**3.4. Cyclooxygenase inhibitors**

Indomethacin is considered a first-line drug for acute preterm labor in multiple pregnancy by the ACOG [7], once it is known its efficacy in postpone delivery by at least 48 hours after initiated the treatment.

However, it is important to be aware of adverse effects related to indomethacin. During treatment period, the mother is at higher risk of gastritis, esophageal reflux, and platelet dysfunction. And, the major risk is the premature constriction of the ductus arteriosus of the fetus and oligohydramnios due to reduction of fetal renal blood flow [43, 44].

If necessary, indomethacin can be administered for a maximum period of 48 hours and should be avoided after 32 weeks of gestation; when these complications are more common, it is important to notice that before 32 weeks the risk decreases, but is not zero [37, 41].

Loading dose recommended is 100 mg per rectum and then 25 mg orally every 6 hours up to 48 hours [40].
