NEW YORK: Long periods of bed rest could be harmful for pregnant women and may cause degeneration of their musculoskeletal and cardiovascular systems, says a new study.

The musculoskeletal system gives human beings and animals the ability to physically move by using the muscles and skeletal system. The cardiovascular system is composed of the heart, blood vessels, or vasculature, and the cells and plasma that make up the blood.

Doctors often advice women to go on bed rest if they suffer (blood) spotting, contractions before 37 weeks' gestation, high blood pressure or have a history of pre-term labour, as well as if the foetus appears to be growing abnormally. A majority of the women rest at home, while others are hospitalised, the report added.

Studies by Nasa scientists, who used bed rest to simulate weightlessness in space, found that as a result of long periods of bed rest, a person's entire musculoskeletal and cardiovascular system become de-conditioned. This degeneration begins in less than 48 hours.

The American College of Obstetricians and Gynaecologists no longer advises bed rest to prevent pre-term births because no large-scale studies have proven the method effective. Researchers recommend that women on bed rest see a physical therapist and begin a light exercise programme, if appropriate.