Muscles and lungs continue to mature quickly
Baby this week: about 38.7 cm — head to heel · about 1.15 kg
≈ 38.7 cm — about the size of a butternut squash
Illustration enlarged for clarity — the amber marker shows true relative size
Your baby this week
- Muscles and lungs continue to mature, though the lungs still need more time
- The head is growing to keep pace with the rapidly developing brain
- Bones are fully formed but still soft and flexible
- The fetus can now regulate its body temperature somewhat, though it still relies heavily on the womb's environment
Your body this week
- Backaches and pelvic pressure often increase as the baby's weight grows
- Frequent bathroom trips return as the uterus presses on the bladder again
This week's tip: Kegel exercises can help support pelvic floor muscles as they carry increasing weight in the coming weeks.
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.