Placenta praevia

Definition

The placenta is in the lower segment of the uterus, possibly covering the cervical os.

Epidemiology

Incidence is 1 in 200 births and 1 in 1000 totally cover the os.

Pathophysiology

The placenta inserts in the lower segment. Not really anything pathophysiological about it.

Risk Factors

• Previous history
• Older mothers
• Higher parity
• Smoking
• Cocaine use
• Previous Caesarean section
• Previous spontaneous or induced abortion

Clinical Features

It is often found incidentally, on ultrasound. The most common symptom is painless bleeding after the 28th week. This bleeding tends to be profuse and sudden but typically does not last very long, meaning it is not often life-threatening. If there is coincidental abruption, there maybe some pain.

The uterus is normal on palpation but the presenting part cannot be pushed into the pelvic inlet. Spontaneous labour occurs within the following few days in 25% of cases. Vaginal exam is not indicated.

Classification

Essentially, there are grades I-IV which depend on how much of the cervical os is covered. When the cervical os is covered, it is often referred to as major placenta praevia.

Investigations

• USS - usually transabdominal, this can be done transvaginally (which is more accurate) safely.
• FBC, group and cross-matching blood may all be done depending on context.

Management

• Admission is necessary where placenta praevia is symptomatic. In major placenta praevia with bleeding, women should be admitted after 34 weeks gestation.

• Caesarean section is indicated where the placenta is <2cm from the cervical os. This should be deferred to 38 weeks gestation to minimise neonatal morbidity.

• Home management (i.e. outpatient antenatal care) is possible in placenta praevia but there are a variety of factors to consider. They should be in close proximity to the hospital and there should be somebody ready to take them to hospital at all times. Any symptoms, pain or bleeding, should be indication to take the mother to hospital.

• Cervical cerclage (stitching of the cervix) may decrease risk of premature birth

Prognosis

Perinatal mortality is 50 in 1000 and maternal mortality is low provided no vaginal examination has been performed.