The condition of having the increased curve, called hyperlordosis, makes a woman's posture biomechanically weaker and predisposes her to chronic lower back pain. Unfortunately, the posture Aikidoists adopt when using the hara or koshi in many strong kokyu movements is also slightly hyperlordotic and stressful for the lower back muscles. So, if a woman has been actively involved in Aikido practice prior to pregnancy, and if she observes the precautions I have mentioned, she should be able to continue Aikido practice for quite a while into her term. But, if a woman has stopped training before becoming pregnant, she should not start up again during pregnancy. And even highly athletic women almost always restrict their activities drastically during the third trimester.
Women vary tremendously in the problems associated with their pregnancies.
So, pregnant women should consult with their obstetricians regarding their individual cases. Much of the information in this article was drawn from these guidelines.