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[Adapted from The Joy of Pregnancy, by Tori Kropp, R.N. Copyright © 2008, used by permission of The Harvard Common Press.]

Premature Babies

A baby born prior to week 37 is considered premature. The odds of survival depend on the baby's degree of prematurity. The closer to term (Estimated Date of Confinement, or EDC) the baby is born, the higher its chances of survival. After 34 weeks of gestation with good pediatric care almost all babies will survive.

Premature babies are often afflicted by various health problems, caused by immature internal organs. Respiratory difficulties and an increased susceptibility to infection are common.

Often there is no known cause for a premature labor; however, some of the maternal risk factors may include:

• Drinking alcohol or smoking during pregnancy.
• Low body weight prior to pregnancy.
• Inadequate weight gain during pregnancy.
• No prenatal care.
• Emotional stress.
• Placenta problems such as placenta praevia.
• Various diseases such as diabetes and congestive heart failure.
• Infections such as syphilis.

Overdue Babies

[Adapted from The Joy of Pregnancy, by Tori Kropp, R.N. Copyright © 2008, used by permission of The Harvard Common Press.]

Imagine that you have passed your due date by a week or more. Your family and friends are calling to ask you if you have had the baby (as if you would have forgotten to tell them!) or, worse, why you haven't yet had the baby. You are more than ready for labor to begin!

You might need to have an induction if your pregnancy has gone two weeks or more past your due date. In this case, your baby may be quite large, your placenta may no longer be functioning adequately, or both.

A physician can induce labor by "stripping" or tearing, the membranes; by placing a synthetic prostaglandin in the cervix; by inflating a small balloon in the cervix; or by administering oxytocin intravenously.

Stripping of the membranes: Your practitioner may insert a finger through your cervix and manually separate your amniotic membranes (water bag) from the lower part of your uterus. This causes the release of prostaglandins that can sometimes initiate labor. Stripping of the membranes is often the first induction method tried.

Artificial rupture of membranes: If your cervix is "ripe" (soft and effacing) and dilated a bit, your body is quite ready for labor and perhaps just needs a jump-start. In this case, your practitioner can use a small hook to snag and break the water bag, which releases the amniotic fluid. This procedure is generally painless. Prostaglandins released in the amniotic fluid can stimulate the start of labor. Your baby's heart rate and your uterine contractions will be monitored for a period after the procedure. If contractions do not start within several hours, you may receive oxytocin.

Cervical ripening: To stimulate the softening and effacing of the cervix, physicians often use misoprostol, a synthetic prostaglandin used off-label for labor induction. A small tablet is inserted into the vagina, sometimes more than once. Often used before oxytocin, misoprostol occasionally initiates contractions by itself.

The primary danger of misoprostol is that it can cause contractions that come too frequently or last too long. For this reason, the baby's heart rate and the mother's uterine contractions are monitored carefully after the drug is administered.

Foley catheter: The practitioner may insert into your cervix a catheter with a very small, uninflated balloon at the end. The balloon is then filled with a small amount of water. This puts pressure on the cervix, and the pressure stimulates the release of prostaglandins. As the cervix dilates, the balloon falls out, and the catheter is removed.

Oxytocin Injection (such as Pitocin): The administration of a synthetic form of the natural hormone oxytocin is the most common method of inducing labor. Causing uterine contractions, this is administered in intravenous fluid in very small doses at first. Over the course of several hours or a day, the amount is gradually increased, just as a woman's production of natural oxytocin increases as labor begins. Besides causing contractions, this synthetic hormone stimulates the body to produce its own oxytocin.

The chance of a successful induction is much higher if the cervix is soft and partly effaced before an oxytocin injection is given. This is why a synthetic prostaglandin is often administered first. If labor does not begin after a full day of oxytocin injection, the drip may be stopped and restarted the following day. Most inductions are successful by the end of the second day.

Things to Remember

• The unborn baby spends around 38 weeks in the uterus, but the average length of pregnancy, or gestation, is counted at 40 weeks.
• Pregnancy is counted from the first day of the woman's last period, not the date of conception which generally occurs two weeks later.
• Since some women are unsure of the date of their last menstruation (perhaps due to period irregularities), a baby is considered full-term if its birth falls between 37 and 42 weeks of the beginning of the woman's last menstrual period.