31 weeks pregnant: baby is the size of a coconut

Your baby this week

Your baby's five senses are working. Your baby can hear, see light and dark, taste, smell and feel touch. The pupils change size in response to light, and your baby can turn the head from side to side. The lungs keep practising with breathing movements.

Your baby is gaining about 0.2 kg (half a pound) a week, mostly as fat, and it is filling out. The skin is becoming smoother. There is less room to move, so the movements you feel may change from big rolls to pokes, jabs and stretches.

How it happens. Your baby's brain now has billions of connections, and they form fastest in these last weeks. Your baby is practising for life outside by breathing, sucking and swallowing.

Your body this week

Your uterus reaches up to about 31 cm above the pubic bone, and it is squeezing your other organs. You may feel out of breath, need to pass urine often and have heartburn. Your body is also beginning to prepare for labour, and the uterus muscle practises tightening.

This practice is what you feel as Braxton Hicks contractions, named after the doctor who described them. They can start as early as the second trimester, but most people notice them in the third.

What Braxton Hicks feel like

Braxton Hicks are tightenings of the uterus. Your belly feels hard and firm to the touch, and you may see the shape change. They can be uncomfortable but are not usually painful. They tend to be:

• Irregular. They come at random times, with no pattern.
• Short. They last from about 30 seconds to a couple of minutes.
• Felt mostly at the front. Most people notice them in the belly or groin, rather than the back.
• Eased by rest. They often settle with a change of position, a walk, a rest or a glass of water.
• Not getting stronger. They do not build in frequency or intensity.

Common triggers include dehydration, a full bladder, being active, being touched, sex and your baby's own movement.

How to tell them from real contractions

The difference is usually pattern and progression. Real contractions, in labour, are:

• Regular. They come at set intervals, and the gaps get shorter.
• Longer and stronger over time. They build up.
• Not eased by rest. Changing position or drinking water does not stop them.
• Often felt in the back and wrapping to the front. Many people feel them as a period-like ache or pressure.
• Sometimes joined by other signs, such as a bloody show, watery fluid or a change in discharge.

If you are unsure, try this: drink a large glass of water, empty your bladder, lie on your side and rest for an hour. If the tightenings stop, they were probably Braxton Hicks. If they continue, get stronger or come closer together, call.

What to do before 37 weeks

Because you are not yet at term, be cautious. Call your maternity unit or provider promptly if you have:

• Regular tightenings, or ones that are painful or getting stronger
• Period-like cramps, a new dull backache or pelvic pressure
• A change in vaginal discharge, or any bleeding
• Fluid leaking from the vagina
• Reduced movement from your baby

Note the time of each tightening and how long it lasts. If it turns out to be nothing, that is good news, and providers would rather check than have you wait. For more on preterm labour, see week 24. Signs of labour at term are covered in week 37.

Leaking urine

Leaking a little urine when you cough, sneeze or laugh is called stress incontinence, and it is common in late pregnancy because your baby presses on the bladder and your pelvic floor is under strain. It is not a sign of anything serious. Pelvic floor exercises (see week 13) help, and wearing a pad can make you more comfortable.

Fluid leaking that is constant, or a gush, may be amniotic fluid rather than urine. If you are not sure, wear a pad, note the colour and smell, and call your provider.