During pregnancy, thanks to ultrasound we know at all times the position of the fetus, although the doctor can also know in what position he is through a vaginal examination or Leopold maneuvers.
The position of the baby at birth is of vital importance for the development of a normal delivery, so we are concerned to know at each visit, what is its position and if it evolves normally.
If the baby were pierced, if it came from buttocks or face, it could resort to cesarean delivery. On the other hand, if they tell you that the baby is in a posterior position, that is, his spine is resting on yours and presenting a part of the head that is not the crown, the delivery may be slower and with more difficulty in the descent , but be a vaginal birth.
It is not very common that the baby is crossed, but it happens, it is lying on its back and the head can have it on the left or right of the mother's abdomen. Diagonal or “shoulder” position is also rare, but both situations are usually suffered by moms who have had more than three children. 
During pregnancy, as the head of the fetus grows, it rotates inside the uterus until the skull fits into the pelvis. This usually happens from the seventh month, staying until the day of birth, especially in first-time moms. In case you have had more children, the baby can change position before birth, if it is well placed, out of place or vice versa. The reason is the distension of the uterine and abdominal muscles produced by previous births, so that the baby can move easily during the last weeks. The ideal posture of the baby to be born is in a longitudinal position, the mother and son's spine are parallel, supporting the child in the maternal abdomen, with the head down, and the crown embedded in the maternal pelvis. No studies have shown that certain exercises collaborate and help change the position of the fetus during pregnancy, but there are postures that can help in labor, such as lying on your side or face down for a few moments. But it is the specialists who will determine the best position to help your baby be born.
