Treatment of Preterm Labor: NSAIDs Indomethacin
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Treatment of Preterm Labor: NSAIDs (Indomethacin)

Indomethacin for Preterm Labor

Highlights

  1. Preterm labor occurs when uterine contractions begin to open the cervix before the 37th week of pregnancy. Preterm labor can lead to a preterm delivery, which poses many risks to a baby. Doctors often try to delay preterm labor with medications called tocolytics.
  2. Indomethacin is a type of tocolytic used to stop contractions and delay the labor process. It’s a nonsteroidal anti-inflammatory drug (NSAID).
  3. Indomethacin is usually effective in delaying the labor process for 48 hours and up to seven days. This can greatly benefit the health of the baby, but using indomethacin also comes with some risks.

A normal pregnancy lasts approximately 40 weeks. While most pregnant women go into labor at the 40-week mark, some women go into labor a little earlier. Preterm labor is characterized by contractions that begin to open a pregnant woman’s cervix before the 37-week point.

If preterm labor isn’t stopped, the baby will be born early, or prematurely. Premature babies often need additional care after birth and sometimes have long-term health problems that can affect their entire lives. The earlier in pregnancy a baby is born, the more likely the baby will have physical or mental disabilities.

Doctors often try to prevent a premature birth by prescribing an anti-contraction medication called a tocolytic. Tocolytics may delay birth for several days. During that period, doctors can administer other drugs to help ensure the baby is born as healthy as possible.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a type of tocolytic. NSAIDs include ibuprofen (Motrin) and indomethacin (Indocin). Indomethacin is the most frequently used NSAID for preterm labor. It can be taken by mouth or given through a vein (intravenously). It may be used alone or in combination with other tocolytics, such as magnesium sulfate. 

Indomethacin is particularly effective in the second and early third trimesters. It may even be useful in women who continue to have contractions after being given magnesium sulfate. In most circumstances, however, indomethacin shouldn’t be used for more than two to three days at a time. 

How Does Indomethacin Work?

The effects of labor on the body are similar to those of inflammation. Labor has effects on the body that are similar to those of inflammation. When pregnant women begin to experience uterine contractions, the body starts to release increased amounts of prostaglandins and cytokines. Prostaglandins are fats produced at sites of tissue damage, and cytokines are proteins associated with inflammation. NSAIDs can prevent the body from releasing prostaglandins and cytokines, and as a result, delay preterm delivery when given at the onset of preterm labor.

How Effective Is Indomethacin?

Indomethacin can reduce the number and frequency of contractions, but this effect and how long it lasts varies from woman-to-woman. Like all tocolytic medications, indomethacin doesn’t consistently prevent or delay preterm delivery for a significant period. 

However, studies have shown that indomethacin can delay delivery for 48 hours to seven days, depending on how quickly the medication is received. This may not seem like a lot of time, but when indomethacin is administered along with steroids, it can significantly lower the risk for health problems in the baby. After 48 hours, steroids can improve a baby's lung function and increase their chances of living by 40 percent.

Indomethacin may also be used to delay delivery in women with short cervices or with excess amniotic fluid. In both of these cases, the use of indomethacin as a tocolytic agent is usually successful. However, it does come with some risks to the mother and the baby.

What Are the Possible Side Effects of Indomethacin?

For the Mother

Indomethacin causes indigestion in many women. This effect may be lessened by taking indomethacin with food or by taking an antacid. 

Other potential side effects include: 

  • dizziness
  • heartburn
  • nausea
  • vomiting
  • vaginal bleeding
  • excess amniotic fluid
  • inflamed stomach lining 

For the Baby

Indomethacin has two potentially serious side effects for the fetus. It can cause a reduction in urine that the fetus produces, and it can change the way the blood circulates through the fetus's body.

If the fetus produces a reduced amount of urine, the amount of amniotic fluid in the womb may also be reduced. Amniotic fluid is the fluid that surrounds the fetus. It is very important for the fetus’s development. The reduction in amniotic fluid seems to occur most often in mothers who use indomethacin for more than two days. During this time, amniotic fluid levels should be checked regularly by an ultrasound, which is a machine that uses sound waves to produce images of the inside of the body. The amount of amniotic fluid almost always returns to normal once indomethacin is discontinued.

Indomethacin can also cause the ductus arteriosus, a major blood vessel, to close before the baby is born. This can cause serious health problems in the baby after birth. However, the ductus usually doesn’t close prematurely when indomethacin is used for less than 48 hours. It's also less likely to be a problem before 32 weeks of pregnancy. If a mother takes indomethacin for more than two days, it’s critical to check an ultrasound of the baby's heart to make sure the blood vessel hasn’t been affected.

Other side effects that may occur in the baby include:

  • bleeding in the heart
  • high blood pressure
  • kidney problems
  • jaundice, or yellowing of the skin and the whites of the eyes

The use of indomethacin may also increase the baby’s risk of developing serious illnesses, such as: 

  • necrotizing enterocolitis, which is a serious intestinal illness
  • intraventricular hemorrhage, or bleeding in the brain
  • periventricular leukomalacia, which is a type of brain injury 

Are There Women Who Should Not Take Indomethacin?

Women who are more than 32 weeks pregnant should avoid taking indomethacin, given the potential for heart problems in the baby. Women with a history of ulcers, bleeding disorders, or kidney or liver disease should also avoid taking indomethacin. 

Since indomethacin is an NSAID, pregnant women should talk to their doctors about other risks associated with its use. Those who frequently take NSAIDs, especially over an extended period, are at a higher risk of having a heart attack or stroke. Make sure to notify your doctor if you or someone in your family has ever had:

  • a heart attack
  • a stroke
  • heart disease
  • high cholesterol
  • high blood pressure
  • diabetes 

It’s also important to tell your doctor if you smoke because smoking can increase your risks of certain health conditions.

You Asked, We Answered

  • How can I prevent preterm labor?
  • Preterm labor cannot be prevented in all cases. Though, some interventions have been studied in trials to help women deliver full term. Some tips include:

    • Always go to your prenatal appointments so that your doctor can measure your cervix.
    • Eat a healthy diet, and drink a lot of water.
    • Exercise if your doctor says it’s ok to do so.
    • Reduce stress.
    • Consider waiting to get pregnant if you had a baby 18 months ago.
    • Avoid triggers that promote preterm labor, such as certain drugs.
    • Prevent yourself from getting infections.
    • Treat medical conditions like diabetes and thyroid problems.
    - Janine Kelbach RNC-OB

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