trimesters of 13 weeks each.

The first trimester starts before you get pregnant. In the first two weeks, you’re not really pregnant since the sperm and the egg have not met yet. However, for calculation purposes, medical professionals have to count this fortnight.

Week 1 and 2

Your weeks are counted from the first day of your last period. Over week 1 and 2, your body is laying the groundwork for your next ovulation period. This process starts 14 days after the start of your last period.

The ovaries release a hormone called the luteinizing hormone (LH), which triggers the release of an egg that is ready to be fertilised. This egg then starts travelling up the fallopian tube. The entire process takes about six days and is referred to as the ovulation period. If the egg is not fertilised, it will be released out of your body as part of your period.

Over these first two weeks you may notice:

  • Your cervical mucus becomes clear, thin and stringy, almost like raw egg whites. This mucus, and its consistency, is what helps the sperm to travel towards the egg.
  • You may experience a change in basal temperature (lowest body temperature at rest). The temperature will reduce to its lowest then shoot up as soon as ovulation starts.
Sperm cell swimming towards mature egg cell
Sperm cell about to fertilise egg cell. Image: Shutterstock

Week 3

If a sperm meets your egg in your fallopian tubes and fertilises it, congratulations! Conception has occurred!

The sperm and egg will fuse to form a single cell called a zygote. This newly formed cell then forms a barrier to keep the other sperm cells out.

However, this cell doesn’t stay single for long. It starts dividing into two cells, then four, then eight and then to 16. When the zygote has 16 cells, it is called a morula. Keep in mind that at this point, the zygote is still microscopic and is not detectable by ultrasound.

What about twins? Well, unlike a single baby, the formation of twins is a little different, depending on the type of twins you’ll have conceived. For identical twins, the single zygote splits into two separate embryos. The time at which they split will determine whether or not they share the placenta, amnion (the membrane that becomes the amniotic sac) and chorion (the protective barrier around the amnion). If the zygote splits at an earlier stage, your twins will develop independently. If it splits towards the late blastocyst stage, they will share the placenta, amnion and chorion.

The conception of fraternal twins is also different and happens when two separate eggs are fertilised by two different sperm cells. They will then develop in your uterus, each with their own little bubble.

As the zygote (now morula) keeps dividing, it starts to roll down the fallopian tube as a ball of cells, heading to the uterus. This journey will take about five to six days. By the time it gets to your uterus, your baby will be about the size of a vanilla bean seed!

Within the third week, the cells will start to produce hCG (human chorionic gonadotropin). This is a hormone that tells your body that you’re pregnant. It will be transported throughout your body in your blood, and will also appear in your urine, meaning you will get positive results on a urine pregnancy test.

A morula or early stage embryo of cells
A morula is an early embryo consisting of cells. Image: Shutterstock

Here are some of the things you may notice in the third week:

  • A missed period. This is one of the most tell-tale signs of pregnancy. If you notice a missed period, it is a good time to get a pregnancy test done.
  • You might also experience unusual tiredness.
  • Moodiness. This is often the result of the change of hormone production in your body.
  • Breast tenderness. Your breasts will start to feel a little sore and tender, and your nipples may darken. This is because your body is getting ready to start making milk. This symptom may persist well into the fourth week of pregnancy.

If your pregnancy test comes back positive, here are a few things you can do to ensure the health and well-being of the baby:

  • You should start taking prenatal supplements with folate. These will help to reduce the chances of your baby having any neural tube, brain, and spinal cord defects. Consult your doctor about this and get your correct dosage.
  • Now would also be a good time to quit drinking and smoking. Tobacco use has adverse effects on your growing baby. It will increase your baby’s heart rate and may also increase the risk of stillbirth and miscarriage.
  • You should also adopt a healthy diet rich in iron, vitamin C, calcium and protein.

Week 4

By the beginning of the fourth week, your uterus is a flurry of activity. The zygote (morula) arrives at the uterus, and, at this point, it is called a blastocyst. The blastocyst then implants itself in your uterine wall, which becomes its new home where it will grow for the rest of your pregnancy.

Next, this ball of cells will split into two parts. One part will go on to form the embryo and the other half will form the placenta. The placenta is responsible for providing your baby with nourishment and carrying waste away while your baby is growing inside you. It will also take over the production of hCG.

By this point, your baby is the size of a poppy seed. It is still not necessary to have an ultrasound because the baby is so tiny and will only show up as a tiny dot, which is the gestational sac.

Medically accurate 3D rendering of a blastocyst
The morula becomes a blastocyst and implants itself in the uterine wall. Image: Shutterstock

Here are some of the symptoms to expect at four weeks pregnant:

  • Implantation bleeding. This happens when the blastocyst attaches itself to the uterine wall. This light spotting can be mistaken for menstrual blood but occurs earlier than your expected period would. However, if the bleeding feels abnormal or too much, you should consult your obstetrician or healthcare professional.
  • Your stomach may feel a little bloated due to an increase in progesterone (female sex hormone) production.
  • Nausea and/or vomiting. This can be attributed to the heightened sense of smell that comes with pregnancy, which is what 50-90% of pregnant women have to deal with, especially in the morning, hence the term morning sickness. However, a lot of pregnant women will have morning sickness throughout the day. Morning sickness typically drags out to the ninth week of pregnancy, then gradually gets better, generally disappearing altogether by the end of the second trimester.
  • Mood swings. Your body is producing a lot of hormones, which can make your moods switch wildly from time to time.
  • Mild cramping. You may feel some mild pain in your abdomen, but this is no cause for alarm. The cramping is as a result of the implantation.

As you make the lifestyle changes necessary to ensure your baby’s healthy development, this would also be a good time to find an obstetrician if you don’t already have one, and make an appointment for your first prenatal visit.

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