Placental abruption happens when the placenta separates from the wall of the uterus before birth, and in many cases the exact cause is not known. However, several direct causes and risk factors have been clearly identified.
Direct causes
- Abdominal trauma, such as from a car accident, fall, or physical assault, can physically tear the placenta away from the uterine wall.
- Sudden or rapid loss of amniotic fluid (for example after rupture of membranes or rapid decompression with multiple pregnancy) can cause the placenta to shear off from the uterus.
Maternal health and pregnancy factors
- Chronic high blood pressure and pregnancy-related hypertension conditions (preeclampsia, eclampsia, HELLP) damage uterine and placental blood vessels and are major risk factors.
- Prior placental abruption in an earlier pregnancy significantly increases the risk of it happening again.
- Blood clotting disorders and vascular problems can impair placental circulation and predispose to separation.
Lifestyle and substance-related factors
- Cigarette smoking during pregnancy increases the risk by damaging blood vessels and reducing oxygen to the placenta.
- Use of cocaine or other stimulants (and sometimes heavy alcohol or other drug use) is strongly linked to abruption because of sudden spikes in blood pressure and vessel spasm.
Other associated risks
- Advanced maternal age, particularly over 35–40 years, modestly raises the risk.
- Multiple pregnancy (twins, triplets), polyhydramnios (excess amniotic fluid), uterine abnormalities or fibroids, and uterine infections are all associated with higher rates of placental abruption.
When to seek help
- Sudden vaginal bleeding in the second half of pregnancy, especially with abdominal pain, back pain, or frequent contractions, is an emergency and needs immediate hospital assessment.
- Anyone with the risk factors above should discuss them with a prenatal care provider to review warning signs and ways to reduce risks (such as stopping smoking and avoiding substance use).
If you are pregnant or planning pregnancy and worried about abruption, it is important to talk directly with a maternity or obstetric provider, who can assess your individual risks and advise on monitoring and prevention steps.
