It is a common belief that when you are pregnant you should avoid any exercise and even sleeping in the supine (back) position. The theory is that the growing uterus may compress the major blood vessels to and from the heart, decrease cardiac output, result in faintness or interrupt blood/nutrient supply to the child. The majority of google searches and baby books will deliver this information. However, is this based on scientific evidence?
A review article published in the Journal of Obstetrics and Gynaecology Canada in 2007 looked into this topic. It found:
•Compared to laying on the left, a 9% fall in cardiac output when laying supine and 18% fall when standing. Therefore, laying flat is superior to standing.
•Blood flow is automatically regulated around the uterus and placenta with changes in position
•Only 4 out of 109 patients experienced light-headedness or faintness secondary to laying flat, which recovered with change in position. A second study found this in 2% of patients.
The review concluded that it is not practical to advise all women to avoid laying flat, rather to educate them that a small number of women may feel faint when laying flat and that if this occurs, change position. It also suggests that given the common discomfort and difficulty of sleeping whilst pregnant, women should adapt the most comfortable position for them. If still in doubt, speak to your Obstetrician or Midwife for further advise directly applicable to you.
During exercise, the same principles apply. Laying flat is suitable as long as the pregnant female feels comfortable. Perhaps a more common issue that should be addressed is how the female raises from this position. Performing a direct sit-up will put the abdominal muscles under excessive strain and predispose the muscles to DRAM (muscle separation). Rather the pregnant lady should roll to her side and raise to the sitting position by pushing up through her arms.
Farine, D. & Seaward, G. (2007) When it Comes to Pregnany Women Sleeping, Is Left Right? Journal of Obstetrics and Gynaecology Canada. Journal of Obstetrics and Gynaecology Canada 841-842.