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Pregnancy health centre

39 weeks pregnant

WebMD Medical Reference
Medically Reviewed by Dr Rob Hicks


How is your baby growing at 39 weeks?

The average size of a baby in week 39 is 51cm and 3.4kg (7.5lb), but remember babies vary in size and yours might be lighter or heavier. Your baby's head will be about 10cm in diameter. While your baby is waiting for childbirth, he or she will continue to put on some weight. Your baby's skin will be paler and thicker.

There won't be much room for your baby to move, but you should still feel some movements. Movements may feel more like squirming than kicking.
At the same time your baby has been swallowing amniotic fluid for the past several weeks, he or she will also have been taking in waste material from dead skin and blood cells, the fine lanugo hair that has been shedding and other waste products. These will form in the intestines into the greenish-black meconium – your baby's first poo. The meconium can be present in your waters when they break or appear after birth.

The placenta will continue to supply nutrients and oxygen to your baby, who may sleep through part of the first stage of labour – which may be about to start any day or not for another couple of weeks. Once your baby is born and takes the first few breaths of fresh air, the umbilical cord will no longer function and changes within your baby's heart will pump blood to the lungs.

How are you changing in week 39?

You are most likely a bit anxious, waiting to go into labour. Your breasts may be leaking colostrum, the baby's first milk that will be rich in antibodies to protect him or her. At any stage you may have signs indicating you are in the first stage of labour: you may have a sudden surge of energy (the "nesting" urge) – or you may feel fatigued – you may have a show, your waters may break or you may start feeling your first labour pains.

Braxton-Hicks contractions may be getting strong enough that you might wonder if they are real contractions. However, a change in contractions may be a sign that they are the real thing. Labour contractions differ from Braxton-Hicks contractions, which are uncomfortable not painful, and don’t build-up. In labour, contractions are felt as a tightening sensation across your abdomen and into your back, caused when the muscles in the womb shorten, pulling up on the cervix and down at the top of the womb. The contractions begin gently, peak and then fade away. If you put your hand on your bump during a contraction, you will feel it becoming harder. As a contraction fades, the muscles lengthen again, but in the next contraction they may shorten a bit more than the previous one, pushing the baby a little further down towards the cervix. In a first pregnancy you may have gentle contractions for 6–10 hours. However, every pregnancy is different, so this first stage of labour can be shorter or longer – in women who have had babies previously, it is often shorter.

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