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Abdominal pregnancy--an obstetrical enigma.

Abdominal pregnancy is defined as an IP implantation of an ectopic pregnancy exclusive of tubal, intraligamentous or ovarian permeation. (1) Its incidence worldwide varies from 1:1320 to 1:10,200 births. (1) The condition is associated with significant maternal mortality, with rates reported in the literature from 0.5 to 30%, and a perinatal mortality rate of approximately 95%. (2,3)

In 1876, John Stubbs Parry was the first to present an authoritative treatise on abdominal pregnancy. He characterized it as an anomaly that had no parallel in the history of human injury and disease. So the question can be posed--what has really been accomplished during the last 130 years in elucidating the etiology, diagnosis and treatment of abdominal pregnancy?

To date, no specific etiologic factor accounts for the occurrence of the disease. The categorization of the condition is varied. An older system subdivides abdominal pregnancies into primary or secondary types. Primary abdominal pregnancy is characterized according to the following anatomic conditions: 1) normal tubes and ovaries, 2) absence of a utero-placental fistula, and 3) attachment exclusively to a peritoneal surface early enough in gestation to eliminate the likelihood of secondary implantation. (4) In contrast to the rarity of a primary abdominal pregnancy, secondary forms occur more frequently, usually as a result of tubal abortion or rupture, with reimplantation of the conceptus on a proximate peritoneal surface. A newer schematic categorizes the condition based upon gestational age or by location of implantation. An abdominal pregnancy less than 20 weeks of gestation is considered early. The uterine surface is most often the site of implantation, but the liver, spleen, lesser sac, and undersurface of the diaphragm serve as additional sites of permeation. An advanced abdominal pregnancy is one which has persisted past 20 weeks; implantation generally occurs in the pouch of Douglas, or on the proximate bowel and omentum.

Diagnosis of abdominal pregnancy is quite difficult and is often delayed due to the rarity of the condition and the protean presentations. General malaise, nausea and vomiting, vaginal bleeding, decreased fetal movement, or fetal movement high in the abdomen may be noted. Serologic evaluation has not proven definitive as maternal serum concentrations of human chorionic gonadotropin, human placental lactogen, progesterone, estriol, estradiol, as well as maternal serum alpha fetoprotein (MSAFP) may not differ from that of a normal pregnancy.

No specific technologic modality exists for diagnosing abdominal pregnancy. Radiography and hysterography were the prior gold standards. While there was great hope that ultrasound would prove to be the ultimate panacea for diagnosis, the accuracy has been imperfect and apt to be misleading. Sonographic assessments optimal for diagnosis are enhanced if the technician and interpreter of images are familiar with acoustic patterns associated with an extrauterine pregnancy. Extended field of view (EFOV) sonography has been recently utilized as a diagnostic modality for abdominal pregnancy. EFOV sonography allows measurements of sizable structures and delineates anatomic details which cannot be displayed with conventional sonography. This technique creates high-quality panoramic images without impedances to resolution due to higher frequency transducers, color and power Doppler functions, harmonic imaging and 3-dimensional technology. (5) Unfortunately, few medical centers are knowledgeable of, nor have the capability to utilize, this technique. CT scans and MRI have in addition been used successfully to complement sonography in providing a preoperative diagnosis. While MRI is currently considered the gold standard for diagnosis, as technology improves, it is likely that this too shall become obsolete.

No definitive consensus exists as to how to provide care to patients with abdominal pregnancy, or when to intervene; each case should be individualized. Some studies state that if the fetus is less than 24 weeks gestation, early operative intervention is advised to avoid massive maternal hemorrhage. Other studies conclude that if the pregnancy is over 24 weeks, has normal anatomy/amniotic fluid, the pregnancy should be allowed to progress with intensive hospital surveillance.

No single surgical technique exists for removing an abdominal pregnancy. While exploratory laparotomy has been touted as the management gold standard, whether the abdominal pregnancy is early or advanced, recent case reports in the literature promote laparoscopic treatment for early abdominal pregnancies. Placental management following delivery remains controversial. Various studies postulate that if the complete blood supply to the placenta can be easily approached and controlled, then its complete removal is recommended. However, other surveys recommend if the placenta is implanted on posterior peritoneal surfaces, mesentery, vascular immobile surfaces or unremovable surfaces such as the bladder, then placental conservation is advised. While methotrexate has been utilized in the past to effect rapid placental degeneration, the accumulation of necrotic tissue increases the risk for infection and, therefore, even its use as a therapeutic modality should be approached with caution.

Despite the advances in medicine, management of abdominal pregnancy still remains an obstetrical enigma. Perhaps within the next 130 years, a definitive etiology, diagnostic and treatment modality will be elucidated. In the interim, a high index of suspicion, case individualization, and a multidisciplinary approach will be required to affect a positive outcome.

References

1. Cotter A, Izquierdo L, Heredia F. Abdominal pregnancy. Available at: http://www.thefetus.net.

2. Atrash HK Friede A, Hogue CJ. Abdominal pregnancy in the United States: frequency and maternal mortality. Obstet Gynecol 1987;69:333-337.

3. Ramachandran K, Kirk P. Massive hemorrhage in a previously undiagnosed abdominal pregnancy presenting for elective Cesarean delivery. Can J Anesth 2004;51:57-61.

4. Studdiford WE. Primary peritoneal pregnancy. Am J Obstet Gynecol 1942;44:487.

5. Cotter AM, Jacques EG, Izquierdo LA. Extended field of view sonography: a useful tool in the diagnosis and management of abdominal pregnancy. J Clin Ultrasound 2004;32:207-210.

Kecia Gaither, MD, MPH, FACOG

From the Division of Maternal Fetal Medicine, Brookdale University Hospital and Medical Center, Brooklyn, New York.

Reprint requests to Kecia Gaither, MD, MPH, FACOG, Director, Division of Maternal Fetal Medicine, Brookdale University Hospital and Medical Center, 1 Brookdale Plaza, Snapper Room 101, Brooklyn, NY 11212. Email: kgaither@brookdale.edu
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Title Annotation:Editorial
Author:Gaither, Kecia
Publication:Southern Medical Journal
Date:Apr 1, 2007
Words:993
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