Placenta previa
The placenta is an organ that develops in the uterus during
pregnancy. In most pregnancies, the placenta attaches at the top or
on the side of the uterus. In placenta previa, the placenta attaches low
in the uterus. The placenta might partially or completely cover the
opening of the uterus, called the cervix. Placenta previa can cause
severe bleeding in the mother before, during or after delivery.
The placenta is an organ that develops inside the uterus during pregnancy. It
works to provide oxygen and nutrition to the baby and to remove waste. The
placenta connects to your baby through the umbilical cord. Typically, the
placenta is attached to the top or side of the inner wall of the uterus.
With placenta previa, the placenta attaches lower in the uterus. This results in
some portion of the placental tissue covering the cervix. It can result in
bleeding during the pregnancy or during or after delivery.
Changes in the uterus and placenta during pregnancy may lead to the problem
correcting on its own. If it doesn't, the baby is delivered by cesarean section
(C-section).
Symptoms
The main sign of placenta previa is bright red vaginal bleeding, usually
without pain, after 20 weeks of pregnancy. Sometimes, spotting happens
before an event with more blood loss.
The bleeding may occur with prelabor contractions of the uterus that cause
pain. The bleeding may also be triggered by sex or during a medical exam.
For some women, bleeding may not occur until labor. Often there is no clear
event that leads to bleeding.
When to see a doctor
If you have vaginal bleeding during your second or third trimester, call your
health care provider right away. If the bleeding is severe, seek emergency
medical care.
Causes
The exact cause of placenta previa is unknown.
Risk factors
Placenta previa is more common among women who:
Have had a baby
Have had a previous C-section delivery
Have scars on the uterus from a previous surgery or procedure
Had placenta previa with a previous pregnancy
Are pregnant after having an assisted reproductive technology (ART)
procedure for treating infertility
Are carrying more than one fetus
Are age 35 or older
Smoke
Use cocaine
Complications
If you have placenta previa, your health care provider will monitor you and
your baby to reduce the risk of these serious complications:
Bleeding. Severe, possibly life-threatening vaginal bleeding
(hemorrhage) can occur during the pregnancy, labor, delivery or in the
first few hours after delivery.
Preterm birth. Severe bleeding may prompt an emergency C-section
before your baby is full term.
Placenta accreta spectrum. Placenta previa is associated with a group
of conditions called placenta accreta spectrum. With these conditions,
the placenta grows into or through the wall of the uterus. Placenta
accreta has a high risk of bleeding during pregnancy or during and after
delivery.
