Preterm labor and delivery is one of the major public health issues facing medicine today. Preterm delivery is defined as delivery at less than 37 weeks. Early delivery accounts for 75% of newborn mortality in babies without birth defects. The incidence of this pregnancy complication has been steady, to slightly increasing, in recent decades.
Preterm delivery can result from spontaneous preterm labor, premature rupture of membranes (PROM), cervical incompetence as well as other medical complications of pregnancy. For the purposes of this discussion, I will focus on spontaneous preterm labor and PROM. Discussions on the other topics can be found throughout the Ask An OB.com.
What are the risk factors for preterm labor?
• History of preterm labor/birth with a prior pregnancy
• Multiple pregnancy
• Premature rupture of membranes
• Lower socioeconomic status, poor nutrition
• Uterine anomalies (bicorneate uterus, septate uterus)
• African American ethnicity
• Maternal infections (kidney infection for instance)
• Fetal birth defects
What are signs of preterm labor?
Unfortunately the signs of preterm labor may be very vague. Most women with complain of cramping or tightening in the abdomen. They may also have vague lower back pain. Some women can feel their contractions quite distinctly. Usually the signs of preterm labor are vague, however. Therefore women should be instructed on how to monitor for these signs of preterm labor.
How can my doctor diagnose preterm labor?
If you are having signs such as contractions or crampiness, your doctor can check your cervix to see if the cervix is dilating or shortening. They may also do an ultrasound to look at how long the cervix is, and to see if there is any signs of internal dilation. If you go to the hospital, they will probably hook you up to a tocodynometer, which is a belt they put around your abdomen, to trace any uterine activity. Alot of doctors are starting to use a "fetal fibronectin" test, which is a swab near the cervix. There are proteins that are released when the uterus is preparing for labor. If this test is negative, then you are highly unlikely to deliver in the next two weeks.
How can my doctor diagnose premature membrane rupture?
The first signs when the bag of water breaks is a "gush of fluid". Typically the fluid continues to leak. A doctor can do tests to see if it indeed looks as though you have had premature membrane rupture. This includes a speculum exam to see if fluid is coming from the cervix. In addition, the fluid in the vagina can have the acidity tested to see if it is consistent with amniotic fluid. Finally, this fluid can be examined under the microscope to see if it has signs typical of amniotic fluid. Ultrasound and dye testing can confirm the diagnosis if it remains unclear.
Can preterm labor be prevented?
Often times, no, however there has been promising new research that has given doctors some options to try to prevent preterm birth in women considered high risk for a short cervix or a history of prior preterm birth. This centers around progesterone therapy, by weekly injections or daily vaginal suppositories, and has been shown to reduce the rate of preterm delivery in patient. Please see http://www.askanob.com/recentadvances/pretermdelivery.html for a full discussion on progesterone.
What are treatments for preterm labor?
There are no absolute medications to treat preterm labor. There are a few medications that appear to slow down the labor process. One medication, namely betamethasone, which is a steroid, has been shown to improve newborn outcomes. Most importantly, if started earlier in the labor process, the tocolytics below can often slow down the contractions long enough to get betamethasone shots administered (two shots 12 or 24 hours apart). These betamethasone shots are life and death for the very premature fetus because they accelerate fetal lung maturation, and reduce complications the baby may experience in the nursery.
Typical medications used to treat preterm labor include:
• Magnesium--a more traditional medication that is given by IV and can slow the labor process. This medication is still commonly used, though it is being phased out by most physicians because of poor maternal side effects and improved effectiveness of alternative drugs.
• Calcium channel blocker--the most common being nifedipine or procardia. This medication is a pill that begins to act in about 15-20 minutes. It has been shown to delay delivery substantially and increase baby's birthweight as a result of this delay. The maternal complications are mild, and may include headache and lower blood pressure. Some doctors even keep moms on this for many weeks, and though this does seem to decrease the number of contractions a woman has, it hasn't been proven to delay delivery compared to bedrest alone.
• Indomethacin--this medication is an anti-inflammatory medication, similar to ibuprofen for instance. It decreases prostaglandin production, and we know increased prostaglandins can contribute to preterm labor. This medicine has been effective in studies at delaying delivery. These medications are very well-tolerated by moms, but there have been conflicting studies about fetal effects. Some studies show that with prolonged use the rate of low fluid, premature closing of an artery the fetus needs, and bowel infections increase. However, the data shows that with 48-72 hours of use, this medication is very safe and effective.
• Terbutaline--once a mainstay for therapy, this medication is being used less and less. It can be used if women do not appear to be in labor but are having significant contractions. It is a "beta-agonist" and therefore has significant maternal cardiac side effects.
The most important intervention for women with preterm labor is steroid therapy for the fetus and transfer of care to a facility prepared for early fetuses. Typically, two shots of a steroid called betamethasone are administered. Betamethasone has conclusively been shown to improve newborn outcomes. Betamethasone shots accelerate fetal lung maturity. For fetuses under 28 weeks they are extremely important, even life or death for the baby.
The preterm labor therapies change and evolve steadily. Hopefully in the future we will develop an effective treatments for preterm contractions to prevent preterm delivery and premature membrane rupture.
How can premature rupture of membranes be treated?
Sometimes, especially after a procedure such as amniocentesis, the bag of water can reseal on its own. If it has been a spontaneous premature rupture of membranes, this usually does not occur. This may have occurred because of infection, or infection can result after premature membrane rupture. Antibiotics can be shown to prolong pregnancy, and they should be given if rupture occurs less than 34 weeks. If rupture occurs over 34 weeks, because of the risk of infection, delivery is probably safest for the baby.
The benefits of betamethasone are less known in PROM. Betamethasone, or other steroids can worsen infections. In addition, babies with early rupture of membranes tend to mature faster. General recommendations are to administer betamethasone to fetuses with rupture less than 32 weeks. If a patient has clear infections, betamethasone may be held.
What is the prognosis for my baby if I do delivery early?
That entirely depends on how early you delivery. If you are very early, less than 32 weeks, one of the most important things is getting mom to a hospital that is capable of caring for an extremely premature baby. If we are unable to do this, then your baby will probably have to be emergently taken to one of these hospitals after delivery. In general, babies begin to survive after 23 weeks. If a baby is born between 23-28 weeks, the chance of survival is about 40-50% and highly depends on whether the baby has had the benefit of maternal steroid injections. In babies that do survive, about 50% have major complications. After 28 weeks, survival gradually increases and the rate of complications gradually decreases. By 34 weeks, long-term outcomes are similar to that of term babies, though they have many short-term issues.
With respect to PROM, if this happens very early, less than 24 weeks, there are additional complications. The lungs need amniotic fluid to develop properly. Therefore, if there is no fluid, the lungs cannot develop. In severe forms, this can be fatal for the baby. Also, because the fluid cushions the baby and cord, deformities especially of the face and extremities can occur, especially with very early rupture. Finally cord accidents and placental abruption are more common after PROM.
If you feel you may be having signs of preterm labor, call your doctor. Though there are many preterm labor protocols, preterm labor treatment remains one of the most difficult problems facing Obstetrics.
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