The normal length of pregnancy is 37 to 42 weeks. A baby born before 37 weeks is called premature or preterm (see Premature Birth).
During labor, the baby is monitored for signs of distress, which can indicate that the baby's oxygen supply is reduced. One sign of fetal distress is meconium-stained water (meconium is the baby's first dark green bowel movement). However, this alone doesn't always indicate fetal distress, but if it's combined with a slowing of the baby's heart rate, fetal distress is more likely and steps may be taken for a prompt delivery. If there is thick meconium in the water, there is a danger that the baby could inhale meconium at birth, which can lead to breathing problems and lung infection.
Sometimes the cervix fails to dilate as expected during the first stage of labor. There are several factors that can hamper the progress of labor: the baby's head may be too large for the pelvis; there may be inefficient contractions; or the baby may not be in the right position (see Lie and presentation).
Rarely, the umbilical cord lies below the baby. This is more likely in a breech birth, or where the baby lies in a transverse position. In these cases, when the water breaks, the cord can slip through the cervix. This is an emergency because the cord may be compressed and restrict or cut off the baby's oxygen supply.
Unless an immediate assisted vaginal delivery is possible, an emergency cesarean will be done.
Shoulder dystocia is when the baby's head is born, but the shoulders remain stuck so the body cannot be born. It's more common if the baby is big or if the mother has diabetes.
If the head is delivered, and there are signs that the rest of the baby is not coming easily, the mother's legs will be lifted up to help the baby's shoulders down and an episiotomy may be done (see Episiotomies). If the baby still doesn't come easily, there are maneuvers the doctor will do to help release the shoulders and aid the delivery (see also Shoulder dystocia).
This condition is said to occur if a woman loses more than 1 pint (500 ml) of blood within 24 hours of birth. It can be due to the uterus not contracting quickly enough, to incomplete delivery of the placenta, or to vaginal tears. Active management in the delivery of the placenta (see Delivery of the placenta) makes it less likely to happen. Factors that increase the risk include a large baby or twins; prolonged labor; or bleeding before the labor.
It's often possible to control bleeding with drugs to help the uterus contract, or by correcting problems such as retained bits of placenta, or by suturing tears. If bleeding continues, arteries that supply blood to the uterus may be closed off. You may also need a blood transfusion.
Excerpted from Pregnancy Day by Day.
Copyright Â© 2009 Dorling Kindersley Limited.
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