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Every year, thousands of pregnant women hear a phrase that sounds harmless but isn’t: “low-lying placenta.” Doctors call this placenta previa. In most cases, if it’s caught early and managed the right way, mom and baby do just fine. But when a doctor misses it, ignores the warning signs, or fails to plan for it, placenta previa can cause sudden, massive bleeding that puts both lives at risk.
At Snyder & Wenner, we’ve spent over 40 years representing Arizona families who were harmed when a doctor didn’t order the right test, misread an ultrasound, or brushed off a mother’s bleeding as “nothing to worry about.” This article explains what placenta previa is, why early diagnosis saves lives, and what red flags might mean a doctor fell short of the care your family deserved.
During pregnancy, the placenta grows on the wall of the uterus and acts like a lifeline, passing oxygen and nutrients from mother to baby through the umbilical cord. Normally, the placenta attaches near the top of the uterus, well above the cervix — the narrow opening at the bottom of the uterus that the baby passes through during birth.
In placenta previa, the placenta attaches low in the uterus and covers part or all of the cervix, like a doormat blocking a doorway. Doctors classify it by how much of the cervix is covered:
| Type | What It Means |
|---|---|
| Complete (total) previa | The placenta completely covers the cervix. |
| Partial previa | The placenta covers part of the cervix. |
| Marginal previa | The placenta touches the edge of the cervix. |
| Low-lying placenta | The placenta sits close to the cervix but doesn't touch it. |
Placenta previa shows up in roughly 1 out of every 200 pregnancies at delivery, though it’s found far more often earlier in pregnancy because the placenta usually “moves” away from the cervix as the uterus grows — a process doctors call migration. The risk goes up with things like a prior C-section, carrying twins or more, being over age 35, and smoking. Studies show the risk climbs from about 1% after one prior C-section to nearly 4% after five — which is exactly why obstetricians are trained to watch high-risk patients closely.
The cervix has to open during labor and delivery. If the placenta is sitting over it, labor — or even a routine vaginal exam — can tear the placenta and trigger sudden, heavy bleeding. This bleeding can starve the baby of oxygen and send the mother into shock within minutes. Placenta previa is one of the leading causes of severe bleeding in the third trimester of pregnancy, and in cases where it becomes catastrophic, hemorrhage is responsible for the vast majority of deaths.
The numbers tell the real story of what changed — and why early diagnosis is the reason it changed:
That dramatic drop didn’t happen by accident. It happened because ultrasound made it possible to diagnose placenta previa weeks or months before delivery, giving doctors time to plan a safe, scheduled C-section instead of reacting to an emergency. When that early-warning system fails — because a test wasn’t ordered, a result was ignored, or a follow-up scan never happened — families can find themselves living through the kind of emergency modern medicine was supposed to have already prevented.
of deaths in severe, untreated placenta previa cases are caused by hemorrhage (severe bleeding)
pregnancies are affected by placenta previa at the time of delivery
The classic sign of placenta previa is painless, bright red vaginal bleeding in the second half of pregnancy, often starting suddenly with no warning. This is different from placental abruption, another serious complication, which usually comes with pain and cramping. Because previa bleeding doesn’t hurt, some patients — and unfortunately some providers — mistake it for “spotting” and don’t take it seriously enough.
Many women with placenta previa have no symptoms at all before it’s found on a routine ultrasound. That’s exactly why the scan matters so much: symptoms can’t be relied on to catch this condition. The test has to do the job.
| Prior C-Sections | Estimated Previa Risk |
|---|---|
| 1 prior C-section | ~1% |
| 3 prior C-sections | ~2.8% |
| 5 prior C-sections | ~3.7% |
Other risk factors include a mother’s age (35 or older), carrying multiples, a history of previa in an earlier pregnancy, and smoking during pregnancy. A doctor who knows a patient has one or more of these risk factors is expected to pay closer attention to the placenta’s location on ultrasound — not treat it as routine paperwork.
The standard of care in modern obstetrics is built around catching placenta previa long before it becomes an emergency. Here’s what that process should look like:
18–20 Week Anatomy Scan
A routine ultrasound checks the baby’s development and notes exactly where the placenta has attached.
Follow-Up Ultrasound
If the placenta is low-lying or previa is suspected, a transvaginal ultrasound confirms it and a repeat scan around 32–36 weeks checks whether it has moved.
Delivery Planning
If previa persists into the third trimester, doctors schedule a planned C-section, typically around 36–37 weeks, before labor can start on its own.
Transvaginal ultrasound is remarkably reliable for this diagnosis — studies show it catches roughly 90% of true cases (sensitivity) and correctly rules out the condition about 98% of the time (specificity) when it’s not present. In other words, this isn’t a gray area of medicine. The tools to find placenta previa accurately have existed for decades.
Good news for most patients: roughly 90% of placentas that appear low-lying at the 18–20 week scan move safely away from the cervix by the third trimester as the uterus stretches and grows. This is exactly why the follow-up scan matters — a doctor can’t assume an early finding will resolve on its own without checking again later in pregnancy.
Placenta previa is rarely fatal when it’s caught and managed correctly. The tragedies happen when a step in that three-part process above gets skipped, rushed, or ignored. In our experience reviewing birth injury cases, the failures tend to fall into a few recurring patterns:
Common Ways Placenta Previa Is Missed or Mishandled
The consequences of these failures can cascade quickly. Uncontrolled bleeding can require emergency blood transfusions, an emergency hysterectomy to stop the hemorrhage, and starve the baby of oxygen — sometimes leading to stillbirth, permanent brain injury, or the death of the mother. Even in cases that are eventually managed, research on placenta previa pregnancies shows real risk: one tertiary care study found a perinatal mortality rate of nearly 10% and a NICU admission rate of almost 40%, numbers that underscore just how much is riding on early, careful management.
There’s also a related and even more dangerous condition called placenta accreta spectrum, where the placenta grows too deeply into the uterine wall. It’s far more common in women who have both placenta previa and a history of prior C-sections. When it’s identified ahead of time through imaging, doctors can plan a highly controlled surgical delivery with a specialized team on standby. When it’s missed, it can turn a routine delivery into a life-threatening surgical emergency with massive, sudden blood loss.
Researchers who study maternal deaths linked to severe placental conditions have reached a sobering conclusion: nearly all of them are preventable, because the imaging tools needed to catch the danger early already exist. The tragedy is when those tools aren’t used in time.
The single biggest factor separating a safe delivery from a medical emergency is time. When placenta previa is diagnosed weeks in advance, the care team can schedule a planned, controlled C-section with blood products ready, a full surgical team on hand, and no labor contractions putting stress on the placenta. When it’s missed, the same condition can present as a sudden, unpredictable hemorrhage in an unprepared delivery room.
This is why the drop in maternal mortality over the last century — from roughly 1 in 10 mothers to a small fraction of a percent — is almost entirely a story about early diagnosis, not about the underlying condition becoming less dangerous. The condition itself hasn’t changed. What changed is that ultrasound now lets doctors see the problem coming and prepare for it. That means when something still goes catastrophically wrong today, it often points to a breakdown in that early-warning system — a missed scan, an ignored result, or a delayed response.
Can placenta previa go away on its own?
Often, yes. When a low-lying placenta is spotted at the 18–20 week scan, it moves away from the cervix on its own in roughly 9 out of 10 cases by the time the third trimester arrives. This happens because the lower part of the uterus stretches as the pregnancy grows, effectively pulling the placenta upward with it. This is also exactly why a single early ultrasound is not enough on its own — a doctor has to schedule and actually perform the follow-up scan to know whether a patient is in the 90% who resolve or the smaller group who still needs a planned C-section.
Is placenta previa the same thing as placental abruption?
No, and the difference matters. Placenta previa means the placenta is covering the cervix. Placental abruption means the placenta is tearing away from the uterine wall too early. Abruption usually causes belly pain, cramping, and a firm, tender uterus along with bleeding, while classic previa bleeding is bright red and painless. Both are emergencies, but they call for different management, so telling them apart quickly matters.
How is placenta previa treated?
There is no way to move the placenta back into place. Instead, “treatment” means careful monitoring: repeat ultrasounds, pelvic rest (no intercourse or vaginal exams once previa is suspected), steroid shots to help the baby’s lungs mature if an early delivery becomes necessary, and a scheduled C-section timed to avoid labor altogether. If heavy bleeding happens before the planned delivery date, hospitalization and an emergency C-section may be required.
Can a woman with placenta previa deliver vaginally?
No. Because the placenta blocks the baby’s exit path, vaginal delivery would tear the placenta loose and cause life-threatening bleeding for both mother and baby. A cesarean section is required. This is precisely why knowing about the diagnosis well before labor begins is so important — it allows the delivery to be planned as a controlled surgery instead of a crisis.
What happens if placenta previa isn’t discovered until labor has already started?
This is the worst-case scenario the entire screening process is designed to avoid. Labor contractions can tear a previa placenta and cause sudden, severe hemorrhage with no time to prepare blood products, alert a surgical team, or transfer the patient to a facility equipped to handle it. What could have been a calm, scheduled surgery instead becomes a race against the clock, with a real risk of hysterectomy, oxygen deprivation to the baby, or death.
If you or someone you love suffered a serious hemorrhage, an emergency hysterectomy, a stillbirth, or a birth injury after a placenta previa diagnosis was delayed or mishandled, it’s worth having the medical records reviewed. Some warning signs worth flagging to an attorney include:
Questions Worth Asking About Your Care
These questions don’t automatically mean malpractice occurred — every pregnancy is different, and even well-managed cases can have bad outcomes. But when the standard screening steps were skipped or a clear warning sign was ignored, that’s exactly the kind of gap our firm investigates.
Concerned About How Your Pregnancy or Delivery Was Managed?
Snyder & Wenner has represented Arizona families for over 40 years in birth injury and medical malpractice cases, including cases involving delayed diagnosis of placenta previa. Our case reviews include in-house medical insight to help identify where care may have fallen short. Consultations are free, and you pay nothing unless we win your case.
Or visit www.snyderwenner.com to request a free consultation online.