If a low-lying placenta is seen at the 20-week scan and the patient is asymptomatic, the patient should be rescanned at 32 or 36 weeks depending on whether placenta praevia is major or minor.
If placenta praevia is still present at the following scan, serial scans should be performed every two weeks from that point onward.
A final ultrasound is performed at 36-37 weeks to determine the method of delivery:
Elective caesarean section for major placenta praevia at 38 weeks.
If minor, then a trial of vaginal delivery may be offered. RCOG recommends that the placenta should be at least 2 cm away from the internal os for attempted vaginal delivery.
Placenta praevia carries an increased risk of obstetric haemorrhage and hysterectomy. All women with placenta praevia and their partners should have a discussion regarding complications and mode of delivery. Any decisions to decline blood or blood products should be discussed openly and documented.
Placenta praevia with bleeding (antepartum haemorrhage)
Management of an antepartum haemorrhage due to placenta praevia includes a rapid ABCDE assessment and resuscitation. Maternal resuscitation should not be delayed to determine fetal viability.
If the patient is unable to be stabilised or is in labour an emergency caesarean section is recommended.
Maternal complications of placenta praevia include:
Haemorrhage: bleeding can occur from simple trauma (e.g. intercourse) or as the cervix opens during labour due to the low-lying placenta. Additionally, there is a risk of abruption when the fetus moves into the lower uterine segment.
Hypovolemic shock secondary to bleeding
Death is rare (a major cause of death in women with placenta praevia is now postpartum haemorrhage)
Fetal complications of placenta praevia include:
Intrauterine growth restriction (IUGR)
Placenta praevia is a cause of antepartum haemorrhage (defined as bleeding > 24 weeks gestation) which occurs when the placenta overlies the lower uterine segment.
Placenta praevia can be defined as minor or major depending on placental proximity to the internal cervical os.
Risk factors include past caesarean section, previous placenta praevia, advanced age or parity, smoking, cocaine and endometriosis.
Patients can be asymptomatic or present with an antepartum haemorrhage (painless bright red vaginal bleeding >24 weeks gestation).
Ultrasound is the definitive diagnostic investigation.
Management in asymptomatic placenta praevia includes serial ultrasound scans and planning the mode of delivery (elective caesarean section) repeat ultrasound scanning and making plans for safe delivery.
Management for symptomatic placenta praevia (antepartum haemorrhage) includes a rapid ABCDE assessment and resuscitation.If unable able to stabilise or if in labour an emergency caesarean section should be performed.
Maternal complications include haemorrhage, hypovolemic shock and death.
Fetal complications include fetal haemorrhage, IUGR and premature birth.