When the nurse called from the delivery room, her voice was quavering—and not because she felt bad about waking me on that winter night. She was upset because she’d never seen a woman bleed so much.
As a gynecologic oncologist, I’m trained to understand how blood flows in the pelvis and how to remove growths from the blood vessels that feed the uterus. Obstetricians call me when they need help with postpartum bleeding they can’t stop. Usually the causes are simple: an artery lacerated during a cesarean section or a tear in the vagina after the birth of a large baby. But sometimes the bleeding is more unusual. This was one of those cases.
The threat was first recognized when the patient, eight months pregnant, had premature contractions and bleeding. An ultrasound revealed problems with the placenta, the mass of blood vessels that implant in the uterus, connect the fetus to the mother’s blood, and serve as a conduit for nutrients. The placenta was growing over the cervix, the opening of the birth canal. This condition, called placenta previa, occurs in roughly 5 in 1,000 deliveries. In this patient, the faulty growth was related to her previous pregnancies.
Two years earlier, the 34-year-old patient had undergone a third cesarean section. Mother and child had done well, but this pregnancy, the woman’s fourth, failed to implant in the rich lining of the upper uterus. Instead, it implanted in the scarred lower segment, over the old incision. That led to several problems. Blood vessels had difficulty penetrating the scar, and the fetus grew poorly. Expanding to compensate for the reduced blood supply, the placenta spread over the cervix, covering the opening to the birth canal.
More problems arose as the pregnancy proceeded. During any pregnancy, the uterus expands to accommodate the fetus. But the lower uterine segment, where the placenta for this pregnancy had implanted, is made of much less elastic tissue. And because the cervix is not suited for placental attachment, the implantation triggered bleeding in this patient. The blood delivered a chemical signal that stimulates contractions, which began pulling the cervix open, tearing the placenta growing above it. Her doctors stopped the contractions and the bleeding with bed rest and medication. They knew the baby couldn’t be delivered vaginally without lacerating the placenta and causing the mother to bleed to death. The obstetrician scheduled a cesarean section.
Cutting into the uterus above the placenta to deliver the baby is usually a lifesaving procedure. And it is usually uncomplicated. But in some instances the abnormal placenta goes beyond covering the cervix. It grows through the uterine lining and muscle to the outer covering of the uterus. This condition is known as placenta percreta (percreta is Latin for “grown through”). Uncontrolled bleeding can occur because the lower uterus lacks the muscle cells of the upper uterus, which would contract to stem blood loss. Usually only a hysterectomy can save the life of the mother. Even more rarely, the placenta grows through the uterine wall and into the bladder or bowel. When labor starts, the mother’s bleeding is torrential. Stopping the bleeding can require the removal of portions of the affected organs. That was what this mother and the medical staff faced. That was why the nurse’s voice was quavering.
We know little about how placental development is regulated. We do know that no baby could survive if the placenta didn’t attach to and invade the uterine lining. The placenta functions like lungs, stomach, and kidneys for the growing baby, taking in oxygen and nutrients and carrying off carbon dioxide and wastes. To do so, the growing placenta first binds to attachment proteins on the uterine lining. After the placenta attaches, it releases enzymes known as proteinases that dissolve the matrix between cells and eat through the walls of small uterine arteries and veins. Bathed in the mother’s blood, the growing embryo thrives.
To prevent the placenta from invading like a cancer, uterine tissues normally produce substances that limit its growth. But a scarred uterine wall can’t release enough inhibitory signals, so the placenta invades and destroys the uterine wall. Nourished by maternal blood vessels, the placenta can grow new, fragile vessels that account for much of the catastrophic bleeding that follows delivery.
While we don’t know enough to prevent the development of placenta percreta and related conditions, we do know that it tends to occur in older women who have had previous pregnancies. The risk for placenta percreta is also higher after a cesarean section or uterine curettage, in which tissue lining the uterus is removed. Both procedures can leave denuded scar tissue that makes poor terrain for implantation. Multiple prior pregnancies can have the same effect. So can implantation into the lower uterine segment, where the uterine wall is more fibrous than in the expansive upper uterus.
Ultrasound can reveal if the placenta is invading the uterine wall, but the extent of the invasion can be hard to interpret, especially when the placenta is growing over the cervix. Magnetic resonance imaging is more detailed, but it is rarely used to screen pregnancies. When placenta previa is diagnosed before delivery, obstetricians can plan what to do, including whether to do a hysterectomy after a cesarean. Unfortunately, most cases of the more invasive placental growth, placenta percreta, aren’t found until after the baby has been delivered. That’s when the terrible bleeding starts.
When I arrived at the operating room that night, the operating suite was relatively quiet. The obstetrician had wisely packed the bleeding pelvis with rolls of gauze: The pressure stopped the bleeding temporarily, like a finger on a cut. The anesthesia team had started large intravenous lines and had brought the patient back from the verge of shock with blood and fluids. The baby—a three-pound boy—had already gone to the pediatric intensive care unit for blood transfusion and artificial respiration. But the room showed all the signs of crisis: Equipment wrappers, torn paper, and empty bags of saline lay about. Blood was everywhere—in discarded sponges, in full suction canisters, on the gowns of the obstetrician, the resident, and the student, on the drapes, and on the floor.
Masked, scrubbed, and gowned, I waited until more units of blood were ready before I pulled the pack out of the patient’s pelvis and set to work. The volume of bleeding was tremendous—almost a pint every few minutes, we later found. It came from the back of the bladder, where the placenta had encroached upon the cervix, and from vessels against the pelvic wall that feed the pelvic organs. The bladder usually peels away readily at the time of cesarean section, allowing a low incision into the uterus. Usually the procedure is relatively bloodless because the lower uterus has fewer blood vessels than the upper portion. In this case, however, the space between the cervix and the bladder was choked with placental tissue, and it had torn during the contractions. While the resident sponged and vacuumed the blood away, the obstetrician and I first tied off the major arteries feeding the uterus, the bladder, and the rectum. But that didn’t stop the bleeding much because a pregnant uterus is so packed with blood vessels. Then we removed the bleeding tissues: We took out the uterus, then removed the back wall of the upper bladder. At last, we tied off open blood vessels, repaired the bladder, and closed. The procedure lasted four hours. I went out, squinting at the strange light of morning.
Although the patient had lost the equivalent of all her blood twice over, she did surprisingly well. Her blood loss had never progressed to full-blown shock, so her liver, heart, and kidneys were undamaged. She was walking within two days, and by the end of the week she went home. Her bladder was still healing, though, and she would have to wear a catheter for a few days longer. Her son, born premature and anemic, required transfusions, and he spent almost a week on a ventilator. But he grew quickly and went home within a month. The obstetrician took the longest to recover. Now she tells the story to her trainees, drilling them for the worst that can happen when births go bad in a hurry.
Stewart Massad is a professor of gynecologic oncology at Southern Illinois University School of Medicine in Springfield, Illinois. The cases described in Vital Signs are true stories, but the authors have changed some details about the patients to protect their privacy.
