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Trimester-by-trimester pregnancy guide
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Third trimester

At this time you might start to feel anxious about labour and wish you could have your baby now. Don't worry - this doesn't mean there's anything wrong. Your feelings of urgency are caused by metabolic changes in your brain. Subtle shifts happen in each trimester, bringing about the tiredness of the first, the elation and energy of the second, and now the anxiety of the third.

Physical changes

Third trimester
© DK

You're rapidly getting bigger now and you're bound to feel tired. You may not be sleeping as well as usual at night and you'll need to rest more and take naps during the day. As your ligaments stretch and give way, you might start to find walking around uncomfortable. Once your baby has settled into your pelvis, you'll find you won't feel so breathless because there's less pressure on your diaphragm.


Because your diaphragm can't move as much when your baby grows bigger, you breathe more deeply when you're pregnant. You take in more air with each breath, which allows for better mixing of gases and the more efficient consumption of oxygen. This lifts your ventilation rate from the normal 7 litres (12pt) of air per minute to 10 litres (17 ½ pt) per minute, an increase of more than 40 per cent. However, your oxygen requirements are only 20 per cent more. This leads to overbreathing, which means that you breathe out more carbon dioxide per breath than is normally the case. The low level of CO2 in the blood causes a shortness of breath, which you may find bothersome during this trimester. Relief from this should come when your baby engages in your pelvis and there's less pressure on your diaphragm.

Possible problems

Some women suffer from hypertension (high blood pressure) in later pregnancy. Major warning signs of this are swollen and puffy hands, wrists, ankles, feet, and face. Your doctor or midwife will check for these at your antenatal visits. Pre-eclampsia may interfere with the functioning of your placenta and prevent it carrying nutrients to your baby efficiently. If you do develop pre-eclampsia you may have to go into hospital.

Self-care in the third trimester

As the third trimester goes on, the extra weight you're carrying may cause more backache and make you feel tired all the time. You'll probably find it difficult to sleep in the last weeks, because it's hard to get comfortable in bed. Don't take sleeping pills - they'll make your baby sleepy too. Take your time with everything and make sure you get enough rest. Take catnaps during the day and be sure to give yourself some quiet times when you can relax. If you don't feel like making love or it's difficult because of your increasing size, you may find that massage helps you relax. Eat lots of fresh fruit and vegetables and drink at least eight glasses of fluid per day as you'll probably pass urine more often. You may be constipated at times.

Your antenatal care

You'll go for checkups more often during this trimester. Your doctors may suggest you have a number of different tests to assess your baby's health and wellbeing, such as ultrasound or fetal heart rate monitoring. At each stage you should be told what's being done and why. Unlike the special tests in the first and second trimester - chorionic villus sampling, amniocentesis, and cordocentesis (see Special Tests) - none of the tests at this time are invasive of your uterus. You'll have regular urine and blood pressure tests, and your feet and hands will be checked for possible swelling, although such swelling may be normal if there aren't any other symptoms. From your 36th week up to the start of labour, you'll go to the antenatal clinic more often than you did in the earlier months.

Preparing for your baby

By the time you're nearing the end of your third trimester, you'll need to have clothing and equipment ready. You never know - your baby might arrive early. You may find yourself thinking more and more about the labour and some women find that they worry obsessively. Try not to be too anxious. No one can predict what will happen during your labour, as every woman's experience is unique, but most births go without a hitch.

Third trimester weight gain

During the final months you'll probably put on about 5kg (10lb) in weight.

Of this, about 3-4kg (6-9lb) will be your baby. The rest is made up of your baby's support system (the placenta and amniotic fluid), your enlarged uterus and breasts, and the extra blood in your body. Your own fat stores will usually account for about the same weight gain as your baby.

Third trimester pregnancy

  • You'll probably get tired easily, although you may find it hard to rest.
  • You'll notice Braxton Hicks contractions more and more.
  • You'll have visited the hospital where you're going to give birth and met the staff. If you're planning a home birth you'll need to get everything ready.
  • You might worry about whether you can tell when you're in labour or not. Even for an experienced midwife or doctor, it can be difficult to know when labour has really started. Don't be afraid to ring your midwife or hospital delivery ward for advice if you're in any doubt.
  • If you often find yourself short of breath in the later stages of pregnancy, it'll help to sit in a semi-propped-up position whenever you can. Try not to overdo things.

Posted 30.06.2010


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