What is the role of indomethacin in the treatment of preterm labor?

Updated: May 04, 2021
  • Author: Michael G Ross, MD, MPH; Chief Editor: Carl V Smith, MD  more...
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Indomethacin is an appropriate first-line tocolytic for the pregnant patient in early preterm labor (< 30 wk) or preterm labor associated with polyhydramnios. A more significant inflammatory response in the membranes and decidua is observed at gestational ages less than 30 weeks compared with 30-36 weeks. Indomethacin reduces prostaglandin synthesis from decidual macrophages. The fetal renal effects of indomethacin may be beneficial to reduce polyhydramnios.

Prostaglandin synthetase inhibitors, such as indomethacin, have been shown to have efficacy similar to that of terbutaline but are associated with infrequent maternal side effects. However, these agents readily cross the placenta and can cause oligohydramnios due to a decrease in fetal renal blood flow if used for more than 48 hours. The administration of indomethacin is often limited to 48 hours, and baseline labs, including CBC count and liver function tests (LFTs), should be ordered prior to initiation of therapy.

During treatment, urine output, maternal temperature, and amniotic fluid index (AFI) should be evaluated periodically. The initial recommended dose is 100 mg PR followed by 50 mg PO every 6 hours for 8 doses. If oligohydramnios occurs, the amniotic fluid usually reaccumulates when the indomethacin is stopped, but persistent fetal anuria, renal microcystic lesions, and neonatal death have been reported. Indomethacin can also cause premature closure or constriction of the ductus arteriosus. Since this effect is more common after 32 weeks' gestation, indomethacin therapy is not usually recommended after 32 weeks.

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