Progesterone Decreases the Risk of Preterm Birth
The correct answer is B - Give progesterone. Progesterone supplementation is the only evidence-based intervention among the options listed that reduces the risk of preterm birth in appropriately selected patients.
Why Progesterone Works
Progesterone is effective for preventing preterm birth in two specific high-risk populations:
Women with prior spontaneous preterm birth: 17-alpha-hydroxyprogesterone caproate (17P) 250 mg IM weekly from 16-20 weeks until 36 weeks reduces preterm birth <37 weeks (RR 0.66; 95% CI 0.54-0.81), preterm birth <32 weeks, and neonatal complications including intraventricular hemorrhage 1.
Women without prior preterm birth but with short cervix ≤20 mm on transvaginal ultrasound: Vaginal progesterone (90-mg gel or 200-mg suppository daily) from diagnosis until 36 weeks significantly reduces preterm birth <33 weeks (RR 0.54; 95% CI 0.30-0.98) and composite neonatal morbidity/mortality (RR 0.41; 95% CI 0.17-0.98) 1.
Critical Caveat for Active Preterm Labor
However, there is a crucial limitation: The Society for Maternal-Fetal Medicine explicitly states that progesterone has no evidence of effectiveness for symptomatic preterm labor 1. The question states the patient is "at 32 weeks with preterm labor," which suggests active labor rather than risk assessment. If this patient is experiencing active contractions and cervical change (true preterm labor), progesterone will not stop the labor process 1.
Progesterone works as prevention when started early in pregnancy (16-24 weeks), not as treatment for active labor at 32 weeks 1, 2.
Why the Other Options Are Wrong
A - High intensity exercise: This is contraindicated and potentially harmful. High-intensity exercise does not strengthen the uterus to prevent preterm labor and may actually increase the risk of preterm birth through increased uterine activity.
C - Reduce fluid intake: This is incorrect and potentially dangerous. Uterine distension is not caused by maternal fluid intake, and dehydration can actually trigger preterm contractions. This recommendation has no evidence base and could harm both mother and fetus.
D - Follow up only if pain is severe: This is dangerous and represents inadequate prenatal care. Women at risk for or experiencing preterm labor require close monitoring, not delayed follow-up. Regular assessment of cervical length, fetal well-being, and maternal symptoms is essential 1, 2.
Clinical Algorithm for This Specific Patient
If this patient is NOT yet in active labor (no regular contractions with cervical change):
- Assess cervical length by transvaginal ultrasound immediately 1.
- If cervical length <25 mm and she has prior spontaneous preterm birth: Continue or start 17P 250 mg IM weekly 1.
- If cervical length ≤20 mm and no prior preterm birth: Start vaginal progesterone 90-mg gel or 200-mg suppository daily 1.
- Consider cerclage if cervical length <15 mm with prior preterm birth 1.
If this patient IS in active preterm labor at 32 weeks:
- Progesterone will not be effective as tocolysis 1.
- Administer corticosteroids (betamethasone or dexamethasone) for fetal lung maturity - this is the only intervention proven to improve neonatal outcomes including reduced mortality, respiratory distress syndrome, and intraventricular hemorrhage 2.
- Consider tocolytics (calcium channel blockers or prostaglandin inhibitors) to delay delivery for 48 hours to allow corticosteroid administration and maternal transfer if needed 2.
- Administer magnesium sulfate for neuroprotection if delivery is imminent <32 weeks 2.
Important Pitfalls to Avoid
Do not confuse prevention with treatment: Progesterone prevents preterm birth when started early in at-risk women, but does not treat active preterm labor 1.
Do not use progesterone in multiple gestations: Multiple RCTs show no benefit of progesterone (17P or vaginal) in twin or triplet pregnancies 1, 3.
Do not switch progesterone formulations mid-pregnancy: If a woman with prior preterm birth develops cervical shortening while on 17P, continue 17P rather than switching to vaginal progesterone, as there is no evidence that switching provides additional benefit 1.