Up to 40 weeks
Most women have their fertile time about 14 days after the first day of their menstrual period. Because of this doctors set an artificial, but convenient, timescale of 40 weeks, calculated from the date of your last menstrual period (see How the EDD chart works). A baby actually reaches “full term”, meaning he's fully developed, after about 38 weeks.
Your baby at 40 weeks of pregnancy
© DK
Your baby's progress
During this month your baby will usually shed most of the fine hair (lanugo) from his body. There may be some small patches left in odd places and perhaps some in his body creases.
His skin is smooth and soft, and there is still some vernix left on it (mostly on his back), which will help his passage down the birth canal. He'll be almost chubby before birth. His fingernails are long and may have scratched his face - they'll need trimming after birth. His eyes are blue, although they may change in the weeks after birth. When he's awake his eyes are open. In these last weeks, your baby produces increasing amounts of a hormone called cortisone from his adrenal glands. This helps his lungs to mature and prepare for his first breath.
Meconium
Your baby's intestine is filled with a dark green, almost black, substance called meconium. This is a mixture of the secretions from his alimentary glands together with the lanugo that's been shed from his body, pigment, and cells from the wall of his bowel. It'll be the first bowel motion he'll pass after birth, but he may pass it during delivery.
Immune system
His own system is still immature, so to make up for this he receives antibodies from you via the placenta. These protect him against anything that you have antibodies for, such as flu, mumps, and German measles. After he's born, he'll keep on getting antibodies from you via your breast milk.
His support system
The placenta now weighs 500g (1lb), measures 20-25cm (8-10in) in diameter, and is 3cm (just over 1in) thick, thus creating a wide area for the exchange of nourishment and waste products between yourself and your baby. There's now more than 1 litre (2pt) of water in the amniotic sac.
The hormones made by the placenta are stimulating your breasts to swell and fill with milk. These hormones also cause swelling in your baby's breasts, whether it is a boy or a girl. This will go down after birth.
Posted 30.06.2010
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