SMFM issues guidelines for managing patients with third trimester bleeding between 34 0/7-36 6/7 weeks.

Third trimester bleeding is not so uncommon and nearly 1 in 10 women will experience vaginal bleeding during this period. It may present as just spotting or may be heavier. It could be just due to softening and opening of cervix or a sign of more serious obstetric nightmare like placenta previa or abruption.

Optimal management of third trimester bleeding depends on accurate identification of the cause and the gestational age window.

The earlier Society for Maternal-Fetal Medicine (SMFM) recommendations were not specific to the gestational age. The recommendations were published electronically in October in American Journal of Obstetrics and Gynecology.

Recommendations: 

If a patient with placenta previa is stable and have no other obstetric complications, deliver her at 36–37 6/7 weeks of gestation. If this episode is mild and self-limiting, but there is history of previous bleeding episodes < 34 weeks, deliver her to avoid risk of major bleeding episode in future. (Grade 1B)

Routine cervical length screening for women with placenta previa is not indicated in the late preterm period because of a lack of data on an appropriate management strategy (Grade 2C)

A stable woman with placenta accreta, schedule a planned delivery between 34 and 37 weeks of gestation.  (Grade 1C)

A stable woman with vasa previa, schedule a planned delivery between 34 and 37 weeks of gestation.  (Grade 1C)

Recommendations are less clear about ideal time of delivery in placental abruption for women who are hemodynamically stable along with the fetus. Delivery may be prolonged with close monitoring of mother and fetus. If the women with abruptio is hemorrhaging profusely, she should undergo delivery.

If a woman is bleeding profusely, do not defer delivering her for the purpose of administering corticosteroids.  (Grade 1B)

Fetal lung maturity testing is not indicated in late preterm period, when a indication for delivery is already present.  (Grade 1B)

Administer antenatal corticosteroids to women who are eligible, stable and are being managed expectantly and delivery is expected within 7 days, the gestational age is between 34 and 36 6/7 weeks of gestation, and antenatal corticosteroids has not previously been given (Grade 1A).

Clinical Considerations:

For placenta previa, vasa previa or accreta, cesarean section should be performed. For other clinical situation, in absence of contraindications to vaginal delivery and fetus in stable condition, a vaginal delivery might be attempted.

Very small amount of vaginal bleeding, that resolves by the time the patient presents in the hospital, can be managed expectantly provided the patient and fetus are stable and patient has access to emergency care 24/7.

Perform an ultrasound for evaluation of cause of bleeding and location of placenta before doing a digital examination. For suspected placenta previa vaginal ultrasound is a better choice and pulsed-wave doppler may help identify a fetal arterial vessel (with FH rate) or fetal vessels with venous flow in vasa previa.

In cases of placenta accreta, ultrasound can be performed but the sensitivity and specificity is less than for placenta previa and vasa previa.

In cases of placental abruption, always rely on clinical acumen as sonography can miss the diagnosis in 20-50% of cases.

MRI is contraindicated in women with active bleeding in third trimester.

Abstract

Ultrasound is sufficient for prenatal diagnosis of placenta previa accreta: a systematic review and meta-analysis

Ultrasound is highly sensitive and specific in diagnosing placenta previa accreta, after previous cesarean section when performed by skilled sonologist reports the results of a systematic review and meta-analysis by Jauniaux and Bhide published in July issue of Obstetrics and Gynecology.

Placenta accreta is a potential life-threatening condition and requires multidiscipline involvement for successful management and reducing maternal and neonatal morbidity and mortality. Because of increasing incidence of cesarean sections, the incidence of morbidly adherent placenta is on rise.

The incidence of placenta previa accreta was 4.1% in women with 1 prior cesarean and 13.3% in women with ≥2 previous cesarean deliveries.

Prenatal diagnosis of placenta accreta allows for sufficient time and planning by involving the concerned discipline to be prepared in advance.

The researchers included data from 14 cohort studies with 3889 pregnancies presenting with placenta previa or low-lying placenta and 1 or more prior cesarean deliveries in the quantitative analysis.

There were 328 (8.4%) cases of placenta previa accreta, 90% (298 cases) of which were diagnosed with ultrasound.

Two hundred and eight patients underwent cesarean hysterectomy out of 232 cases (89.7%)

The odds of diagnosing placenta accreta were higher in prospective studies (odds ratios = 228.5) as compared to retrospective studies (odds ratio=80.8). Sonography was more accurate in diagnosing placenta accreta as the depth of villous invasion increased.

The authors stressed the need of developing screening protocols for better management of this increasingly common and life threatening obstetric complication.

Placental Accreta Index (PAI) was recently proposed to predict individual risk for morbidly adherent placenta using 2-D and color Doppler sonographic exam. It includes 5 parameters: 2 or > cesarean delivery, lacunae, myometrial thickness, anterior placenta previa and bridging vessels.

Each parameter was weighted to create a 9-point scale in which a score of 0-9 provided a probability of invasion that ranged from 2–96%, respectively. The probability of invasion increases with increasing PAI score, such that a score of 9 confers a 96% chance of histologic placental invasion.

But, the score needs further validation before it can be used as a standardized method in prediction of placenta accreta, but it definitely improved the  antenatal detection.