Her Pregnancy Implanted in a Deadly Location

A woman in her early 30s had conceived through in vitro fertilization (IVF). Her rising hormone levels confirmed it.

But the pregnancy wasn’t in her uterus or fallopian tubes. It was buried next to her abdominal aorta — an implantation so rare that fewer than 50 cases have ever been reported — and had to be surgically removed.

The diagnosis, as detailed in BMJ Case Reports by Sudha Sumathy, MD, of Amrita Institute of Medical Sciences in Kochi, India, was a retroperitoneal ectopic pregnancy — one of the most dangerous and easily missed forms of ectopic gestation. It carries a mortality rate eight times higher than other abdominal ectopic pregnancies because the proximity to major vessels makes rupture potentially catastrophic.

“She felt … it was like a bomb that has been partially deactivated but still may cause harm,” Sumathy told MedPage Today.

The patient first presented with lower abdominal pain and rising β-human chorionic gonadotropin (hCG) levels 8 days after embryo transfer, but transvaginal ultrasound showed an empty uterus and no adnexal mass. Two diagnostic laparoscopies turned up nothing. Four doses of systemic methotrexate, commonly used to dissolve ectopic pregnancies, failed to bring her hormone levels down.

It was only after an MRI of her abdomen that the pregnancy was found — a gestational sac tucked in the left para-aortic region with a live embryo at nearly 9 weeks.

The two laparoscopies might not have been necessary, Sumathy said.

“Had they resorted to an abdominal [ultrasound] or a higher imaging like MRI, the second or even both could have been avoided,” she said.

Doctors then injected methotrexate directly into the sac under ultrasound guidance.

While embryonic cardiac activity was absent on repeat ultrasound at 2 weeks and the woman’s hormone levels fell to near normal, the sac persisted and surrounding tissue continued to grow. The patient developed abdominal and flank pain.

Surgery was required. An attempted laparoscopic procedure was abandoned after profuse bleeding forced surgeons to convert to open laparotomy. The sac, wedged between the renal artery and vein, was removed with an estimated blood loss of 800 to 1,000 mL. The patient recovered without complication.

In the case report, the unidentified patient said she was “in a terrible state of mind” after learning the pregnancy was near her aorta and could cause bleeding at any moment. The prospect of major surgery was frightening, she said, but the option of injecting medication directly into the sac left her “partly relieved.”

That relief was short-lived. Even after the methotrexate stopped the embryo’s cardiac activity, she said she couldn’t shake the feeling that something was still wrong — and persistent abdominal discomfort eventually sent her back for surgery. Afterward, she said, the pain and discomfort were finally gone.

The case illustrates a critical diagnostic gap, the authors noted. More than 60% of retroperitoneal pregnancies are initially misdiagnosed, and the condition can be missed even at laparoscopy. When β-hCG levels keep rising and pelvic imaging is normal, clinicians should extend their search with transabdominal ultrasound of the upper abdomen, they said.

The patient’s prior bilateral salpingectomy, performed before her IVF cycle, was a key risk factor. More than half of all reported retroperitoneal pregnancy cases have occurred in women who had their tubes removed, the authors noted.

Direct injection of methotrexate into the sac can stop fetal cardiac activity, the authors cautioned, but does not guarantee resolution. Residual trophoblastic tissue can persist, enlarge, and erode into surrounding blood vessels, causing delayed hemorrhage.

Multidisciplinary management — including obstetricians, interventional radiologists, vascular surgeons, and urologists — is essential in these cases, the authors wrote.

“Retroperitoneal pregnancies are extremely rare and may be mentioned as such for women who are advised salpingectomy prior to IVF,” Sumathy said.