How many months is 42 weeks pregnant?

42 weeks pregnant puts you in month 9 of pregnancy. Pregnancies that go past 40 weeks are still counted as month 9. Providers count in weeks; months are approximate.

How big is the baby at 42 weeks?

At 42 weeks, the baby is about the size of a watermelon, roughly 51.7 cm long and around 3685 g. That is an average; healthy babies vary.

Is 42 weeks pregnant dangerous?

Problems happen in only a small number of post-term pregnancies, and most end with a healthy baby. But some risks do go up. They include a very large baby, less fluid around the baby, and the baby breathing in its first poo (meconium), which can cause breathing problems. Rarely, stillbirth can happen. For you, the chance of a caesarean or assisted birth, infection and heavy bleeding after birth also rises. That's why extra checks or induction are offered.

What causes a baby to be overdue?

Doctors don't know the exact cause. Some things make a post-term pregnancy more likely: this being your first baby, carrying a boy, having had a post-term pregnancy before, and obesity. How the due date was set also matters. An early dating scan gives the most accurate date, and once a due date has been chosen, later scans don't change it. How common it is varies from place to place, partly because care practices differ. In the US in 2011, 5.5% of pregnancies were post-term.

What happens at 42 weeks with no signs of labour?

Your midwife or doctor will talk with you again about induction. If you'd rather wait, you'll be offered extra monitoring. Labour can still start on its own, and the usual signs apply: contractions that come regularly and get stronger, a show, backache, or your waters breaking. Call your maternity unit when contractions come every 5 minutes or more often. Don't wait if your waters break, you notice bleeding, or your baby moves less: call right away.

What does a baby born at 42 weeks look like?

Babies born late often have red, dry, cracked or peeling skin. This is because the greasy coating called vernix was absorbed before birth. The top layer peels off by itself within a few days, so there's no need for creams or lotions. Plain water is best for washing in the first month. Some post-term babies also have long nails, lots of hair and a long, lean body with thin, wrinkled skin. Doctors call this postmaturity syndrome.

42 Weeks Pregnant

At 42 weeks pregnant, you are two weeks past your due date. From this point, a pregnancy is called post-term. Getting this far is uncommon. In hospital data from England, only 0.9% of labours that started on their own began at 42 weeks or later. Many people at this point have already been offered an induction, and some have chosen to wait for labour instead. It's your choice, and you can talk it through again at every check. This page covers the extra checks offered from 42 weeks and your options if you'd rather not be induced. It also explains what happens if an induction doesn't start labour, and what a baby born at 42 weeks may look like.

What trimester is 42 weeks?

Week 42 is in the third trimester, which runs from week 28 until birth. That is 2 weeks past the 40-week due date.

Week 42 — third trimester, month 9; you're 2 weeks past your due date.
Baby's size — about a watermelon, ~51.7 cm.

Not sure it's 42 weeks? Try our due date calculator.

★ Post-term begins at 42 weeks.

How big is your baby at 42 weeks?

Size of a

watermelon

Length, head to heel

~51.7 cm

Weight

~3685 g

Up from a pumpkin last week to a watermelon now.

Baby development at week 42

Few pregnancies reach 42 weeks, partly because induction is usually offered from 41 weeks. From 42 weeks a pregnancy is called post-term, and the placenta may work less well over time. The baby is fully developed and simply waiting. Close monitoring of the baby's wellbeing continues, and your team will guide the safest path to delivery. About the size of a watermelon.

Monitoring after 42 weeks

If you decide not to be induced, UK guidance says you should be offered extra checks on your baby from 42 weeks. These might be a heart-rate trace, called a CTG, twice a week, plus an ultrasound scan to measure the deepest pool of fluid around your baby. In the US, your provider may also suggest a contraction stress test. It checks how your baby's heart rate responds when your uterus tightens, which may be brought on with oxytocin through a drip.

Low fluid matters because it can let the umbilical cord get pinched, which can reduce the oxygen your baby gets. These checks are useful, but they have limits. Each one shows how your baby is doing at that moment. It can't reliably predict what will happen after the check, or prevent every problem. That's why it still matters to notice your baby's movements every day, and to call straight away if they slow down or change.

Your body at 42 weeks

Labour signs may finally arrive
Significant physical discomfort
Increased monitoring appointments
Anticipation and fatigue

If you don't want to be induced

Induction is an offer, and saying no is your right. If you choose to wait, your midwife or doctor should talk through your options with you, such as waiting for labour with extra monitoring, or a planned caesarean. They should record your decision in your notes. You can change your mind at any later check. It helps to know the trade-off: some risks for the baby may keep rising over time after 41 weeks, even though most babies born this late are healthy.

While you wait, call your maternity unit at once if your baby moves less, your waters break, or you have any bleeding. If your waters break and labour doesn't start within 24 hours, you'll usually be offered an induction, because the risk of infection goes up. Until then, take your temperature every 4 hours while you're awake. Tell your midwife if it's raised, which usually means above 37.5C.

Tips for week 42

Induction is typically recommended by 42 weeks for safety
Keep all monitoring appointments
Discuss the delivery plan thoroughly with your care team

42 Weeks Pregnant: your questions

What trimester is 42 weeks?: Week 42 is in the third trimester, which runs from week 28 until birth. That is 2 weeks past the 40-week due date.
How many months is 42 weeks pregnant?: 42 weeks pregnant puts you in month 9 of pregnancy. Pregnancies that go past 40 weeks are still counted as month 9. Providers count in weeks; months are approximate.
How big is the baby at 42 weeks?: At 42 weeks, the baby is about the size of a watermelon, roughly 51.7 cm long and around 3685 g. That is an average; healthy babies vary.
Is 42 weeks pregnant dangerous?: Problems happen in only a small number of post-term pregnancies, and most end with a healthy baby. But some risks do go up. They include a very large baby, less fluid around the baby, and the baby breathing in its first poo (meconium), which can cause breathing problems. Rarely, stillbirth can happen. For you, the chance of a caesarean or assisted birth, infection and heavy bleeding after birth also rises. That's why extra checks or induction are offered.
What causes a baby to be overdue?: Doctors don't know the exact cause. Some things make a post-term pregnancy more likely: this being your first baby, carrying a boy, having had a post-term pregnancy before, and obesity. How the due date was set also matters. An early dating scan gives the most accurate date, and once a due date has been chosen, later scans don't change it. How common it is varies from place to place, partly because care practices differ. In the US in 2011, 5.5% of pregnancies were post-term.
What happens at 42 weeks with no signs of labour?: Your midwife or doctor will talk with you again about induction. If you'd rather wait, you'll be offered extra monitoring. Labour can still start on its own, and the usual signs apply: contractions that come regularly and get stronger, a show, backache, or your waters breaking. Call your maternity unit when contractions come every 5 minutes or more often. Don't wait if your waters break, you notice bleeding, or your baby moves less: call right away.
What does a baby born at 42 weeks look like?: Babies born late often have red, dry, cracked or peeling skin. This is because the greasy coating called vernix was absorbed before birth. The top layer peels off by itself within a few days, so there's no need for creams or lotions. Plain water is best for washing in the first month. Some post-term babies also have long nails, lots of hair and a long, lean body with thin, wrinkled skin. Doctors call this postmaturity syndrome.
What happens if an induction doesn't start labour?: Induction doesn't always work, and it often takes many hours. If labour hasn't started, your midwife and obstetrician will check how you are and how your baby is doing, including a heart-rate trace (CTG). Then they'll talk through the options with you. These may include trying another method of induction, waiting a few hours and checking again, or having a caesarean. You'll be part of the decision.

Useful at week 42

Gestational age calculator — count your exact weeks and days past your due date
Pregnancy weeks to months — 42 weeks in months — the full chart
Baby age calculator — track your newborn's age in weeks and months
Period after pregnancy — when periods usually come back after birth
Breastfeeding and periods — how feeding affects when your cycle returns

← All weeks: the full pregnancy week-by-week guide

Sources

Checked against the following public guidance on October 2, 2026. Advice can differ between countries; your doctor, nurse or midwife can apply it to you.