The lungs begin producing surfactant
Baby this week: about 30 cm — head to heel · about 600 g
≈ 30 cm — about the size of an ear of corn
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- The lungs start producing surfactant, a substance needed for the air sacs to expand after birth
- Facial features are fully formed, though the fetus will keep filling out
- This week is often described as a threshold of viability, meaning survival outside the womb becomes possible with intensive medical care, though outcomes vary a great deal at this stage
- Taste buds are functioning, and the fetus may respond to different flavors in amniotic fluid
Your body this week
- The top of the uterus (fundus) is now a little above the belly button; from here, its height in centimetres roughly matches the number of weeks.
- A glucose screening test for gestational diabetes is often scheduled around this time
This week's tip: If your provider recommends a glucose screening test, ask about the preparation involved so you know what to expect.
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.