Causes of Bleeding in Late Pregnancy

Vaginal bleeding occurring from the 24th week of pregnancy and prior to the birth of the baby is termed antepartum haemorrhage (APH). There are a number of causes of bleeding in late pregnancy:

Placenta praevia

Placenta praevia occurs when the placenta is implanted wholly or in part into the lower segment of the uterus. If the cervical os is completely covered it is considered a major praevia (complete) and if not, then it is considered a minor praevia (marginal).


  • The incidence is 0.48% with a resulting mortality of 0.03% [17]
  • The exact pathophysiology is unknown; uterine scarring, multiparity, multiple gestations and advanced maternal age are all associated
  • Bleeding is a result of contractions and cervical effacement and dilatation separating the placenta from the uterus
  • Prior to labour this may be self-limiting
  • Painless haemorrhage or foetal malpresentation in late pregnancy are classical signs. Abdominal pain can also occur
  • Antenatal screening at 20 weeks enables detection and expectant management
  • Women who have had a bleed will be managed as in patients from 34 weeks. Asymptomatic women may be managed as outpatients with close monitoring [16]
  • It is rare to have an undiagnosed placenta praevia present to the ED.

Placental abruption

Placental abruption is the complete or partial premature separation of a normally implanted placenta from the uterus causing haemorrhage into the basalis decide. Placental abruption should be considered when the pain is continuous. Labour should also be considered if the pain is intermittent.

  • Increased maternal age, smoking, use of cocaine, hypertension, multiple pregnancy, high parity, prolonged rupture of membranes and trauma are all associated
  • The primary cause for abruption remains unknown except in cases of trauma
  • Clinically, fundal tenderness is associated with vaginal bleeding. Bleeding may be concealed in up to 20%. Foetal distress is indicative of abruption and foetal death is common where separation is more than 50% [18]
  • DIC occurs in 10%, which can cause long-term renal failure

Vasa praevia

Vasa praevia is a condition in which the fetal blood vessels run freely and unsupported through the membranes, over the cervix across the internal os beneath the presenting part, unprotected by placenta or umbilical cord [19].

  • The incidence is approximately 1/2500 deliveries and undiagnosed is associated with a perinatal mortality of 56% [19, 20]
  • Risk factors include placenta praevia, multilobed placenta, velamentous insertion of the umbilical cord, multiple pregnancies and IVF pregnancies
  • The fetal blood vessels may be ruptured at amniotomy, spontaneous rupture of membranes or during cervical dilatation
  • Painless PV bleeding and foetal heart activity abnormalities are common. Pulsating vessels on vaginal examination are indicative, however PV examination is normally contraindicated because of the possibility of placenta praevia
  • Targeted screening of high-risk pregnancies is suggested [21].  Routine screening is not cost effective and undetected ‘low risk’ pregnancies may present to the ED

Placenta accreta

Placenta accreta is abnormal adherence of the placenta to the uterus. It is strongly associated with previous caesarean sections and can be identified on US. It is usually a post partum phenomenon although rarely may cause spontaneous uterine rupture and massive intraperitoneal haemorrhage [22].

Points to note:

  • Vasa praevia and uterine rupture are rare
  • placenta accreta is increasing in incidence with increasing caesarean section rate.
  • No definite cause can be identified in at least half of cases of APH.
  • Health professionals should be aware that domestic violence in pregnancy may result in APH. This should be screened for, especially in cases of women who present several times with APH [27]
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