How is fetal distress diagnosed?

Fetal distress—more accurately termed “non-reassuring fetal status”—is a clinical diagnosis indicating potential fetal hypoxia or acidemia, often arising from placental insufficiency, umbilical cord compromise, maternal conditions (e.g., preeclampsia or hypotension), or uterine hyperstimulation. Diagnosis relies on a combination of antepartum and intrapartum assessments rather than a single test.

Antepartum evaluation includes fetal movement counting (reduced or absent kick counts warrant further assessment), non-stress testing (NST) to evaluate baseline fetal heart rate (FHR) and reactivity, and biophysical profile (BPP) or modified BPP, which integrates NST with ultrasound assessment of fetal tone, breathing movements, gross body movements, and amniotic fluid volume. A low BPP score (<6/10) or non-reactive NST may prompt closer surveillance or delivery depending on gestational age and clinical context.

Intrapartum diagnosis centers on continuous electronic fetal monitoring (EFM). Key concerning patterns include persistent late decelerations (suggesting uteroplacental insufficiency), recurrent variable decelerations with slow return to baseline (indicating possible cord compression and emerging hypoxia), minimal or absent FHR variability coupled with tachycardia (>160 bpm) or bradycardia (<110 bpm), and sinusoidal patterns (rare but highly suggestive of severe fetal anemia or hypoxia). Importantly, isolated findings are rarely diagnostic; interpretation must consider the overall clinical picture—including maternal vital signs, labor progress, oxytocin use, and recent interventions.

When EFM is non-reassuring, adjunctive tools such as fetal scalp pH sampling or lactate measurement may be used during active labor to assess for metabolic acidosis. A scalp pH <7.20 or lactate >4.2 mmol/L supports the presence of significant fetal acidemia and often informs urgent delivery decisions. However, these invasive tests are only appropriate in select cases with adequate cervical dilation and absence of contraindications (e.g., maternal infection).

It is critical to recognize that “fetal distress” is not a standalone disease but a dynamic, time-sensitive clinical signal requiring prompt, individualized evaluation and multidisciplinary collaboration among obstetricians, midwives, and neonatologists to optimize outcomes for both mother and baby.