A pregnant runner should not participate if it is a very hot day, or if she tends to be compulsive and knows that she may not be able to hold herself to a reasonable pace. Developing a relaxed attitude can be quite a learning experience. I tend to be an unreasonably fast starter in my non-pregnant races. I recently ran a four mile road race while four months pregnant. Consequently, I ran the first mile 45 seconds slower than usual.
Relaxation is an important aspect of running-and even more so during pregnancy.
Stretching is helpful, but must be performed with caution. The pregnant woman's body prepares for delivery by providing the ligaments and joints with greater stretching ability so as to facilitate the passage of the baby at birth. This increased laxity makes the joints and ligaments more susceptible to injury. Furthermore, the center of gravity shifts, so it becomes easier to fall or take a bad step which could result in sprain or injury to Mom or Babe. Increased calories are needed by all pregnant women, and even more so by the pregnant runner.