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Third Trimester

Three women with partners, antenatal class

The third trimester starts in week 27 and usually ends at week 40. The baby becomes increasingly prepared for birth as it grows throughout the trimester, and delicate organs like the lungs mature and become more functional. Most babies start to turn head-down from about the 28th week in preparation for their birth.

  • Babies can put on up to ½lb (225g) a week
  • Fat makes up most of this weight, as keeping warm is essential for babies after birth
  • The baby’s eyes, ears and lungs become mature and fully-functional
  • At birth, babies are usually about 18 to 22 inches long (46-55cm) and weigh 6 to 10 lbs (3-4 kg)

i 21-week old fetus



  • The baby’s eyelashes grow; it opens and closes its eyes and can notice changes in light
  • The baby can hear the outside world clearly over its mother’s heartbeat
  • The baby exercises by kicking and stretching
  • At 28 weeks, most babies begin to turn head-down
  • The testes of baby boys start to descend
  • By the end of the month, babies are about 40 cm (17 inches) long and weigh about 1 kg (2.2 lbs)
  • Most babies born at the end of the sixth month survive with the help of specialist assistance


  • She’s still likely to have constipation, heartburn, indigestion, flatulence and bloating
  • She may have aching in her lower abdomen
  • If she has a whitish vaginal discharge, it’s probably getting heavier
  • Other symptoms may include leg cramps, backaches, varicose veins, mild swelling, shortness of breath, difficulty sleeping and clumsiness
  • She may feel “Braxton Hicks” contractions that are usually painless and involve the uterus hardening for a minute and then returning to normal
  • Feeling bored and a bit tired about their pregnancy is quite normal at this point!


  • Keep exercising regularly. Special yoga classes or swimming are good for keeping fit and supple, and many mothers find these useful
  • Keep the father involved and informed of what’s going on, as it’s difficult for most men to really “engage” until the baby has arrived



  • The baby continues to grow and get ready to be born. The saying is that from now, “every day spent in the womb is two days less your baby would spend in hospital”
  • The baby can hiccup and cry and responds to pain, light and sound
  • The baby’s taste buds are developing
  • The baby is making red blood cells entirely from their bone marrow
  • The fingernails have reached the end of the fingers
  • If the baby is a boy, his testes have descended into his scrotum
  • This month, babies grow a lot and will be about 40 to 45 cm (16 – 18 inches) long and weigh about 1.8 kg (4 lbs)


  • The baby’s presentation is usually found now with an ultrasound. If the baby’s breech or transverse, then moxa and acupuncture can gently ‘turn the baby’. An ultrasound is recommended before these treatments to rule out any potential risks
  • Now’s the time to discuss birth plans with your midwife and partner
  • She’ll feel regular, strong activity from the baby
  • Discomforts such as constipation and shortness of breath tend to be more frequent, and Braxton Hicks contractions increase; these soften the cervix and prepare it for delivery
  • Mixed emotions for a wish to have the pregnancy over, and concerns over the labour, delivery and the baby’s health are normal right now


  • Now’s a time to take stock and prepare for the next two months or so. Make plans, prepare bags and talk to the people who need to know things
  • Take exercise and spend time resting or with friends if possible; try your best to support your support group at this time



  • The baby is still putting on about 225g (½ lb) a week until the 37th week when it slows down slightly
  • The baby is getting ready for birth, with its head against the birth canal. The baby is in the fetal position with its legs tucked to its chest
  • The umbilical cord is taut, which prevents it from tangling
  • The baby’s sleep patterns are settling
  • The baby’s head is soft and flexible, which eases its delivery through the birth canal; the bones will spring back into shape after the journey
  • The baby’s lungs are mature, and the baby will be fine if born a little early


  • In addition to the familiar discomforts, aching in her buttocks and pelvic area with some backache and heaviness may be an issue
  • Sleeping is usually difficult now
  • Braxton Hicks contractions will be more frequent and intense as the cervix prepares for delivery; it gets shorter, thinner and more open in a process called ‘effacement’
  • As the baby’s lower down, it will be easier to breathe, but there will be more visits to the bathroom as the pressure’s now on the bladder!
  • She’ll probably be feeling excited, anxious, apprehensive and relieved that it’s almost over


  • If the Braxton Hicks are a problem, there are things you can do that may help:
    1. Drink more water; this can lessen them as dehydration causes muscles to spasm
    2. Breathing exercises also help to stop them and reduce the pain
    3. Lying on your left side eases the pain of contractions
    4. Visiting the bathroom as a full bladder can start them off
  • The due date is a rough guide; most births are two weeks before and after this time
  • If you don’t go into labour spontaneously, you’ll probably be offered a medical induction, usually with a drug called “oxytocin”
  • Acupuncture is an alternative to induce labour before you agree to the drug induction
  • Remember to pack your bag(s) so that you’ll be ready to get out the door when the time comes!
  • Have a baby seat for the car as most hospitals won’t allow you to take the baby in a car without one

Good luck!!

For scientific literature and fully referenced information on drugs and other chemicals known to affect breastfeeding mothers and their babies (including suggestions for therapeutic alternatives), there’s the LactMed® database.

i CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=3537764