The fingertips are prominent and the fingers still quite short. Each finger is separate and moves independently of the rest. This is the most comfortable position for the hand, with the thumb and fingers outstretched rather than curled into a fist.
By now, your baby may be active for up to five minutes at a time. In the next few weeks, you may begin to feel some slight fluttering movements, particularly if this is not your first pregnancy (see You are 17 Weeks and 1 Day). You'll only be aware of those movements that cause your baby to make contact with the inner muscular wall of your uterus.
The placenta itself can act like a cushion absorbing the impact of all but the strongest of the baby's movements. For this reason, women with an anterior placenta (one lying on the front wall of the uterus-that closest to the skin) often feel the movements at a much later stage than those with a posteriorly sited placenta (one that lies closer to the back).
Your baby's brain is continuing to develop. The nerve cells that will form the outer gray matter start centrally within the brain, and need to move outward to their final position. This process takes place in waves that occur from 8 to 16 weeks. The migration process is not complete until 25 weeks and electrical activity cannot be detected until 29 weeks. Even after this point, gray matter continues to mature and organize neural connections in the brain throughout the pregnancy. Your baby's body is now longer than her head for the first time.
Tanning beds expose you to ultraviolet light which can prevent you from absorbing folic acid, which the baby needs for development. Also, it's been reported that a rise in the mother's temperature, which can happen on a tanning bed, in a hot tub or sauna, may increase the fetus's temperature. A temperature above 102° F (39° C) has been associated with spinal malformations in developing babies, and if a rise in temperature is maintained long enough, it may cause brain damage. The temperature of the amniotic fluid can also increase and it's thought that an extreme rise in your temperature can cause problems with the flow of blood to the baby. So avoid tanning beds and hot tubs while you're pregnant.
Excerpted from Pregnancy Day by Day.
Copyright Â© 2009 Dorling Kindersley Limited.
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