History and exam

Key diagnostic factors

common

scarred uterus

Uterine scarring, usually secondary to a previous caesarean section, is a common finding.[37][44]

presence of other risk factors

Additional risk factors include advanced maternal age, smoking, previous multiple pregnancies/short inter-pregnancy intervals or miscarriages/induced abortions, prior PP, infertility treatment, and illicit drug use.

painless vaginal bleeding

Symptomatic PP typically presents as second- or third-trimester vaginal bleeding.[37][44][45]

Bleeding may range in severity, from light, moderate, heavy, to massive.

Digital vaginal examination should not be performed on women with active vaginal bleeding until the position of the placenta is known with certainty.[43]

absence of cervical/vaginal causes of bleeding on speculum examination

Very careful speculum examination may be used to exclude cervical or vaginal haemorrhage as a cause of bleeding in women in early labour with mild bleeding.

This should be done under 'double setup' to allow conversion to an immediate caesarean section in case of massive vaginal bleeding.

Digital vaginal examination should never be performed before PP is ruled out by other means.[43]

Other diagnostic factors

common

previous ultrasound anomaly in first trimester

Most occurrences of low-lying placenta found incidentally on ultrasound will resolve spontaneously as pregnancy progresses. Nevertheless, this remains an important risk factor for persistent praevia.[48]

lack of uterine tenderness

Most women with placenta praevia and bleeding will have non-tender uterus on physical examination.

Tenderness may be present if there is co-existing placental abruption or labour.

low blood pressure and tachycardia

Hypotension and tachycardia may indicate reduced blood volume secondary to haemorrhage.

However, in assessing the haemodynamic effects of bleeding it is important to remember that most young, otherwise healthy pregnant women tend to have slightly low blood pressure and to be slightly tachycardic.

Risk factors

strong

uterine scarring (most commonly due to prior caesarean section)

In the US, the frequency of placenta praevia has been increasing secondary to the increase in the use of caesarean sections. One caesarean section increases the incidence in the next pregnancy to about 0.6%.[6] Subsequent caesarean sections increase the risk slightly compared with one procedure.[6][9][11]

Although the association is weak, it is strong enough to justify a mid-trimester ultrasound to determine placental location.[6][9][10][11][24]

infertility treatments

Pregnancies resulting from IVF have about a 2% risk of placenta praevia.[30][31][32][33][34][35] Although the association is weak, it is strong enough to justify a mid-trimester ultrasound to determine placental location.

prior placenta praevia

Placenta praevia has a very slight risk of recurrence (about 0.7%).[13]

weak

advanced maternal age

Association with advanced maternal age is increasingly recognised.[12][16][17][18][19]

multiple previous pregnancies

Association with multiparity has been reported.[13][20]

smoking

Association with smoking has been reported.[13][14][21]

previous miscarriage

Association with previous miscarriage and recurrent pregnancy loss has been reported.[22][23]

previous induced abortion

Association with previous abortions has been reported.[24][25]

other placental abnormalities

Association with other placental abnormalities has been reported. These include the following:

Velamentous insertion (where the umbilical cord inserts upon the chorioamniotic fetal membranes instead of the placental mass)[26]

Succenturiate placenta (where the placenta has one or more accessory lobes).[27]

short inter-pregnancy intervals

Association with shortened birth spacing has been reported.[28]

illicit drug use

A history of maternal cocaine use, independent of tobacco use, is associated with an increased risk for placenta praevia.[29]

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