Your baby begins its life as a fertilised egg which develops into an embryo in the first 8 weeks after conception. After the first 8 weeks, the embryo is referred to as the foetus, which means offspring.

The foetus grows steadily in the womb during the subsequent weeks, developing limbs, facial features and organs, as well as gaining weight and length. At week 37, the foetus is considered full term, though the actual due date is at week 40.

“At 37 weeks, all organs are developed and the foetus is ready to make an appearance at any time,” says Dr Hong Sze Ching, Visiting Consultant, Department of ​Obstetrics and Gynaecology, KK Women’s and Children’s Hospital (KKH), a member of the SingHealth group.

First trimester (Pregnancy weeks 1-12)

The foetus’ organs, such as the brain, heart, lungs and intestines begin to develop in pregnancy week 5. Growth accelerates in week 6 when the foetus becomes viable, that is the heartbeat can be seen on a transvaginal ultrasound scan. This is the most important milestone of the first trimester.

By week 6, arms and legs begin to form and by week 7, the head develops. By week 8 and 9, the fingers and toes begin to form and the eyes, nose and ears become visible. By week 10, the neck develops. The genitals develop in week 11 and in week 12, the fingernails begin to form. At the end of the first trimester of pregnancy, the foetus typically will be just over 6 cm long and weigh about 14g.

Read on for a summary of what happens in the second and third trimester​.

Read here for a complete pregnancy week by week guide by KKH.

Ref: M19