Quick answer: Week 27 begins the third trimester. Your baby measures about 36.6cm from crown to heel and weighs around 875 grams, with the brain forming its folds and grooves and hearing well developed. From 28 weeks antenatal appointments become more frequent, and anti-D is offered if you are rhesus negative. If movements reduce or feel different, contact your midwife or maternity unit immediately.
What parents need to know
Congratulations — you've reached the third trimester! Week 27 marks the beginning of the final stretch of pregnancy, and your baby is growing and developing remarkably quickly. The third trimester brings new considerations, and your antenatal appointments will become more frequent from here on.
| Length | About 36.6cm crown to heel |
|---|---|
| Weight | Around 875 grams |
| Trimester | Third trimester begins |
| Appointments (first baby) | 28, 31, 34, 36, 38, 40 and 41 weeks |
| At 28 weeks | Anti-D if rhesus negative, plus anaemia blood test |
How big is your baby at 27 weeks?
Your baby now measures approximately 36.6cm from crown to heel and weighs around 875 grams — roughly the weight of a head of cauliflower. They're beginning to look more like a newborn, though they are still quite slim and will triple in weight before birth.
What's happening with your baby?
Your baby's brain continues to develop at a remarkable rate this week, and the surface of the brain — which was smooth earlier in pregnancy — is now forming its characteristic folds and grooves (gyri and sulci). These folds dramatically increase the surface area of the brain, allowing for the complex neural connections that support thought, memory, movement, and sensation. Your baby's eyelashes are now growing, and they can blink their eyes open and shut. Their hearing is well developed and they can recognise the sound of your voice, your heartbeat, and other familiar sounds from the outside world.
What's happening in your body?
The third trimester brings new challenges as your growing bump puts increasing pressure on your body. Heartburn and indigestion are common as the growing uterus pushes against the stomach. Eating smaller, more frequent meals and avoiding lying down immediately after eating can help. Sleeping may become more difficult, and many women find a pregnancy pillow helpful for supporting the bump and reducing pressure on the hips and back.
Shortness of breath can occur as the uterus rises in the abdomen and puts pressure on the diaphragm. This typically improves somewhat as your baby 'drops' lower into your pelvis in the final weeks. Mention any significant breathlessness to your midwife.
Your antenatal care in the third trimester
From week 28, your antenatal appointments will become more frequent. NHS guidelines recommend appointments at 28, 31, 34, 36, 38, 40, and 41 weeks (if you haven't delivered by then) for first-time mothers, and at 28, 34, 36, 38, and 40 weeks for women who have previously given birth. At these appointments, your midwife will check your blood pressure, test your urine, measure your fundal height, check your baby's position and heartbeat, and discuss any concerns.
At 28 weeks, you'll be offered anti-D injections if you are rhesus negative. This is important to protect any future pregnancies. You'll also be offered a blood test to check for anaemia.
Fetal movements in the third trimester
As you enter the third trimester, it's more important than ever to be aware of your baby's movements. By now, you should have a good sense of your baby's usual pattern of activity. According to Tommy's and NHS guidance, there is no specific number of movements you should be feeling each day — what matters is that you are familiar with what is normal for your baby and notice any change. If your baby's movements reduce or feel different, contact your midwife or maternity unit immediately — do not wait until the next day. Never use a home Doppler to check your baby's heartbeat as a substitute for seeking medical advice.
Your week 27 checklist
This week:
- Celebrate reaching the third trimester.
- Familiarise yourself with your baby's movement pattern.
- Ensure you know how to contact your maternity unit if you are concerned about movements.
- Make note of your upcoming antenatal appointments.
- Start thinking about your hospital bag.
Sources & further reading
- NHS — You and Your Baby at 27 Weeks Pregnant
- Tommy's — Week 27 of Pregnancy
- NCT — Week 27 of Pregnancy
General information, not individual medical advice. Speak to your GP, midwife or health visitor about your baby’s needs.
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