Pregnant women who regularly take aquarobics classes are far less likely to need pain relief during labour, research out today suggests.

A study found that only 27% of women who did aquarobics three times a week during pregnancy requested pain relief compared with 65% of those who did not.

Researchers also found that water aerobics was a safe form of exercise for mother and baby.

Experts from the University of Campinas in Sao Paulo, Brazil, divided 71 women into two groups for the study, published in the journal Reproductive Health.

All the women were less than 20 weeks pregnant at the start of the study and were healthy. The first group of 34 women undertook 50 minutes of aquarobics three times a week in an indoor pool during their pregnancy.

Meanwhile, the second group, of 37 women, did not do any regular physical exercise during their pregnancy.

All the women were closely followed up until the time of delivery and had their oxygen level, heart rate, physical fitness and skin temperature regularly measured.

Their babies were also monitored after birth.

The authors noted there was no difference between the groups in terms of how long their labour lasted or whether they required a Caesarean section.

They concluded: "The regular practice of moderate water aerobics by sedentary and low-risk pregnant women was not detrimental to the health of the mother or the child.

"There was no influence on maternal cardiovascular capacity, duration of labour or type of delivery; however, there were fewer requests for analgesia during labour in the water aerobics group."

There has been debate about whether pregnant women should exercise, with concerns raised about interference with the needs of a growing baby.

However, lead researcher Rosa Pereira said: "We've shown that the regular practice of moderate water aerobics during pregnancy is not detrimental to the health of the mother or the child. In fact, the reduction in analgesia requests suggests that it can get women into better psycho-physical condition."