Your baby's development during pregnancy – week by week
Pregnancy is one long, amazing journey – both for you and for the little life growing inside you. It may feel almost unreal at first, but week by week, small (and big!) changes take place, which ultimately lead to you holding your baby in your arms. Here is an overview of the baby's development during pregnancy – from the first cell division to the scent of a newborn on your chest.
First trimester (weeks 1–12)
Fetal development in the first 12 weeks is all about formation. All organs, the nervous system, and blood vessels begin to develop in what we call the embryonic phase.
- As early as around week 5, the heart begins to beat.
- In weeks 7–8, the arms, legs, fingers, and facial features are formed.
- By week 10, all organs have been formed – and from now on, the little creature is called a fetus.
- In week 12, the fetus is about 5–6 cm long, and many choose to share the news with the world.
Second trimester (weeks 13–27)
Now the body begins to grow rapidly, and you will often feel a new calmness in your body – and perhaps also the first little kicks.
- In weeks 14–16, the fetus begins to be able to make facial expressions, drink amniotic fluid, and urinate.
- Around weeks 18–20, you can often feel the first clear signs of life – and at the anomaly scan in weeks 19–21, you can see all the little details.
- In weeks 23–24, the skin begins to become less transparent and the baby takes on a more “baby-like” shape. The lungs and nervous system are developing intensively.
- In weeks 25–27, the baby reacts to sound and light – and can recognize your voice.
Third trimester (weeks 28–40+)
Now it's mostly about growth and maturation. The baby is getting bigger, stronger, and more aware – and you are approaching the finish line.
- In weeks 28–32, the baby gains weight rapidly and develops a layer of fat that helps regulate its temperature. Its eyes open and sleep patterns begin to form.
- In weeks 33–36, the baby usually lies with its head down and practices breathing. Lung maturation continues.
- From week 37, the baby is physiologically fully developed and ready for life outside the womb – but continues to grow and mature a little more.
- In week 40 (or thereabouts), the big moment arrives. When your baby is ready and your body cooperates, labor begins – and you finally get to hold your baby in your arms.
