Placenta praevia

During pregnancy, the placenta provides the growing baby with oxygen and nutrients from the mother’s bloodstream. Placenta praevia means the placenta has implanted at the bottom of the uterus, covering the cervix.

When a baby is ready to be born, the cervix (neck of the womb) dilates (opens) to allow the baby to move out of the uterus and into the vagina. When a woman has placenta praevia (the placenta has implanted at the bottom of the uterus, over the cervix or close by), the baby can’t be born vaginally. ‘Partial placenta praevia’ means the cervix is partly blocked, while ‘complete placenta praevia’ means the entire cervix is obstructed.

Some of the causes include scarring of the uterine lining (endometrium) and abnormalities of the placenta. Around one in every 200 pregnancies is affected.

Symptoms

The most important symptom in placenta praevia is painless vaginal bleeding after 20 weeks. However, there are causes of vaginal bleeding other than placenta praevia. All bleeding during pregnancy should be reported to your doctor for prompt investigation and treatment.

Why the bleeding happens

During the later stages of pregnancy, the bottom part of the uterus thins and spreads to accommodate the growing baby. If the placenta is anchored to the bottom of the uterus (as occurs with placenta praevia), this thinning and spreading separates the placenta and causes bleeding.

Sexual intercourse can also cause bleeding from the placenta praevia in later pregnancy. During labour, the cervix thins and dilates, which would normally allow the baby to exit into the vagina. In placenta praevia, the dilation of the cervix further tears the placenta and causes bleeding.

Possible complications

Some of the complications of placenta praevia include:

• Major haemorrhage (bleeding) for the mother
• Shock from loss of blood
• Fetal distress from lack of oxygen
• Premature labour or delivery
• Health risks to the baby, if born prematurely
• Emergency caesarean delivery
• Hysterectomy, if the placenta fails to come away from the uterine lining
• Blood loss for the baby
• Death.

Causes and risk factors

Some of the possible causes and risk factors of placenta praevia include:

• Low implantation of the fertilised egg
• Abnormalities of the uterine lining, such as fibroids
• Scarring of the uterine lining (endometrium)
• Abnormalities of the placenta
• Multiple babies, such as twins
• Multiple pregnancies - a woman who has already had six or more deliveries has a risk of one in 20.

Diagnosis methods

A pregnant woman who experiences any vaginal bleeding should be admitted to hospital and tested. Some of the tests used to diagnose placenta praevia include:

• Ultrasound scan
• Feeling the mother’s belly to establish the baby’s position (the baby is sideways or presenting bottom-first in around one in three cases of placenta praevia).

Digital vaginal examinations should be strictly avoided

It is sometimes difficult to tell the difference between placenta praevia and placental abruption. Placental abruption is a condition where the placenta separates from the uterine wall. Both conditions are flagged by heavy bleeding of bright red blood.

A vaginal examination is often used to help diagnose placental abruption, but could trigger heavier bleeding in the case of placenta praevia. An ultrasound scan should always be taken first, and digital (finger) vaginal examinations strictly avoided in the case of placenta praevia.

The doctor may do a speculum vaginal examination very gently to make sure the bleeding is not coming from the cervix or vagina. Once the diagnosis is made, the pregnancy needs to be very carefully monitored. Placenta praevia is a potentially life-threatening condition for the both the mother and her baby.

Treatment options vary

Treatment depends on a number of factors, including:

• Whether the placenta praevia is complete or partial
• The exact location of the placenta
• The amount of blood lost
• The gestational age of the baby
• The position of the baby
• The health of the baby
• The health of the mother.

Treatment during pregnancy

Medical treatment aims to ease the symptoms and prolong the pregnancy. Options may include:

• Bed rest.
• Hospitalisation.
• Close monitoring, such as using a fetal monitor and regularly checking the mother’s vital signs (for example, blood pressure).
• Blood transfusion for the mother.
• Avoiding any activity that triggers uterine contractions or irritates the cervix, such as sexual intercourse or orgasms.

Delivery

Once the baby is old enough to be delivered, a caesarean section is usually performed. The baby may need to be monitored in intensive care to make sure all is well. The mother will undergo a range of tests, including tests to check her blood cell counts and the clotting ability of her blood.

Where to get help

• Your GP (doctor)
• Obstetrician
• Emergency department of your nearest hospital
• Always call an ambulance in an emergency Tel. 000
• Sexual Health Victoria (SHV). To book an appointment call SHV Melbourne CBD Clinic: (03) 9660 4700 or call SHV Box Hill Clinic: (03) 9257 0100 or (free call): 1800 013 952. These services are youth friendly.