Breech presentations

Abstract

In over 95% of pregnancies the fetus at term will present head first whether or not the expectant mother has had prenatal care. This is because the fetus in its normal attitude of full flexion fits best into the uterus in this way. This is particularly so because in the latter weeks of pregnancy the uterus undergoes painless contractions (Braxton-Hicks) which tend to make the longitudinal axis of the passenger align itself with that of the passage. The broad fetal back needs more room than the ventral surface and tends to occupy the anterior half of the uterus, as the maternal lumbar spine projects into the posterior portion of her abdomen. In the last weeks of pregnancy the head may engage in the pelvis.