Friday November 21 2008
“Doing aqua-aerobics during pregnancy can ease the pain of childbirth,” reports the Daily Mail today. The newspaper bases its claims on a Brazilian study of pregnant women who did water aerobics three times a week.
Although the newspaper focused on the pain-relieving aspect of the story, the aim of the study was to investigate the effects of aerobic exercise on heart measurements (such as heart rate) in pregnancy and delivery, and whether exercise is harmful to the baby.
Women who exercised did request pain relief less often, but this result may have occurred by chance. Additionally, as this was a small study that was not designed to explore pain relief, the results cannot support such a conclusion.
The study found that exercise made no difference to the mothers’ heart measurements and had no harmful effects on the mother or baby. Therefore it supports regular mild to moderate-intensity aqua aerobics as a healthy form of exercise during pregnancy.
Where did the story come from?
This research was conducted by Erica P Baciuk and colleagues from the Departments of Obstetrics and Gynaecology and Anesthesiology, and the University of Campinas in Brazil.
The research was partially funded by a grant from the University of Campinas. The study is available as an advanced online publication, and will be published in the peer-reviewed journal Reproductive Health.
What kind of scientific study was this?
This was a randomised controlled trial examining the link between water aerobics and the cardiovascular measurements of mothers during birth, including looking at the outcomes in the newborn.
The research was further investigating the effects of lifestyle during pregnancy, as there have been previous concerns that exercise may interfere with circulation to the foetus or may increase the risk of foetal abnormalities and growth restriction.
The researchers recruited 71 women who were below 20 weeks of pregnancy, carrying a single foetus, receiving antenatal care and had no pregnancy-related risk factors.
They excluded women who exercised regularly, had had two or more previous Caesarean sections, were morbidly obese or had one of a range of disorders. These included including cardiovascular, pulmonary, neurological, endocrine or musculoskeletal disorders.
The women were randomised into two groups. One group (37 women ) took no exercise throughout their pregnancy and the other (34 women) took part in water aerobics. Water aerobics consisted of three 50-minute sessions a week. The intensity of exercise was determined by monitoring the woman’s heart rate.
The women were examined at three time points during pregnancy: at 18-20 weeks (before commencing the exercises), at 22-26 weeks and at 32-36 weeks.
Researchers examined their cardiovascular capacity using an endurance test conducted on a treadmill. Before, during and after the test they took various measures including mother’s heart rate, blood pressure, skin temperature and ECG heart tracing, and examined foetal heart rate. The test was immediately stopped if there were signs of exhaustion, or significant alterations in any of the tested measures.
After birth the investigators collected information on the duration of labour and type of delivery. Principally they looked at the mother's cardiovascular capacity and skin temperature.
As secondary outcomes they also looked at maternal heart rate, blood pressure and foetal heart rate. They looked at other features of labour including type of delivery, length of labour, request for pain relief (analgesia) and outcomes in the newborn such as birth weight and vitality.
What were the results of the study?
Cardiovascular measurements were similar for both groups of women during pregnancy. For all women, the researchers noted that oxygen consumption and physical fitness were at their peak during the second trimester assessment at 22-26 weeks. These returned to early pregnancy levels at the third trimester assessment.
In all women cardiac output (the volume of blood pumped around the body in a minute) was found to increase as the pregnancy progressed. Temperature was found to increase with exercise.
There were no differences between the two groups of women in the type of delivery, duration of labour or outcomes in the newborn. However, significantly fewer women in the water aerobics group requested pain relief (27% vs 65%; RR 0.42, 95% CI 0.23-0.77).
What interpretations did the researchers draw from these results?
The researchers concluded that the regular practice of water aerobics by otherwise sedentary, low-risk pregnant women:
- is not detrimental to the health of the mother or child,
- has no effect upon maternal cardiovascular or neonatal outcomes, and
- has no effect on the type of delivery.
What does the NHS Knowledge Service make of this study?
The newspaper has incorrectly placed emphasis on the use of pain relief mentioned in the study. The primary aim of this research was to investigate whether water aerobic exercise would have any effect on women's cardiovascular measurements during pregnancy and delivery, or have any detrimental effect on the foetus or newborn.
The study found that water aerobics did not affect cardiovascular measurements, and concludes that this type of exercise during pregnancy is not detrimental to the health of the mother or child.
The study did find that fewer women who did water aerobics requested analgesia during birth, but the study was not designed to explore this factor as a primary outcome. As such, the size and nature of this study mean we cannot have confidence that differences in requesting pain relief between the groups were not due to chance.
Other points to note about this study:
- The power of the study was reduced by the fact that researchers report that one-third of the women assigned to take part in aqua aerobics discontinued sessions, for various reasons.
- The fact that some women did not request pain relief does not necessarily mean the labour was "less painful", as The Daily Telegraph states in its headline. People can cope with different levels of pain and this may have differed between the groups.
- The study does not specify the type of pain relief that was requested. For example, the use of gas and air is not the same as complete analgesia with an epidural.
- Aqua aerobics would need to be compared to other forms of mild to moderate-intensity exercise during pregnancy. This could give a clearer indication of whether similar results would be obtained with different exercise programmes or if it is this particular form of exercise that is "not detrimental to health".
The study supports regular mild to moderate-intensity aqua aerobics as a healthy form of exercise in pregnancy.