Pregnancy week by week
What's developing at each week of the first trimester. Weeks are counted the way doctors count them, from the first day of your last period.
Not sure which week you're in? Use the pregnancy week calculator.
4 weeks pregnant
The tiny ball of cells has just implanted in the wall of the uterus.
5 weeks pregnant
The embryonic period begins, and the brain, spinal cord and heart start to develop.
6 weeks pregnant
Buds that will become arms and legs appear, and cardiac activity may be seen on ultrasound.
7 weeks pregnant
The heart beats at a regular rhythm and blood pumps through the main vessels.
8 weeks pregnant
The arms and legs are longer and the hands and feet are starting to form.
9 weeks pregnant
All of the essential organs have begun to grow.
10 weeks pregnant
The embryo becomes a fetus, and the heartbeat may be heard with a handheld Doppler.
11 weeks pregnant
The face is well formed and the nails are starting to grow.
12 weeks pregnant
The baby can make a fist and tooth buds are appearing.
13 weeks pregnant
The first trimester ends and the structures for hearing begin to develop.
For weeks 14 to 40, see fetal development week by week.
Sources
- MedlinePlus. Fetal development.
- ACOG. How your fetus grows during pregnancy; Abortion language guide.
- ACOG. Methods for estimating the due date.
“God is our refuge and strength, a very present help in trouble.”