Pregnant women can start physical exercise from the 12th week of pregnancy, but should make efforts to keep their heart rate to less than 150 beats per minute while doing so, the Japanese Society of Clinical Sports Medicine recommended in a report released Friday.
While exercise during pregnancy is believed to be effective in preventing weight gain and high blood pressure, excessively strenuous movement can lead to miscarriages or the impaired development of the embryo, the society's report says.
Given these factors, the doctors' group urged women to start exercising after the 12th week of pregnancy, as the risk of miscarriage declines after that. It recommended, however, that women pregnant with more than one child should refrain from exercising.
Regarding the heart rate, the group said a study carried out on more than 500 pregnant women showed that a heartbeat of over 150 in the mother sometimes caused irregularities in the heartbeat of the embryo.
It recommended swimming, walking and aerobics, but advised those not used to daily exercise to work out two or three times a week for no more than an hour each time.
The report also says sports facilities serving pregnant women should maintain close working ties with medical institutions and make it possible for users to be able to check their heart rate and body temperature.
Mitsuoki Asai, associate professor at Aichi Medical University, said, "I hope exercise facilities for pregnant women follow these guidelines."