A retained placenta is placental tissue that remains inside the uterus after birth, either as a whole organ that hasn’t detached or as fragments left behind after delivery. What it looks like depends on whether you’re asking about the physical tissue itself, the signs on the delivered placenta that suggest something is missing, or how it appears on an ultrasound. Each of these tells a different part of the story.
What a Normal Placenta Looks Like After Delivery
To understand what “retained” looks like, it helps to know what a complete placenta looks like. A healthy, fully delivered placenta is a disc-shaped organ, usually dark reddish-purple, roughly 15 to 20 centimeters across and about 2 to 3 centimeters thick. It has two distinct sides.
The maternal side, the part that was attached to the uterine wall, has a bumpy, cobblestone-like surface divided into 15 to 20 sections called cotyledons. These look like fleshy, rounded lobes separated by shallow grooves. The fetal side is smooth and shiny, covered by membranes, with the umbilical cord attached near the center and blood vessels branching outward like a tree.
After delivery, the care team inspects both sides carefully. On the maternal side, they check that every cotyledon is present and intact, like fitting puzzle pieces together. If a section is clearly missing, torn away, or ragged, that’s the strongest visual clue that tissue has been retained inside the uterus.
Signs on the Delivered Placenta That Tissue Is Missing
The most obvious sign is one or more missing cotyledons. Instead of a complete, uniform surface on the maternal side, there’s a gap or a rough, torn area where a lobe should be. The edges of the missing section often look ragged rather than smooth, indicating the tissue broke off rather than separating cleanly.
A less obvious but important sign involves blood vessels on the fetal side that extend beyond the edge of the placental disc. Large vessels running past the membrane edge suggest that a separate lobe of placenta, called a succenturiate or accessory lobe, developed away from the main disc. This extra lobe can remain attached to the uterine wall even after the main placenta delivers, and it’s easy to miss if the fetal surface isn’t inspected carefully. Torn vessels at the membrane edge are a red flag that an accessory lobe has been retained.
What Retained Tissue Looks Like Inside the Uterus
When a full placenta is retained, it’s essentially the entire organ still attached to the uterine wall. During manual removal, a clinician reaches into the uterus and feels for the edge of the placenta, then gently sweeps their hand between the placenta and the uterine wall to separate it. The tissue feels distinctly different from the uterine wall itself: softer, spongier, and slightly irregular compared to the firm muscle underneath.
Smaller retained fragments are harder to identify by feel alone. These pieces can range from a few centimeters across to tiny shreds of tissue mixed with blood clots and the decaying lining of the uterus. Over time, retained tissue can calcify, becoming harder and grittier, or it can break down and become necrotic, turning darker and softer as it degrades.
How Retained Tissue Appears on Ultrasound
Most retained placenta is identified through ultrasound rather than by direct visual inspection. On an ultrasound screen, retained tissue typically appears as a bright or mixed-brightness mass inside the uterine cavity, standing out against the surrounding tissue. This echogenic mass is the single most reliable ultrasound marker. A systematic review in the American Journal of Obstetrics and Gynecology found it had 91.5% sensitivity and 84.3% specificity for detecting retained tissue.
The appearance on ultrasound can vary considerably, though, because retained tissue is often a mix of placental fragments, blood clots, and degenerating uterine lining. Sometimes it looks like a clearly defined bright mass. Other times it appears as a more scattered, uneven collection of tissue that’s harder to distinguish from normal postpartum changes. Color Doppler imaging, which shows blood flow, can help: retained placental tissue often has its own blood supply, lighting up with color on the scan, while a simple blood clot does not.
Endometrial thickness greater than 10 millimeters after delivery can also raise suspicion, but this measurement is less accurate on its own than identifying a distinct mass.
Why the Placenta Gets Retained
There are three main reasons a placenta stays behind. The most common is a placenta that has separated from the uterine wall but gets physically trapped behind a closing cervix before it can be delivered. This is sometimes called a trapped placenta, and it involves a complete, normal placenta that simply didn’t make it out in time.
The second type is a placenta adherens, where the placenta hasn’t fully separated from the uterine wall because the uterus isn’t contracting strongly enough to shear it away. The tissue itself is normal, but the separation process stalled.
The third and most serious type is placenta accreta spectrum, where the placental tissue has grown abnormally deep into the uterine muscle. In mild cases, the invasion is shallow. In severe cases (percreta), the tissue can grow through the uterine wall entirely. This tissue cannot separate on its own because it’s physically embedded in the muscle, and it often requires surgical removal. Accreta spectrum placentas look different during surgery: there’s no clear boundary between placenta and uterine wall, and the tissue bleeds heavily when separation is attempted because the normal cleavage plane doesn’t exist.
Symptoms That Suggest Retained Tissue
If tissue remains after you’ve gone home, the signs show up in your postpartum bleeding and how you feel overall. Normal postpartum discharge starts heavy and red, gradually lightens in color over a few weeks, and eventually tapers off. Retained tissue disrupts this pattern.
Watch for heavy bleeding that soaks through a pad every hour, large clots the size of a golf ball or bigger, or bleeding that initially improves and then suddenly gets worse again. A greenish discharge or a foul smell that’s distinctly different from normal period odor can signal that retained tissue has become infected. Fever, chills, and worsening pelvic pain or cramping are other warning signs.
The timing matters too. Secondary postpartum hemorrhage, bleeding that starts after the first 24 hours, most commonly begins around 12 days after delivery. The second week postpartum is the peak window regardless of the cause, but retained tissue accounts for roughly one in five cases of this delayed bleeding.
How a Retained Placenta Is Classified
A placenta is formally considered retained when it hasn’t delivered within 30 minutes of the baby’s birth if the care team is actively managing the third stage of labor (with medication to encourage contractions). If you’re delivering the placenta physiologically, without medication, the window extends to 30 to 60 minutes. After that threshold, intervention is recommended because the risk of heavy bleeding increases significantly with time.
Retained fragments discovered days or weeks later fall into a different clinical category. These are typically found when symptoms like abnormal bleeding or infection prompt an ultrasound, and the mixed appearance of degrading tissue, clots, and possible calcification on imaging can make diagnosis more challenging than identifying a whole retained placenta at the time of birth.