It was long believed that pregnant women should lie on their left side. They thought it improved the feto placental circulation by reducing aorto-caval compression by gravid uterus.
But the truth was that this remained unproven. counter arguments can be:
- woman whose circulation is affected will feel uncomfortable and dizzy. She will spontaneously turn, without any instructions to do so.
- the circulatory effects were demonstrated in test conditions, like in anaesthesia, which may not be the case in normally sleeping woman
- if the sleeping position improved the pregnancy outcome, natural selection would have favoured laterally sleeping women, or at least those who turn to side in pregnancy.
the original article
All media highlightened this.
But the recommendation is still that, pregnant need not be adviced to lie in any particular position.
The above study is a retrospective poorly controlled study.
- NHS : Mother's sleeping position and risk of stillbirth
- bmj editorial
- Evidence from Danish national birth cohort