The first trimester of pregnancy – what to expect

First trimester

Congratulations on your pregnancy! If you have just found out that you’re pregnant, you are most likely in the first trimester, which means the first 13 weeks of your pregnancy. During this time, all kinds of changes take place in and with your body. This is the time when your baby grows and develops at a dramatic rate – and this does not go unnoticed. You feel fatigue, you may be nauseous and your hormones are in overdrive.

Hormones during the first trimester

Hormones during the first trimester

The first trimester of pregnancy is a crucial time because this is when your baby’s organs and systems are formed. This development is closely regulated by different hormones that send essential signals and instructions to the embryo’s organs. So, it’s not surprising that your hormones can get completely out of whack during the first trimester.

The hCG hormone

The hCG hormone

The most well-known hormone is hCG. This hormone is what results in a positive pregnancy test. The hormone hCG plays a major role during the first trimester of pregnancy. It is produced by the placenta and stimulates the production of other hormones. It also plays a role in the development of the placenta and your baby’s blood vessels. Apart from fluctuating hormones, you can also experience all kinds of other symptoms and discomforts during the first trimester.

Symptoms in the first trimester of pregnancy

The first trimester of your pregnancy is a time when you may experience a lot of different discomforts. We’ve put together a list of the most common ones:



A lot of changes are taking place in your body at this time. All of your energy is directed towards producing the placenta and the development of the baby in your belly. And then there’s all the hormones raging through your body. So, it’s not surprising that you feel extremely tired during this time.

Just when you thought that you knew what it felt like to be exhausted, the fatigue experienced during the first trimester kicks this up a notch or two.


Abdominal pain

At the very start of pregnancy, implantation can cause pain in your lower abdomen. In the first trimester, your body is also preparing for a growing baby. Your baby will be growing and developing – and your uterus along with it. This can cause cramping in your abdominal area and sometimes also in your lower back. The sensation is similar to menstrual cramps. You may also experience gastrointestinal issues during the first trimester. The hormone progesterone causes your intestines to slow down, which can lead to stomach aches and constipation.



Nausea is a common discomfort during the first trimester. Many women experience nausea in the morning, which is why it is often referred to as morning sickness. But this nausea can also last all day long. It is caused by the hormones in your body. The hormone hCG that you produce at a record rate during the first trimester is the culprit and peaks at around 11 weeks. During the second trimester, hCG levels start dropping and the nausea usually also subsides.


Lower back pain

Like stomach aches, you may also experience pain in your lower back during the first trimester. Most back pain is due to the physical changes taking place in the body during pregnancy, such as hormonal changes and changes to your posture.

Your baby during the first trimester

Your baby during the first trimester

The first trimester of pregnancy obviously starts at conception and the subsequent implantation of the fertilized egg. This egg then grows into an embryo. During the first 12 weeks, the embryo in your belly develops into a fetus of around 6.5 cm (2.6 inches).

At around week six, your baby’s heart starts beating and he or she has a primitive circulatory system. Then your baby develops bones, brain and spinal cord and other vital organs start growing and developing. Whether your baby is a boy or a girl is determined at conception, but the external genitals are visible from week 12.

Announcing your pregnancy

Announcing your pregnancy

Since the risk of a miscarriage is significantly lower after the twelfth week of pregnancy, this is often the time when most people announce their pregnancy. It’s a special moment and there are also lots of fun and original ways to announce the news. You can also announce your pregnancy earlier, of course. Simply do what feels right for you (and your partner)!

What to keep in mind

During the first trimester of pregnancy

Being pregnant is a very special time in your life. After all, a child is growing in your belly! As can be expected, there are a number of things to keep in mind during this process that may not be good for your baby or its development. There are a number of foods you should not eat, for instance, and not only during the first trimester but throughout your entire pregnancy.

Obviously, you should not drink alcohol, it is not a good idea to eat raw eggs, meat or fish, and there are other foods that you should either avoid or only eat occasionally.

Also keep in mind that it is not recommended to use a sauna during the first three months, i.e. the first trimester of your pregnancy. The high temperature can negatively affect your baby’s development. Using a jacuzzi is also not recommended for the same reason.


To-do’s during the first trimester of pregnancy

Choose a doctor (OB-GYN). Also make sure to find out what your insurance covers.
Schedule a prenatal visit as soon as you find out that you are pregnant. During the first appointment, the doctor will ask about your medical history and that of the baby’s father. You will also be asked about whether you smoke and your lifestyle in general. Your due date will be determined and urine and blood tests may be done.

  • Make sure you schedule enough prenatal visits, so that your blood pressure and your baby’s heartbeat can be monitored.
  • Read about the different tests that are available and decide which ones you want to do in relation to genetic abnormalities.
  • From the start of your pregnancy – and preferably even earlier – make sure to take folic acid every day for at least the first three months, which will help with the development of your baby’s brain and spinal cord.