Labor can be divided into three stages, each with a different purpose, progression, and time course. Together, these stages are called the labor curve. By monitoring your labor curve, your doctor can differentiate between what is a safe and normal labor, and what is abnormal and potentially dangerous to you or your baby. Using the labor curve to diagnose and treat labor abnormalities does not decrease the time you and your doctor have to spend in the hospital, but it makes your labor safer and more efficient, giving your baby the best possible start in life.
Before beginning a description of how labor abnormalities are diagnosed, it is useful to go over several definitions. Some of these are used interchangeably; others have very different meanings with different consequences and remedies.
- The first stage of labor is the period from the onset of labor to complete dilation of the cervix.
- The second stage of labor is the period from complete cervical dilation until delivery of the baby.
- The third stage of labor is the period between delivery of the baby and delivery of the placenta.
- Cephalo-pelvic disproportion (CPD) describes a disproportionate fetal head size in relation to the size of the mother's pelvis. This can lead to prolongation of the first or second stage of labor, which is the manifestation of CPD.
- Dystocia refers to a difficult labor or childbirth.
- Shoulder dystocia refers to labor or birth made difficult because the baby's shoulders get stuck in the birth canal.
- Oxytocin is a hormone made in the posterior portion of the pituitary gland that causes the uterus to contract. Synthetic oxytocin (also known as Pitocin) is often given to stimulate contractions.