Third trimester
42 weeks pregnant
Your baby is about the size of a watermelon
By Clever Mum Parenting · Parenting guides
How big is the baby at 42 weeks pregnant?
At 42 weeks pregnant, your baby is about the size of a watermelon, roughly 51.7cm and around 3700g. Fewer than 1 in 10 pregnancies reach 42 weeks. The baby continues to grow and the placenta is monitored closely, because it gradually becomes less efficient past this point. These are typical averages — your midwife's measurements are the ones that matter for your pregnancy.
What might you feel at 42 weeks?
Most people at 42 weeks notice some mix of the symptoms below — and plenty notice none of them. By 42 weeks you'll usually have been offered induction, since the risk of complications rises slowly beyond this stage. If you decline, you'll be offered extra monitoring (CTG and scans) instead — the choice remains yours. None of this is a diagnosis; contact your midwife if something worries you.
Common symptoms this week
- Very overdue (fewer than 1 in 10 get here)
- Daily or alternate-day monitoring
- Every tightening scrutinised
Symptom lists are typical, never exhaustive — and having none of them is normal too.
What should you do at 42 weeks pregnant?
The useful job this week is practical, not medical. Talk through the induction process with your midwife so you know what to expect — pessary or gel, breaking the waters, and a hormone drip are the usual steps, in that order and only as needed. Pair it with the NHS week-by-week guide if you want a second description of the same stage.
Week 42 checklist
- Attend all monitoring appointments (CTG traces and fluid scans)
- Confirm your induction date and what to bring
- Rest — the finish line is genuinely days away
What else is useful at 42 weeks?
Use the week page for size and symptoms; use the guides below for the decisions that actually sit in this window — pay, packing, car seats, labour signs.
42 weeks pregnant: common questions
Is it safe to go past 42 weeks pregnant?
Risks to the baby rise slowly but measurably beyond 42 weeks as the placenta ages, which is why UK guidance recommends induction by then and close monitoring (CTG and fluid checks) for anyone who declines. Whatever you choose, it's made with your team — consent remains yours throughout.
How big is my baby at 42 weeks pregnant?
At 42 weeks, your baby is approximately the size of a watermelon, about 51.7cm and around 3700g. These are approximate averages — every baby grows at its own pace.
What's happening at 42 weeks pregnant?
Fewer than 1 in 10 pregnancies reach 42 weeks. The baby continues to grow and the placenta is monitored closely, because it gradually becomes less efficient past this point. For you: by 42 weeks you'll usually have been offered induction, since the risk of complications rises slowly beyond this stage. if you decline, you'll be offered extra monitoring (ctg and scans) instead — the choice remains yours.
Which trimester is 42 weeks?
42 weeks pregnant is in the third trimester. The first trimester runs to the end of week 12, the second from weeks 13 to 26, and the third from week 27 to birth.
Sources & further reading
This is general information, not medical advice — every pregnancy is different. For anything that worries you, and for all your antenatal care, speak to your midwife or GP. If your baby's movements ever slow down or change, contact your maternity unit immediately, day or night. Reviewed August 2026.