At 40 weeks
At 40 weeks, your baby is about the size of a watermelon (tarbooz), around 51.2 cm from head to heel (NHS), with a WHO median estimated weight of about 3,617 g. Every part of your baby is now well developed, though the skull bones stay a little soft so they can pass through the birth canal. Only a small number of babies arrive on their due date, and most women experience early signs of labour between 37 and 42 weeks.
Your Baby at 40 Weeks
Every part of your baby is well developed, including the bones, although the bones of the head stay a bit soft and flexible so they can fit through the narrow birth canal, which is why a newborn's skull can look slightly pointed. A well-grown baby at term can weigh anywhere from 2.9 kg to 4.2 kg, as babies come in all shapes and sizes (Pregnancy, Birth and Baby).
Your baby is rather squashed up now but should still be moving in their usual pattern. Movements should not slow down or stop; if you notice any change, contact your midwife or maternity unit straight away, as someone will answer calls 24 hours a day (NHS).
Your Body This Week
Practice contractions are likely now and should not be painful, whereas real contractions hurt as your bump tightens and ease as the muscles relax. Labour has three stages: contractions open your cervix to 10 cm (6 to 12 hours, or less if you have had children before), then your baby is born, and finally the placenta comes out (NHS).
It can feel as though you have been pregnant for ever, and being overdue is uncomfortable, but there is usually no need to worry. If you go more than 10 to 12 days past your due date, or there is a risk to you or your baby, your doctor or midwife may recommend inducing labour, and any decision should be made in consultation with you (Pregnancy, Birth and Baby).
When to call your midwife or doctor: Call your hospital or midwife when contractions last at least 60 seconds and come every 5 minutes, and call your midwife or doctor for advice if you think your waters have broken, even if it is only a trickle. Contact your midwife or maternity unit straight away about any change in your baby's movements.
Garbh Sanskar This Week
A small daily practice for this stage, from Mamta’s 1:1 sessions. It is tradition and gentle self-care, not medical advice, so keep every check-up and follow your doctor or midwife first.
- Mantra: The Purnamadah invocation from the Isha Upanishad says that from the whole, the whole arises, and the whole remains: a gentle thought as you wait to meet your baby. Say it slowly and softly for a few minutes; the Garbh Sanskar mantras guide gives the full verse.
- Music: If music is part of your birth preferences, keep your calm playlist charged and ready in your bag. The NHS labour tips include doing something that helps you relax, because feeling calm helps you manage labour better than feeling stressed.
- Gentle movement: For daytime early labour, the NHS suggests staying upright and active, trying different positions such as rocking on a birth ball, and breathing in through your nose and out through your mouth with a relaxed jaw. Mamta teaches this same slow breathing as a short daily practice now, only with your doctor's or midwife's clearance, never holding the breath.
- Food: Traditionally, Charaka's ninth month offers therapies for a qualified practitioner rather than a home food, so keep meals simple. For labour, the NHS suggests something healthy for energy, such as a banana or low-fat yoghurt, and avoiding fatty or sugary foods, alongside the iron, calcium and folic acid your doctor recommends.
- Garbh samvad (a line to say to your baby): We have waited so long to meet you. Welcome, whenever you choose to come.
Questions About Week 40
What happens if I go past my due date?
Only a small number of babies are born on their due date, and your doctor or midwife will monitor you and your baby carefully. If you go more than 10 to 12 days over, or there is a risk to either of you, they may recommend inducing labour, a decision made in consultation with you.
Are there safe ways to bring on labour at home?
The NHS says there are no proven ways to safely bring on labour at home. Get advice from your doctor or midwife before trying anything other than watching and waiting.
How big is a baby at 40 weeks?
The NHS gives a length of around 51.2 cm from head to heel, and the WHO Fetal Growth Charts put the median estimated weight at about 3,617 g. Pregnancy, Birth and Baby notes that a well-grown term baby can weigh anything from 2.9 kg to 4.2 kg, so your own baby's size may differ.
Practise With Mamta, Wherever You Are
Mamta guides expecting mothers through private 1:1 Garbh Sanskar sessions online, scheduled in your own time zone, from the first trimester to the last week. Start with a free conversation on WhatsApp or read how sessions work.
Sources
Mamta is not a doctor. Medical points on this page come from the sources below, checked in October 2026. Sizes are approximate and babies vary; your scan report is what matters.