Women who swim regularly during pregnancy do not run the risk of reduced birth weight, according to a study published today in the journal Epidemiology.
There has been concern of late that certain substances in swimming pools, so-called chlorination by-products (trihalomethanes), have been linked with adverse birth outcomes by other studies.
But researchers from Imperial College, London and Bristol University investigating more than eleven thousand pregnant women in the ALSPAC study, which is based at Bristol University, found that the amount of swimming a woman did whilst pregnant did not significantly affect the birth weight of her child.
The information came from 11,462 women in the study, which is known popularly as Children of the 90s. The study has monitored the health, well being and development of over 14,000 families since the early 90s.
The study found that 59% of women never swam during their pregnancy, 31% swam up to one hour per week, while 10% swam for longer. Women who did swim were more likely to be higher educated and to be non-smokers.
Chlorination by-products are formed when water is chlorinated and the chlorine reacts with organic matter in the water. In swimming pools this organic matter may come from skin cells and body care products for example. In other countries some studies have associated these by-products with spontaneous abortion, stillbirths and birth defects but by and large these results are inconsistent and inconclusive.
There is no empirical evidence that trihalomethanes in swimming pools have a detrimental effect on the health of swimming pool users. And based on the available evidence, there is minimal, if any risk to pregnant women and the benefits largely outweigh the risks. We need disinfection to get rid of dangerous pathogens in the water and swimming as an exercise is beneficial to pregnant women and should be encouraged and enjoyed.
Notes
Nieuwenhuijsen MJ, Northstone K, Golding J and the ALSPAC Study Team. “Swimming and birth weight”. Epidemiology 2002. http://www.ncbi.nlm.nih.gov/pubmed/12410017
Please acknowledge Children of the 90s in any reporting.
ALSPAC The Avon Longitudinal Study of Parents and Children (also known as Children of the 90s) is a unique ongoing research project based in the University of Bristol. It enrolled 14,000 mothers during pregnancy in 1991-2 and has followed most of the children and parents in minute detail ever since.