In this side view of the embryo the spinal cord is clearly curved as it begins to develop. The pale-yellow ridgelike structures along the back are somites-your baby's developing muscular system.
Like most newly pregnant women, you're probably on the lookout for a rounded belly, but it's unlikely to make an appearance just yet. On average, the fourth month marks the greatest period of growth, with your pregnancy most definitely appearing as a rounded abdomen.
If it's not your first pregnancy, you might start to show earlier, possibly as early as eight to 10 weeks, since your abdominal muscles will be more relaxed. Conversely, women who have firm abdominal muscles may show later. If you are expecting twins or triplets, you can expect to show even earlier.
It's safe to do abdominal exercises lying on your back during your first trimester. Toward the end of the first trimester, or when you start "showing," you should stop doing abdominal exercises on your back (see Abdominal Exercises for other exercises you can do at this point).
When you are doing abdominal exercises, it's important to breathe correctly: remember to inhale to start and exhale on each effort.
The purpose of abdominal exercises is to strengthen core muscles. The deeper transverse abdominis muscle that runs horizontally across your body is vital for core stability and strength as your baby develops. The rectus abdominis muscle that runs vertically down your body is the muscle that will stretch during pregnancy and weaken, so it's vital to keep the transverse muscle strong to help your posture and support your spine.
The sooner you begin to strengthen the transverse abdominis, the better. In the first trimester, one of the exercises you can do to strengthen this muscle is shown below.
Unless you have been told by your doctor to avoid sex because of specific problems, such as a history of miscarriage or unexplained bleeding, then prenatal sex is safe at any stage. Enjoying intimacy with your partner is beneficial to your relationship.
Your baby is cushioned in fluid in the amniotic sac inside your uterus and protected by a plug of mucus at the cervix. Even deep penetration isn't harmful.
Excerpted from Pregnancy Day by Day.
Copyright Â© 2009 Dorling Kindersley Limited.
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