Week 31 of Pregnancy

If your immune system thought your baby was foreign, it would mount an attack on him. You and your baby are designed so that this does not happen. Your baby does not have the ability to produce antibodies (which would attack you) in the uterus: he relies completely on you to protect him from infection, not only in the uterus but also after birth. Protection after birth is possible because antibodies from your immune system cross over the placenta into your baby's bloodstream, while you're pregnant. If you have immunity to a disease such as measles, mumps, polio, and many other severe infections, your baby will carry your antibodies to these conditions. This so-called passive immunity is lost with time and it is for this reason that, from two months onward, your baby will require a program of immunizations to protect against these and other illnesses.

There have been numerous studies over the past few years involving women exercising while they're pregnant. The bottom line is that exercise performed effectively and safely, at a moderate intensity and in healthy women, is beneficial.

In addition to being good for your health and making you feel more energized, exercising will get you into great shape for labor and childbirth, which is, in effect, a workout!

Here are the myths:

• Exercising will harm my baby if I move too much. Your baby is protected by amniotic fluid and nourished by the placenta. By keeping within safe exercising guidelines (see Do's and don'ts), and not doing any high-impact sports or activities where you are at risk of falling or injuries, you are not putting your baby at risk.
• Exercise will use up some of the nutrients my baby needs. Your baby's growth will be monitored at doctor appointments, so you and your doctor will be able to tell whether your baby is growing at a usual rate or whether you should increase your calorie intake. If you're concerned, increase your calorie intake on the days that you exercise.
• Doing abdominal exercises will harm the baby. You can do abdominal exercises but you should not do abdominal exercises lying on your back in the second and third trimesters. The risk of lying on your back is that the baby can press down on the vena cava (the large blood vessel that returns blood to your heart). This causes your blood pressure to fall and compromises the oxygen flow to the baby. The first sign of a problem will be feeling dizzy: if you roll on to your left side, any symptoms should disappear. Don't hesitate to consult your doctor if you're concerned. The abdominal exercises shown on page 250 give you some great ways of doing safe abdominal exercises that do not put you or your baby at risk.