Pregnancy week by week

Discover how your baby grows and how your body changes in every week of pregnancy. Pregnancy lasts 40 weeks divided into three trimesters, and each week brings its own signs.

Weeks are counted from your last menstrual period, not from when you took a test or first noticed something. Not sure which week you're in? Use the calculator below.

First trimester

Pregnancy Week 1: How the Weeks Are Counted

Pregnancy week 1 starts on the first day of your last period. I'll explain how pregnancy weeks are counted and why there's no baby yet at this point.

Pregnancy Week 2: Ovulation and Your Fertile Days

In pregnancy week 2 you ovulate. I'll explain when your fertile days are and what happens in this stage before conception.

Pregnancy Week 3: Fertilisation and Implantation

In pregnancy week 3, fertilisation and implantation happen. I'll explain what goes on in your body and why the test can still be negative.

Pregnancy Week 4: Symptoms, Tests and Baby Size

Find out what happens in pregnancy week 4: when to take the test, the first symptoms, the baby's size and the signs that everything is going well.

Every week we explain your baby's development, the most common symptoms and practical tips. If you have any questions about your pregnancy, remember this content is for information only: always consult your doctor.