You've reached the four month mark and your baby is about 11cm long. Her legs are longer than her arms and she can wriggle and stretch.

Your body
You are showing more now and have a neat but obvious bump, which will be much more comfortable in stretchy or maternity clothes. By now, you've probably put on more than 2kg.

Making the first move
Most women first feel their baby move between 16 and 20 weeks of pregnancy (earlier in second or subsequent pregnancies) so don't worry if you haven't felt anything yet. Called 'quickening', these early movements feel like a fluttering butterfly, although at first you may dismiss it as wind!

Top tip
No action down below yet? Encourage your baby to shake a leg by lying down for a while (give your stomach a few prods if nothing happens).

Work it out
Although you may be tempted to become a couch potato for the next five months, you'll really feel the benefit if you take care of your body – and the bonus is that being fit-ish should help you cope during labour. Try some gentle stretches to improve your flexibility and relax you. Ideally, go to an antenatal exercise class – ask your midwife or GP to recommend one. Alternatively, invest in an antenatal exercise video so you can work out at home.

Your baby
Your baby is now 11.5cm crown to rump long. In the past two weeks, her weight has doubled to about 100g. This week, she begins to put on a little fat, which helps to keep her warm and maintain her metabolism. Her body now contains about 0.5g of fat and 89g of water.

What's happening now?
Although it will be quite some time before she'll be ready to join you for a workout, your baby's circulatory system is working. She gets oxygen from you and blood via the umbilical cord. This incredible lifeline grows to up to 50cm long and is about as thick as your index finger. Inside are two arteries (thick-walled tubes), which carry 'used' blood back to the placenta for recycling; and one vein that takes fresh, oxygenated blood back to your baby.

Have you felt your baby's first kick? These early movements feel like a fluttering butterfly.

The umbilical cord links your baby from her belly button to her life support system – the placenta.

Your baby has begun inhaling and exhaling amniotic fluid – this helps her lungs to grow and develop so they will be able to function properly when she takes her first breath of air.

Your baby's urinary tract is also working: her kidneys are excreting waste products as urine.

Did you know?
You and your baby's blood supplies never mix. The two supplies are separated by extremely thin walls, through which oxygen and nutrients pass from you to your baby. Her waste products pass back to the placenta.