Your pregnancy: weeks 13, 14, 15, 16

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This guide to your pregnancy tells you how your baby is developing week by week. It also tells you a bit about how your body may be changing and how you might be feeling. Remember, not all babies develop exactly like each other so this can only be a general guide: you should ask your doctor or midwife for any specific information about your pregnancy. We all know babies come in two flavours, but - as most of you won't know what flavour you're getting - for clarity we'll refer to your baby as 'she'.

How your baby is growing | How your body is changing

Your baby will be looking more like a little human by the end of this period. This is because her face is sorting itself out and the rate her body is growing has speeded up to catch up with her head. By now, she will be around 14cm long and weigh around 200g.

How your baby is growing

Your baby's eyes, which have been a bit to the side, now take up their rightful place looking straight ahead. Although closed, they'll be moving slowly under her eyelids. Meanwhile, her ears, which started as little buds, move to the side of the head - where they belong - and stand out a little. Your baby also looks more human because she has grown a proper neck, which means her chin is no longer touching her chest.

It seems rather early but your baby's hair pattern is sorted out at this time. A baby's body and head are covered from now until birth with a fine, wispy layer of hair called lanugo, from a Latin word meaning down. Lanugo is thought to help insulate babies and keep them warm.

By 16 weeks your baby's head is much smaller compared to her body than it was at 12 weeks. Her legs have got longer too and are developing well. They are about one third of the length of her body and are now longer than her arms. She's also starting to grow nails on her fingers and toes.

All the time your baby's arms and legs are developing proper hard bones: the first bone that is formed is actually the clavicle, we have two - one each side at the base of our neck. The second is the thigh bone (the femur). If you have an ultrasound around this time you can see your baby is growing itself a skeleton.

You may also be able to get an experienced ultrasound operator to tell you the sex of your baby, as the genitalia is well formed at this time. If you have a girl baby her ovaries will be developing and moving to their proper place in her pelvis. In boys, the prostate gland develops around this time.

Babies are notorious for refusing to cooperate when having an ultrasound and unless your ultrasound operator can get a clear view they're unlikely to commit themselves.

Your baby's moving around quite a bit, kicking, flailing her arms and grasping with her hands. She has bursts of activity, stretching her legs and arms. Her muscles are developing, as are the nerves that make them work, and it's thought this activity is practice for the outside world so that each group of baby muscles knows what it's meant to do when it grows up.

Sometimes you can feel your baby practising. This is called 'quickening' and is much less obvious than feeling proper movements. You're more likely to feel them if you've had a baby before as you'll know what it feels like.

Your baby's skin doesn't look much like it will do at birth. It is thin and transparent enough to be able to see blood vessels in places. Your baby doesn't have any fat yet, so she looks vaguely pink and skinny.

All the organs in your baby's body are continuing to grow. Her pancreas will be producing insulin, which is needed to control levels of sugar in the blood, and her liver is making bile. Your baby's stomach and bowels are all growing bigger and, on the inside, the bowel is developing little finger-like projections called villi, which absorb important nutrients from the food we eat into the blood stream.

Your baby's lungs are also growing and your baby will be practising how to breathe. She doesn't need to breathe 'properly' in your womb because her blood largely bypasses the lungs and gets the oxygen it needs through the umbilical cord. But as soon as she's born she'll need to breathe because she'll need oxygen from the air around her - the umbilical cord and the placenta are history - so wisely, she has a gentle try-out before birth. Because she's surrounded by amniotic fluid, this means she's effectively breathing underwater.

Meanwhile, your baby's heart has already stormed ahead in development, folding itself from a hollow muscular tube into a small fist-like muscle with four chambers. It pumps around six gallons of blood a day. If you hear its heart beat (through a Doppler machine that your midwife or doctor uses) it can sound alarmingly fast - like a mad galloping pony. This is normal. Your baby's heartbeat is around twice as fast as your's.

How your body is changing

• Sickness

Some women feel sick (and are sick) from the moment they conceive to the moment the baby comes out. This isn't uncommon but many women are lucky enough to stop feeling sick around this time. This usually extends to being able to tolerate smells that, while you felt sick, were stomach turning.

• Body shape

You may enjoy eating more and, even if you don't, you are likely to develop a bulge that means goodbye to tight jeans. The bulge is actually your womb rising out of the pelvis to occupy part of your lower abdomen. You can just about feel it and it may make sleeping on your tummy uncomfortable.
More about your body during pregnancy

• More energy

Usually you should feel less exhausted around this time. Unfortunately, this is a temporary state and you will feel even more tired later on (and even more tired after the baby is born). It's helpful to start taking some exercise - I promise. Being fit for having a baby stands you in good stead for recovering from labour and is good for your baby. By being fit, I mean taking regular walks or going swimming, not doing an hour's intensive aerobic exercise at the gym.

• Constipation

This problem will feature from now until you give birth. It's caused by the higher level of hormones in pregnancies that have the side effect of making your bowel move slower than usual. You will find what works for you, but fruit and vegetables help.

More about your body during pregnancy 

Remember, you can chat to other mums about all the 'joys' of pregnancy on our Pregnancy Talk boards.

Weeks 6-8 | Weeks 9-12 | Weeks 13-16 | Weeks 17-20 | Weeks 21-24 | Weeks 25-28 | Weeks 29-32 | Weeks 33-37 | Weeks 39-40