A 24-year-old G2P1 at 28 weeks gestation presents with regular uterine contractions (3–4 per 10 minutes) and vaginal discharge. On examination, cervix is 2 cm dilated and 80% effaced. Fetal heart rate is normal. Which is the most appropriate next investigation to assess the risk of imminent preterm delivery and guide management?

## Confirmatory Investigation in Symptomatic Preterm Labor **Key Point:** In a woman with clinical signs of preterm labor (regular contractions, cervical change), fetal fibronectin is the most specific test to predict imminent delivery and stratify risk. ### Clinical Context: Why fFN Here? This patient has **objective cervical change** (2 cm dilation, 80% effaced) and **regular contractions**, meeting diagnostic criteria for preterm labor. The next step is **risk stratification** — determining whether delivery is likely within 7–14 days to guide intensity of intervention. **High-Yield:** - **fFN positivity** at 28 weeks → ~40–50% risk of delivery within 2 weeks → warrants aggressive intervention (betamethasone, tocolytics, transfer) - **fFN negativity** → <5% risk of delivery within 2 weeks → allows selective use of corticosteroids and possible outpatient management - **Timing window:** 24–34 weeks (this patient is at 28 weeks — ideal for fFN) ### Comparison of Investigations | Investigation | Role | Why Not Here | | --- | --- | --- | | fFN | Predicts delivery within 2 weeks in symptomatic women; guides tocolytic/steroid use | **Best choice** — directly answers risk question | | Transvaginal ultrasound (cervical length) | Prognostic in asymptomatic women; less predictive once cervical change is evident clinically | Patient already has clinical cervical change; ultrasound adds little | | Maternal serum progesterone | No established role in diagnosis or risk stratification of preterm labor | Not validated for acute preterm labor management | | Amniotic fluid culture/gram stain | Indicated only if intrauterine infection (chorioamnionitis) is suspected (fever, maternal leukocytosis, fetal tachycardia) | No clinical signs of infection; premature invasive testing | **Clinical Pearl:** A negative fFN in this symptomatic patient would be reassuring and might allow discharge home with close follow-up, whereas a positive result would justify hospitalization and intensive fetal monitoring. **Mnemonic: fFN RISK** — **R**isk stratification, **I**mminent delivery prediction, **S**ymptomatic women (24–34 weeks), **K**ey test for tocolytic/steroid decisions.