Any problem that prolongs the second stage of labour or prevents normal delivery
The delivery of a baby, called the second stage of labour, begins as soon as the mother’s cervix has fully dilated to 10 cm (4 in) and ends when the baby is born. About 4 in 10 mothers have problems during delivery, and the risk is higher for a first pregnancy. With careful management, it may be possible to carry out a normal vaginal delivery, but if the second stage of labour is long, and the fetus’s oxygen supply becomes insufficient, there is an increased risk of fetal distress. The doctor may then carry out an assisted delivery, using vacuum suction or forceps, or a caesarean section.
Any of the problems that cause a delayed first stage of labour can prevent a normal delivery. However, even if the first stage has progressed smoothly, a problem may arise at the second stage.
Weak or ineffective uterine contractions may slow down the delivery. Pain relief, such as epidural anaesthesia during labour, may also affect the strength of contractions. If the mother is exhausted as a result of a long first stage of labour or because of poor general health, contractions may be weak and delivery may be difficult.
There may be a delay in the baby’s passage through the cervix and vagina if the baby is not in the normal position (see Abnormal presentation). Normal delivery may also be difficult if the baby cannot pass easily through the pelvis, either because the baby is large or because the mother has a narrow or irregularly shaped pelvis.
Once the baby has reached the vaginal opening, there may be problems in delivery if the surrounding tissues cannot stretch enough to let the head out.
When your cervix has dilated fully and the second stage of labour begins, your doctor will monitor the baby’s passage through the cervix and into the vagina and will check the heartbeat (see Fetal monitoring) for signs of distress. The strength and frequency of uterine contractions are monitored. This information is then used to help determine whether a vaginal delivery is possible.
If your uterine contractions are too weak, the doctor may give an intravenous drip of oxytocin, a hormone that stimulates strong contractions (see Induction of labour). When a baby is slow to pass through the cervix and vagina, the doctor may perform an assisted delivery using forceps or vacuum suction. Just before an assisted delivery, an incision, called an episiotomy, is usually made in the tissue between the vagina and the anus. This cut eases the baby’s passage and prevents the tissues around the vaginal opening from tearing. An episiotomy is also used to help delivery when a mother’s vaginal opening is too small for the baby’s head to pass through.
A caesarean section will be necessary if the baby cannot pass easily through your pelvis or if an assisted delivery would put either of you at risk.
You may feel disappointed if you need an assisted delivery, a caesarean section, or an episiotomy, but these methods are only used to ensure that your baby is delivered safely. Your ability to have normal vaginal deliveries in the future is not usually affected by any of these procedures. Many women who have a difficult first birth have no problems with sub-sequent births. However, if there is a physical reason why normal childbirth is difficult for you, such as an abnormally shaped pelvis or one that is too narrow, a caesarean birth will usually be required for future pregnancies.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.