What is the appropriate initial evaluation and management for a 37‑year‑old woman at 30 weeks gestation, gravida 4 para 3, presenting with light vaginal spotting after intercourse?

Post-Coital Spotting at 30 Weeks Gestation

Immediate Management Priority

Perform transabdominal ultrasound immediately to exclude placenta previa, low-lying placenta, and vasa previa before any digital vaginal examination, as examination before imaging can precipitate catastrophic hemorrhage. 1, 2

Critical Safety Rule

• Digital pelvic examination is absolutely contraindicated until ultrasound has definitively excluded placental causes of bleeding – examination can cause life-threatening hemorrhage if placenta previa or vasa previa is present 1, 2
• Speculum examination to visualize the cervix for benign lesions (polyps, cervicitis, cervical ectropion) should only be performed after ultrasound excludes placental abnormalities 1

Initial Diagnostic Workup

Ultrasound evaluation must include:

• Placental location and exact distance from the internal cervical os – placenta previa affects approximately 1 in 200 pregnancies and is the most common cause of painless vaginal bleeding in late pregnancy 1
• Doppler assessment for vasa previa – vessels overlying the internal os carry risk of fetal exsanguination and can be subtle on imaging 1
• Evaluation for placental abruption – although ultrasound misses up to 50% of cases, identification changes management and is associated with worse perinatal outcomes 1
• Cervical length measurement via transvaginal ultrasound – a short cervix with bleeding significantly increases preterm delivery risk 1
• Assessment of lower uterine segment thickness (particularly if prior cesarean) – look for disruption of myometrium or thickness <2.5 mm suggesting uterine rupture risk 1

Most Likely Diagnosis at 30 Weeks

Post-coital spotting at this gestational age is most commonly caused by benign cervical pathology (cervicitis, polyps, cervical ectropion), but life-threatening placental causes must be excluded first. 1

• Cervical lesions are typically identified by speculum examination after ultrasound clearance 1
• Normal vital signs do not exclude significant placental pathology such as abruption, which can present with normal hemodynamics initially but rapidly deteriorate 1

Additional Laboratory Assessment

• Complete blood count – assess baseline hemoglobin and monitor for ongoing blood loss 1
• Type and screen – prepare for potential transfusion if bleeding worsens
• Rh status – administer anti-D immune globulin if patient is Rh-negative 3

Management Based on Ultrasound Findings

If placenta previa or low-lying placenta identified:

• Pelvic rest (no intercourse, no digital examinations) for remainder of pregnancy 1
• Serial ultrasounds to monitor placental location – the later in gestation placenta previa is diagnosed, the more likely it will persist 1
• Cesarean delivery planning if previa persists near term 1

If benign cervical pathology identified:

• Reassurance that post-coital spotting from cervical causes is common and not harmful to pregnancy 1
• May resume intercourse if patient comfortable, though some providers recommend pelvic rest as precaution
• Follow-up ultrasound only if bleeding recurs or increases 1

If no cause identified (approximately 50% of cases):

• Close clinical follow-up with instructions to return for heavy bleeding, severe pain, or contractions 1
• Repeat ultrasound if bleeding persists or worsens 1

Critical Pitfalls to Avoid

• Never perform digital examination before imaging – this is the single most dangerous error and can cause maternal-fetal catastrophe 1, 2
• Do not assume benign cause based on "spotting" description – even minimal bleeding can herald placenta previa or abruption 1
• Transvaginal ultrasound is safe even with placenta previa and provides superior visualization of the cervix and lower uterine segment compared to transabdominal approach alone 1