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Third trimester of pregnancy

The third trimester of pregnancy – what to expect

The third trimester of pregnancy is the last 3 months of pregnancy, from week 29 to 40. Babies born between weeks 37 and 42 are considered full-term, and any births before 37 weeks are premature. The end is near and it won’t be long until you have your baby in your arms. You may be feeling excited, but feeling apprehensive or anxious about the new arrival is also very common. 

In the third trimester, your baby will continue to grow and develop and gain weight each week and has a better chance if born early. Your antenatal appointments will increase in their frequency in the third trimester so your midwife can more closely monitor the health of you and your baby. 

Changes to your body

  • Your uterus will continue to grow to accommodate your growing baby. This will lead to a bigger bump, and overall less space in your abdomen. You may be more uncomfortable, and find it difficult to find a good sleeping position. 
  • You might find it difficult to take deep breaths as the growing uterus pushes on your diaphragm. Any new breathlessness or pain with breathing should be discussed with your healthcare provider. 
  • You may need to pass urine more frequently. Pressure on your bladder can lead to more frequent trips to the loo.
  • Blood pressure may decrease as the baby puts pressure on a large vein in the abdomen. 
  • You may have swollen ankles. Pregnancy can lead to fluid retention. Try putting your feet up and avoid standing for long periods of time. Ankle swelling can also be a sign of pre-eclampsia (insert hyperlink), along with other symptoms such as headaches, vomiting and visual disturbances. If you are concerned about any symptoms, please speak to your GP or midwife urgently.
  • Braxton-Hicks contractions may start to happen, which are irregular, infrequent contractions or uterus tightenings that happen in preparation for labour. 
  • Leg cramps may become more common. 
  • Stretch marks may appear on the abdomen or breasts.
  • Constipation – high levels of progesterone can lead to constipation and bloating. Make sure you are drinking plenty of water and eating a fibre-rich diet. Being physically active will also help. 
  • Heartburn – this can begin from the first trimester and may continue into the third.  Pregnancy hormones relax the valve between your stomach and your oesophagus allowing acid to reflux up the oesophagus. Your growing baby will also put pressure on your stomach. Avoiding heavy meals and food triggers such as spicy foods can help. Gaviscon can help to ease symptoms and if severe, a medication called Omeprazole may be prescribed. 
  • A white-coloured vaginal discharge – this is a normal response to hormonal changes. However, if you are concerned that your discharge is abnormal, has an odour, or is associated with symptoms such as vaginal/vulval itch or soreness then it could be a sign of an infection and you should speak to your midwife or GP. 
  • Colostrum (a fluid in the breasts that nourishes the baby in the first few days before milk comes in) may begin to leak from your nipples. 
  • Back pain – carrying the extra weight can sometimes lead to musculoskeletal pain. Speak to your GP or midwife and ask for a physiotherapy referral if this is becoming problematic. 
  • Skin pigmentation or Melasma – this can occur due to hormonal changes but should reduce after pregnancy.
  • Varicose veins – the pregnancy can lead to increased pressure in the venous system and you may get varicose veins on the legs and sometimes on the vulva. 
  • Haemorrhoids – swollen veins in the anus and rectum are a common feature in pregnancy and can lead to anal pain and bleeding. Avoid straining by keeping stools soft through drinking plenty of water and a high-fibre diet. Ice packs and pads may also relieve symptoms. 

Do’s and don’ts in the Third Trimester

  • Smoking and alcohol consumption are not advised in pregnancy and caffeine should be limited to 200mg a day. 
  • You can exercise as normal, but avoid contact sports or activities that could easily result in injury such as horse riding. In the third trimester, you may feel more tired and want to slow down a bit, but it is important to keep active if you can. During the second and third trimesters, it is also advised to avoid exercise and activities where you are lying on your back for prolonged periods of time. 
  • Make sure you are sleeping on your left side at night. Lying on your back can put pressure on important blood vessels in the abdomen that supply the uterus. There is an increased risk of complications such as stillbirth.
  • Aim to eat a well-balanced diet, rich in fibre and fruits and vegetables. There are some foods you need to stay clear of pregnancy – see our blog here (insert hyperlink). You do not need to eat for two! 
  • It is advised to continue taking Vitamin D in the third trimester but Folic acid can be stopped by week 12. 
  • To help keep your gums healthy, make sure your brush and floss regularly and book in with a dentist for a review. 
  • It is safe to continue to be sexually active, sexual intercourse does not harm the baby unless you have specific circumstances whereby you midwife or GP has advised caution. 
  • Saunas, hot tubs and long hot baths or showers should be avoided as pregnant women are more prone to overheating and fainting.  
  • Consider booking into antenatal classes or breastfeeding classes to get as prepared as possible for the new arrival and hopefully make some new friends who are in a similar situation. Peer-to-peer support is hugely valuable as a new mum!
  • Create a birth plan with your midwife or partner to ensure your wishes are clear.
  • Pack your hospital bag. It’s normally recommended to do this from 37 weeks so you are prepared for any early arrivals!
  • Start getting some baby stuff for your little one and set up your nursery with essentials.
  • Prepare to breast feed if you plan to. It’s a good idea to schedule a breast-feeding class so you can learn about it before the baby arrives. Most antenatal units should have these on offer. 
  • If available to you, consider a tour of the labour ward or birth centre. This can help you feel prepared for the big day and reduce anxiety.
  • Stock your fridge! Whilst you have the time, do some batch cooking of easy meals that you can bung in the freezer. You will be thankful for this when your newborn is here and time to cook is limited!
  • Consider colostrum harvesting.
  • Avoid travelling too far from home in the later stages of the third trimester. Some modes of transportation, such as air travel, are restricted from 36 weeks. 


Whooping cough

Expectant mothers can protect their babies from birth by having the whooping cough vaccination whilst pregnant. The best time to get vaccinated is between weeks 16 and 32 of your pregnancy.



Pregnant women are at higher risk of developing complications from the flu virus, and it is therefore advised that they have the seasonal flu vaccine.


COVID-19 vaccine

It is strongly recommended to get vaccinated against COVID-19 if you are pregnant. Vaccination creates antibodies against the virus that can also help protect your unborn child. You can be vaccinated at any stage of your pregnancy. Pregnant women are more at risk of getting serious complications from COVID-19. There is no evidence that the vaccine is unsafe for the pregnancy.

Your baby

During the third trimester, your baby will continue to grown and develop. Their organ systems will continue maturing and they will gain weight. The lungs continue to develop and are fully mature by about 38 weeks. Normally the fetus will start to position themselves head down, and begin to engage in the pelvis towards the end of the third trimester in preparation for birth. Your midwife will be checking the position of your baby throughout the third trimester. If the baby is head up, called Breech position, it could affect the way you are advised to deliver (e.g. Elective C-section) or you may be offered a repositioning procedure called External Cephalic Version.


In the final weeks of pregnancy, meconium – the baby’s first poo- begins to accumulate in the digestive system. Babies will normally pass this in the first 24 hours of birth. Your baby is developing all of its senses. They can hear your voice and may perceive light and dark. The layer of downy hair, called lanugo, that has covered your baby will start to fall off. The baby is covered in Vernix, which is a creamy soft layer that protects the baby’s skin. 


It’s possible that as your baby grows, there is less space for them to move and your foetal movements may change. It’s still important to monitor movements and report any reduced movements to your midwife team urgently.

Your care



You will not normally be offered any scans in the third trimester unless your team need to monitor the development or growth of your baby.




Appointments normally increase in frequency in the 3rd trimester and you will be seen every few weeks as they monitor you and your baby more closely. At each appointment, your GP or midwife will check you feel well, check your blood pressure and urine for protein and measure and listen into baby.


31 weeks

If this is your first baby, you will be offered an appointment at 31 weeks. Your midwife will review and discuss any results, measure and listen into baby and check your blood pressure and urine for protein. 


34 weeks

In addition to the normal checks, your doctor or midwife should also give you information on preparing for labour and birth and support you in making a birth plan. You will be offered your second anti-D treatment if you are rhesus negative. 


36 weeks 

In addition to the normal checks for you and your baby, your midwife or doctor should also give you information about breastfeeding and caring for your baby. They will also talk through vitamin K injection that is offered to the baby and screening tests for your newborn. If your baby is breech, you will be talked through possible options, including a delivery by Caesarean section or trying to reposition your baby through a procedure called External Cephalic Version. This normally takes place at 36 weeks. 


38 weeks and 40 weeks 

In addition to the normal checks for your baby, your midwife or doctor will discuss options and choices available to you if your pregnancy lasts longer than 41 weeks. This might include induction of labour. 


41 weeks 

In addition to the normal checks for you and your baby, you may be offered a membrane sweep to try and get labour started but there is no guarantee that it will work.  A membrane sweep is an internal examination. Your midwife will put a gloved finger into the vagina and make circular movements. The aim is to try and separate the membranes of the amniotic sac surrounding your baby from the cervix. This can release a hormone called prostaglandins which can induce labour. At this appointment, your midwife will also discuss induction of labour.


42 weeks 

If you have not had your baby by 42 weeks and have chosen not to have an induction, you will be offered more appointments and increased monitoring of the baby.


Dr Anna Cantlay

Dr Anna Cantlay - GP and Chief Medical Officer at For The Creators

Dr Anna Cantlay is an experienced NHS and private GP based in London.

Anna’s priority and passion is making healthcare convenient, accessible and personalised to you and your family. Anna is passionate about Womens Healthcare and is a Menopause specialist.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. For The Creators has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions.