Measurements around the head, abdomen, and thigh bones are used from the ultrasound image to estimate the weight of your baby. Interestingly, on average, boys are now starting to be slightly heavier than girls.
Your baby's muscle tone takes some time to develop fully. By this week of your pregnancy, head control is improving and in the legs muscle tone now allows for smoother and more complex movements. For once, the arms and hands lag behind the legs and feet in development, taking another three weeks to achieve the same level of tone and movement.
In the last few weeks the familiar "fetal position" is increasingly seen on scans: this is not only due to lack of space, but also because your baby's flexor muscles (those that bend the elbows, hips, and knees) have a better tone than her extensor muscles (the muscles that extend the arms and legs) in each limb.
You will also be aware that your baby is moving more now than at any other time. You only feel the movements that hit the lining of your uterus, but there will be many more small movements of which you are completely unaware. Movements inside the uterus are important: they help your baby's coordination, strengthen her bones, and increase muscle mass. The number of muscle cells increases up until 38 weeks. From this point on, individual muscle cells lengthen and expand in response to exercise, further increasing muscle mass and strength.
In a pregnancy without problems, an orgasm will not cause premature labor, and at full term orgasm will only cause the onset of labor if it's going to happen anyway. If you have had any signs of premature labor, or your water has broken (see Water breaking), you'll be advised to avoid sexual intercourse. This is because the hormone oxytocin increases during sexual arousal and oxytocin causes the muscles of the uterus to contact. Orgasm may increase practice, or Braxton Hicks', contractions.
If you've gone past your due date and are at a point when your body is ready to go into labor, then sexual intercourse may help things to start for two reasons: the prostaglandins in semen will help the cervix to soften at this stage of pregnancy, and the contractions stimulated by orgasm have more chance of developing into early labor contractions.
Here are some ideas for delicious non-alcoholic drinks:
Excerpted from Pregnancy Day by Day.
Copyright ©2009 Dorling Kindersley Limited.
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