40 weeks pregnant
At 40 weeks you are in the third trimester, and your baby measures about 51 cm from head to heel and weighs about 3.5 kg, roughly the length of a ukulele. The due date is this week, a membrane sweep may be offered at the 40-week visit, and only about one in twenty babies arrive on the date itself.
Weighs about 3.5 kg, like an average house cat. Averages from standard growth tables; your scan gives your baby's own numbers.
Your baby at 40 weeks
Due date. The average birth weight in Australia is about 3.3–3.4 kg. Most babies have turned head-down by now and have little room left to move.
How you might feel
Waiting is the hardest part; strong Braxton Hicks, a show and back pain are common, and keep monitoring the baby's movements.
A membrane sweep may be offered. Keep monitoring movements.
Call the maternity unit today for any change in your baby's movements, bleeding, fluid loss, a severe headache or vision changes. 13 HEALTH (13 43 25 84) in Queensland; 000 in an emergency.
What's due this week in Australia
Lodge the Parental Leave Pay and Family Tax Benefit claims
You can lodge up to 3 months before the due date through myGov → Centrelink.
40-week antenatal visit (first pregnancy)
A membrane sweep is usually offered from 40 weeks, and a plan is made for monitoring past the due date.
41-week visit and post-dates plan
A membrane sweep is offered and the baby’s wellbeing is checked (CTG and a fluid scan).
Coming up: Induction of labour window
If labour has not started, induction is offered between 41 and 42 weeks.
Checklist for the week
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Questions about 40 weeks
How many months is 40 weeks pregnant?
Nine months, the due date.
What trimester is 40 weeks?
Week 40 is in the third trimester. In the Australian guidelines Hello Bub follows, the first trimester runs to 13 weeks, the second from 14 to 27 and the third from 28 weeks.
What is a membrane sweep?
A midwife or doctor sweeps a finger around the cervix during a vaginal examination to separate the membranes, which can trigger labour within a few days. It is offered from 40 weeks to reduce the chance of needing an induction.
Written by the Hello Bub team; medical schedule follows the Australian Pregnancy Care Guidelines; last reviewed 3 November 2026.