The most common position of the fetus in the uterus is the vertical position. This position means that the fetal spine will be parallel to the maternal spine. In this position it will be easier for the fetus to exit the birth canal. If the baby is in the transverse position or the oblique position it will not be able to be delivered normally via the vaginal opening.
In cases like this the fetus may have to be delivered via c-section. This refers to fetal delivery through an incision in the abdomen and the uterus. Sometimes unforeseen circumstance cause c-sections to be last minute decisions but most of the time this type of delivery is scheduled in advance.
Vertical position means the fetal spine is parallel to the maternal spine thus making it easy for the fetus to go out the birth canal. If transverse or oblique, the fetus cant be delivered normally per vagina.