The third trimester begins
Baby this week: about 37.5 cm — head to heel · about 1 kg
≈ 37.5 cm — about the size of a head of cabbage
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- The third trimester begins this week
- Eyes can now open and close, and blink reflexively
- The fetus is gaining weight steadily as fat stores build up
- Brain wave patterns show characteristics of active sleep, similar to dreaming
Your body this week
- Appointments often become more frequent from this point on, typically moving to every two weeks
- Shortness of breath can occur more easily as the uterus takes up more space
This week's tip: Get to know your baby's usual pattern of movements; there is no set number to count. If your baby moves less than usual, you cannot feel it moving, or the pattern changes, contact your maternity unit now, even at night, and do not wait until the next day or use a home Doppler to check.
When to get help now
Contact your maternity unit now, even at night, if your baby is moving less than usual or the pattern has changed, you have any vaginal bleeding, fluid leaks from your vagina, you have regular or painful contractions before 37 weeks, or you have a severe headache, vision changes, pain just below the ribs or sudden swelling of the face, hands or feet. Do not wait until the next day.
Sizes and milestones are typical ranges — every pregnancy runs on its own clock. Educational content; your prenatal care team's guidance always comes first.