Subcutaneous Terbutaline (250 mcg) Recommended as First-Line Acute Tocolytic for Intrauterine Fetal Resuscitation

Uterine contractions can induce fetal hypoxic stress by repeatedly occluding maternal spiral arterioles or compressing the umbilical cord, disrupting blood flow. This transient but repeated oxygen deprivation increases the risk of decompensation in high-priority fetal organs like the heart and brain, potentially leading to anaerobic metabolism, neurological injury, and perinatal death. Current standard care often falls short in rapidly reversing this acute hypoxia. Immediate myometrial relaxation via acute tocolytics is crucial to restore fetal oxygenation, maintain aerobic metabolism, and prevent severe outcomes, addressing a critical gap in managing acute fetal distress.

This comprehensive review synthesized current evidence on acute tocolytics for intrauterine fetal resuscitation at term. It systematically addressed the indications (why), optimal timing of administration (when), ideal tocolytic agents (what), appropriate routes of administration (how), and associated side effects and contraindications (why-not). The authors evaluated commonly used acute tocolytics, including beta-sympathomimetics, nitric oxide donors, and oxytocin antagonists, considering their distinct mechanisms of action and maternal side-effect profiles to formulate best practice recommendations for clinical application.

The review strongly recommends 250 mcg of subcutaneous terbutaline as the first-line acute tocolytic for intrauterine fetal resuscitation. Alternatively, another beta-sympathomimetic such as intravenous fenoterol is also suggested. These agents are indicated for eliminating uterotonic-induced excessive uterine contractions to facilitate normalization of the fetal heart rate, allowing continuation of labor in anticipation of vaginal birth. They are also crucial for rapidly improving fetal condition immediately prior to an emergency cesarean section, particularly in scenarios like umbilical cord prolapse or chronic hypoxia when a delay in birth is anticipated. The primary goal is to rapidly restore oxygenation to fetal central organs, maintaining aerobic metabolism and avoiding the onset of neurological injury and/or perinatal death. > The timely administration of acute tocolytics helps maintain aerobic metabolism in high-priority fetal central organs, significantly reducing the likelihood of adverse fetal outcomes.