Nancy A. Melville

April 06, 2012

April 6, 2012 (Phoenix, Arizona) — As cesarean delivery rates increase in the United States and around the world, clinicians report a significant increase in so-called "cesarean scar pregnancies," involving the implantation of a pregnancy in the site of a cesarean scar, according to research presented here at the American Institute of Ultrasound in Medicine (AIUM) 2012 Annual Convention.

The condition, referred to by a variety of terms, is still rare (representing only about 1 in 2500 pregnancies in the United States) but is potentially serious, said Ilan Timor-Tritsch, MD, a professor of obstetrics and gynecology and director of OB/GYN Ultrasound at New York University (NYU) Medical Center.

"Cesarean scar pregnancies currently represent less than 1% of all pregnancies; however the rate is definitely increasing due to the increasing cesarean section rates," he said.

"If left untreated, the condition is frequently complicated by first-trimester uterine rupture, profuse hemorrhage, and possible emergency hysterectomy."

In a literature review of 232 articles from 1995 to 2011, Dr. Timor-Tritsch found 751 reports of cesarean scar pregnancies. Among them, the diagnosis was originally missed in as many as 107 cases, or 13.6%.

The most frequent misdiagnoses were miscarriage in progress, cervical pregnancy. In most of the cases, a dilation and curettage (D&C) was performed, which resulted in massive immediate or delayed bleeding.

In a separate retrospective review looking only at cases managed at the NYU Department of Obstetrics and Gynecology, Dr. Timor-Tritsch's colleague, Ana Monteagudo, MD, said that local (intra–gestational sac) and intramuscular methotrexate in fact appeared to be the most appropriated treatment for such cases.

Among 26 patients referred to the center over the past 2 years for cesarean scar pregnancy, 19 received the injection treatments. When the pregnancies were followed for 44 to 177 days, no complications were observed.

Concentrations of quantitative β-human chorionic gonadotropin (hCG) serum showed initial increases with the treatment, but they eventually became undetectable, and gestational sac volume and vascularization also became barely detectable.

"In our practice, combined intramuscular and intragestational methotrexate injection treatment was successful in treating these cesarean scar pregnancies," said Dr. Monteagudo, a professor of obstetrics and gynecology at the NYU School of Medicine.

Dr. Timor-Tritsch's literature review, however, found an alarmingly wide variety of other treatment approaches. "[The literature showed] a whopping 31 primary treatments rendered in these 751 cases," he said. "This is unbelievable."

Complication rates, likewise, were high, with as many as 331 patients (44%) having complications.

Among patients treated with systemic methotrexate alone, the complication rate was 62%.

"If only systemic methotrexate alone was used, that yielded the most complications because it led to a secondary treatment that may have been disastrous," Dr. Timor-Tritsch said.

The use of D&C, alone or in combination, resulted in a 61.9% complication rate, and uterine artery embolization had a 46% complication rate.

Treatment with hysteroscopy had a lower complication rate of 18%.

"Hysteroscopy alone or in combination was a much better option because it directed the treatment to the specific area," Dr. Timor-Tritsch said.

And, as seen in the NYU experience, local injection of methotrexate with transabdominal or transvaginal guidance alone or in combination of intramuscular methotrexate had the lowest rate of complications, at slightly less than 10%.

Many of the complications reported in the literature review resulted because clinicians were not aware that increases in hCG concentrations could be expected with the treatment, Dr. Timor-Tritsch noted.

"Many secondary treatments were triggered not by bleeding, but by the observation of a post-treatment increase the hCG cycle and vascularity," he said. "The treatments often resulted in escalation of the critical situation and often hysterectomy."

"Knowledge of the naturally occurring increase of the hCG volume in blood vessels with a slow resolution could have avoided a secondary resolution," Dr. Timor-Tritsch said.

Transvaginal ultrasound represents the most effect diagnostic tool for cesarean scar pregnancy, the researchers say.

Key sonographic markers include the following:

  • No fetal parts in the uterine cavity or cervix;

  • A thin myometrial layer between the bladder and gestational sac;

  • A triangular-shaped gestational sac;

  • A gestational sac that is close to the bladder and uterine wall; and

  • Presentation of arteriovenous malformation in the area.

Even when clinicians do correctly diagnose a cesarean scar pregnancy, some may suspect the pregnancy will move into the uterine cavity, and Dr. Timor-Tritsch's review showed that in 9 cases, the pregnancy did in fact reach viability and repeat cesarean delivery was performed.

But those cases are by far the exception, he said.

"The most important issue to keep in mind is that the scar pregnancy behaves totally different from a cervical pregnancy. Some physicians are tempted to believe that it will slide over and grow into the cavity, and that may happen, while others say 'well, let's continue the pregnancy and, if needed, at term we'll do a hysterectomy,' but that can give false hope to the patients," he said.

Dr. Timor-Tritsch noted that several patients at NYU ended up with an emergency hysterectomy and infant death after being advised elsewhere to take a wait-and-see approach."

Theories regarding the causes of cesarean scar pregnancies include the possibility that local injury of endometrium induces and inflammatory response that prompts implantation.

The process appears similar to that seen with placenta accreta, and Dr. Timor-Tritsch suggested that the 2 may in fact be closely related.

"There seem to be striking similarities between cesarean scar pregnancy and placenta accreta, and I would suggest that the two may indeed represent a single disease — a single entity."

His review indicated that as many as 52% of the cesarean scar pregnancies occurred after only 1 previous cesarean delivery. Dr. Timor-Tritsch suggested that early precautions should be considered to prevent this.

"Early recognition of cesarean scar pregnancy and placenta accreta starts with patient education. Therefore, when you discharge your patient after cesarean section, recommend an early transvaginal sonography for future pregnancies."

"The diagnosis with ultrasound currently has a sensitivity in the literature of 80.4%, but I personally think that if the awareness increases, the number could go up to 100%," he said.

Dr. Timor-Tritsch and Dr. Monteagudo have disclosed no relevant financial relationships.

American Institute of Ultrasound in Medicine (AIUM) 2012 Annual Convention. Presented April 1, 2012.

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