Position is important even for healthy pregnant women with no risk factors say midwives on new study, said the authors of the study.
The Royal College of Midwives said the study findings were “interesting” and provided “clear lessons” for maternity staff.The Auckland University researchers found that lying face up while pregnant can change the baby’s heart rate and activity state, suggesting the foetus adapts by reducing its oxygen consumption.
The researchers monitored the foetal and maternal heart rate for 29 healthy pregnant women in the third trimester, while changing and maintaining maternal positions for 30 minutes at a time.
The “foetal behavioural state” – a measure of foetal health – was recorded for each maternal position. Each woman was followed until delivery and all babies were born in a healthy condition.
The researchers found foetal state 1F – defined as “quiet sleep” – was more likely to occur in maternal supine or right lateral positions.
In contrast, foetal state 4F – defined as “active awake” – was less likely to occur when the woman lies supine or semi recumbent.
Foetal state change was also more likely when the woman was supine or semi recumbent, said the study authors in the Journal of Physiology
In addition, they found foetal heart rate variability was affected by maternal position, with variability reduced in supine and semi recumbent positions.
Louise Silverton, director for midwifery at the RCM, said: “This is an interesting study that provides some clear information regarding maternal position and its effects of the foetus in late pregnancy.
“We have known for a long time that blood pressure is reduced where a woman is lying on her back,” she said. “Many women will say that they don’t lie on their backs as they feel ‘funny’.
“Women are advised not to sleep on their backs. Also, it is known that, when in labour, moving a woman to her left hand side may improve the foetal heart rate trace,” said Ms Silverton.
“What this study shows that is different is, that even in the healthiest of women with a foetus with no known risk factors, position is important,” she said.
She added: “There is a lesson here for midwives in that we must ensure that we advise women on the best positions for sleep as well as for lying on a sofa.”
Hannah Knight, from the Royal College of Obstetricians and Gynaecologists (RCOG), said: “This is not the first piece of research to suggest a possible link between a mother’s sleeping position and stillbirth risk. This study suggests that in late pregnancy, the heart rate of a foetus can change when a mother’s position changes.
“It is not possible to draw a firm link between maternal position and stillbirth risk from this study and further robust research is needed,” she said. ”Women should sleep in a position that is comfortable for them, and many find that sleeping on their side is the most comfortable.”