Your Baby's Development
Almost from the first moment you become pregnant, your baby develops inside you at an amazing rate. This can vary slightly between babies but these are the major milestones;
From the second your egg is fertilised, your baby’s genetic blue print is set – from his or her sex, eye and hair colour to his or her height. Your body has already started making amniotic fluid to cushion and protect your developing baby. By the end of the first month, the heartbeat can be detected on a scan and he or she is about the size of a grain of rice.
By now, your baby’s heart, lungs and kidneys are already in place and starting to develop. The facial features are starting to form and by week five, your baby measures around 7mm in length.
By now your unborn baby is the size of a small lime and its face is starting to develop some human features. The skin is transparent and the sex organs start to develop but at this stage it is still hard to tell whether your baby is a boy or girl. The end of this month also marks a major milestone since after the 12th week of pregnancy your baby is less susceptible to infections, and the risk of you suffering a miscarriage falls significantly. By week 12, your baby weighs around 14g (0.5oz) and is around 8cm (3in) long.
The placenta feeding your baby nutrients and oxygen is now fully formed. Although still tiny – about the size of an avocado – your baby can now suck its thumb and curl up their fingers and toes. Tiny finger and toenails start to appear, as well as hair, eyebrows and eyelashes. A very fine faint downy hair starts to grow all over baby’s body. This is called lanugo, which is thought to help keep the baby at the right temperature.
Although you are now half way through your pregnancy, your baby still has a huge amount of growing to do and is only a fraction of its eventual birth weight, typically weighing around 0.28kg (10oz) at this stage. However, growth starts to gradually speed up from this point as baby starts to put on around 56g (2oz) a week as muscle, ligament and fat all start to increase in quantity. By now, the skin is coated in a greasy white substance called vernix, which helps to protect the baby from the drying effects of the amniotic fluid in which it floats. All the senses – taste, smell, hearing, sight and touch – are well developed now and from 18 weeks, a loud noise can make your baby jump! By 20 weeks, a baby can get hiccups too as the lungs develop.
At this point, your baby is so well formed that it would stand a good chance of survival if born prematurely. The body has grown in proportion so the head now no longer looks too big and although the eyes are still closed your baby can sense both light and darkness. This is a time when movements are most active and most frequently felt because there is still a lot of room for your baby to move around. By week 26, your baby can recognise your voice too.
As you go into the final trimester of your pregnancy, your baby is putting on weight rapidly and laying down fat in order to be ready for life outside the womb. The lungs are now almost fully developed and should be producing a substance called surfactant, which helps them to mature and function normally after birth. Nerve cells are developing fast in the brain, helping regulate your baby’s body temperature.
Baby is now filling most of the space in your womb so you may feel fewer movements around this time. The lanugo hair and vernix covering the body both start to disappear and the intestine starts to fill with a green, tar-like substance called meconium. The internal organs are maturing fast, and your baby is now passing water in preparation for weeing after being born. The skin is now paler and less wrinkled than before.
Both you and your baby are now looking forward to seeing each other! At this stage there is little left to be done except gain weight and for the lungs to mature completely. Your baby’s body is likely to have settled in your womb upside down with the head engaged into your pelvis and is likely to arrive at any time – but less than 10% of babies appear on their due date! Most arrive afterwards, usually within two weeks.