Pelvic Pain During Pregnancy: Crossed Legs & Biomechanics

Question
Hello,
In one of you're answers to a question about pelvic pain during pregnancy you stated "Don't sit with crossed legs, one leg across the other, or with both legs tucked to the side." I was wondering why you suggest not to sit crossed legs when so many prenatal yoga instructors suggest that pregnant women sit in this manner. Would you please explain the bio mechanics of the pelvis and it effects on the baby when a pregnant woman sits crossed legged. Thank you so much.

Answer
Great question. There is a lot of conflicting information about these types of positions, both in exercise/yoga and everyday activities.

The crossed legs position when seated on a chair, places tensile, or stretching forces on the sacroiliac joint on the side of the crossed leg.

Many common yoga positions such as the tailor position, all lotus positions, pigeon pose, many seated twists, some supine twists, and Pilates "mermaid" positions, place tensile forces on the joints of the pelvis.

During pregnancy, our bodies produce hormones that soften and lengthen ligaments, so that the pelvic outlet can expand as the baby is born. Because of ligament laxity, all pregnant women should be careful never to stretch ligaments (ligaments hold out joint in proper alignment) to prevent injury, joint instability and pain.

When the pelvis becomes misaligned during pregnancy, this can contribute to/ or prevent turning of, a breech presentation.

I love yoga, and think that it's a great form of exercise during pregnancy, but specific modifications need to be made to insure safety.