Trimesters 1, 2 & 3
TRIMESTER 1 (1 - 12 weeks):
- By the sixth week of pregnancy the embryo is already encased in an amniotic sac of fluid. It's grey in colour and jelly-like, but already has a heart the size of a poppy seed which is beating on its own.
- By 9 weeks your baby measures around 3cm (1in) and is starting to look like a real baby. Limbs are developing and fingers and toes are nearly complete.
- A 12-week embryo measures around 8cm (3in), all major body organs have formed and he or she's already making jaw movements, sucking and swallowing.
TRIMESTER 2 (13 - 26 weeks):
- The second trimester is when your baby becomes more recognisably human - the neck uncurls, eyes are closer together and arms and legs, fingernails and toenails are well developed.
- Between 17 and 20 weeks you may actually start to feel the baby move - more a fluttery sensation than an actual kick at first. His or her growth will also accelerate. Baby can suck his or her thumb, hiccup and hear your voice.
- By the end of the second trimester at 24 weeks it would be possible now for your baby to survive if he or she arrives prematurely. He or she would need intensive care, but increasing numbers of babies are surviving at this age.
- Your baby weighs about 550g (just over 1lb) and measures about 20.5cm (8in) from crown to rump. Fat stores are beginning to be laid down and he or she can now wiggle their toes and grip with their hands.
TRIMESTER 3 (27 - 40 weeks):
- By the start of the third trimester your baby is already laying down fat stores and the lungs are strengthening in preparation for birth. He or she measures 24.5cm (9 1/2 in) and weighs 1.1kg (about 2 1/2 lb). Baby is now able to tell the difference between night and day and is starting to recognise your voice. The skin is covered with vernix, a thick white grease, which protects against absorbing too much amniotic fluid - this will usually have disappeared by the time he or she is born.
- By 36 weeks your baby is close to its full term length of around 46cm (18in) and weighs about 2.75kg (6lb). Growth won't be as rapid now, but weight gain should continue at about 250g (9oz) a week. The vernix and lanugo - fine body hair - should be disappearing now.
- By the time you reach the 38th week of pregnancy your baby will be ready to be born at any time during the next four weeks. He or she measures about 48cm (14 in) from crown to rump and weighs an average of 3.15kg (6lb 13oz). There's not much room left inside now so movements won't be so vigorous.
