Definition
Vaginal bleeding after 24 weeks’ gestation and before labor.
Incidence
This is 4–5% of all pregnancies.
Differential diagnosis
Placenta previa (20%)
- Definition. Implantation of the placenta over the cervical os in advance of the fetal presenting part.
- Incidence. One in 200 pregnancies.
- Risk factors. Multiparity, advanced maternal age, prior placenta previa, prior cesarean section delivery, smoking.
- Classification (Figure 56.1).
- Diagnosis. Characterized clinically by painless, bright-red vaginal bleeding. Bleeding is of maternal origin. Fetal malpresentation is common because the placenta prevents engagement of the presenting part. May be an incidental finding on ultrasound.
- Note. When a woman presents with antepartum hemorrhage, pelvic examination should be avoided until placenta previa has been excluded.
- Ultrasound. Ultrasound is accurate at diagnosing placenta previa. Only 5% of cases of placenta previa identified by ultrasound in the second trimester persist to term.
- Antepartum management. The goal is to maximize fetal maturation while minimizing risk to mother and fetus. “Fetal distress” and excessive maternal hemorrhage are contraindications to expectant management, and may necessitate immediate cesarean section irrespective of gestational age. However, most episodes of bleeding are not life threatening. With careful monitoring, delivery can be safely delayed in most cases. Outpatient management may be an option for women with a single small bleed if they can comply with restrictions on activity and maintain proximity to a hospital. Placenta previa may resolve with time, thereby permitting vaginal delivery.
- Intrapartum management.
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