Some of the most important development in your baby happens in week four. The neural tube forms now, and this will become the spine and brain. Needless to say, this is an essential part of our bodies and how this tube forms will determine much of your baby’s development in the coming months.

The next part of your baby’s development is that it divides into layers. These will then form the bones, organs, skin, and features such the eyes and mouth. In the middle layer, the heart and circulatory system are the first to form as microscopic vessels. The digestive system is the next to begin development.

The embryo doesn’t yet look like a human as there is no head or limbs formed. If you could see the tiny embryo, you would notice that it looks more like a comma than anything else.

Along with the neural tube, the vitelline duct forms at this stage. This is basically a simpler version of the placenta and serves to supply the embryo with nourishment as it grows. This duct will develop into the placenta and umbilical cord.

In week four, if you go for an ultrasound, it’s more likely that you will only see the vitelline duct and not the actual baby. This is because the embryo is so small that it’s almost impossible to pick it up even with the best scanning equipment. The embryo at this stage is smaller than a grain of rice, about 2mm only

How mom is feeling

By week four, you should be feeling a few changes happening in your body. Your levels of hCG (the pregnancy hormone) are rapidly increasing and so are your levels of progesterone. These two hormones are responsible for the majority of the early symptoms of pregnancy.

You’ll find that you likely become a lot more sensitive to smells and tastes, even of foods and drinks that you usually like. This then leads to nausea that is so common in the first trimester.

In some cases, women don’t notice that they are pregnant or that there have been any changes in their body at this stage. However, the symptoms will start to intensify as the pregnancy progresses. Once your menstruation is late, you’ll probably start to wonder if you are pregnant and can take a test to confirm the theory.

Signs and symptoms

There are several symptoms of early pregnancy but the most important sign to look out for is late menstruation. All of the other symptoms mean nothing until you are at least five days late and can take a test to confirm what you are suspecting.

The very first sign of pregnancy that you may experience is that of implantation bleeding. Only about 10% of women experience this, and most of these women don’t realize what it is. Basically, when the embryo implants into the endometrium, a small piece of this lining can break off and exit through the vagina. It will come out as spotting and the blood will be dark and old. Most women who see this will think the blood is the early onset of menstruation or just some spotting before their menstruation starts properly.

After implantation occurs, your body starts to produce hCG and higher levels of progesterone. These hormones can cause changes in your body that are similar to those of PMS. These symptoms include a hardening in the lower abdomen, as well as tenderness in the breasts. Not all women will experience these symptoms at this stage, and may only start to notice changes much later on. This is all quite normal because it depends on how your body responds to higher levels of hormones.

External factors

As soon as you discover that you are pregnant, it’s important to start proper prenatal care. Folic acid is essential at this early stage because it helps to prevent malformation of your baby’s neural tube.

It is possible at this early stage for your body to reject the embryo due to a variety of reasons. The most common is that there is a defect or malformation occurring in the development. If you experience any bleeding or spotting from the vagina, it’s important to contact your doctor immediately. They will be able to diagnose what is causing this and if there is a way to save your pregnancy.

Readers’ questions:

What does the fetus look like at four weeks of gestation?

At this stage, the baby is still so small that it usually can’t be seen on an ultrasound. It’s smaller than a grain of rice, roughly 2mm. The embryo also doesn’t yet look like a human as there are no limbs or much shape to the body.

What should my uterus look like at four weeks pregnant?

Your uterus can become slightly swollen and harden due to the increase in progesterone in your body. The swelling has nothing to do with the actual baby growing inside of you because it is still far too small to have any impact.

What symptoms will I feel at four weeks pregnant?

The main sign of pregnancy that you’ll experience now is that of menstrual delay. This is usually the first sign that most women notice and connect with the thought that they might be pregnant. You might also experience symptoms such as nausea, dizziness, a hardening of the lower abdomen and sensitivity and pain in your breasts.