Which of the following statements is true of heterotopic pregnancies?
A. They have a lower mortality rate than ectopic pregnancies.
B. They have similar risk factors to those of ectopic pregnancies.
C. They occur more commonly in natural cycles than with assisted reproductive treatment.
D. They present with acute rupture very infrequently.
Heterotopic pregnancy (HP) is the coexistence of an intrauterine and an extrauterine pregnancy. The majority of cases of HP are thought to arise from multiple ovulations. Although its incidence was once considered rare (1/30,000 pregnancies), the incidence has increased significantly since the advent of assisted reproductive technology (ART). The true incidence of HP is unknown but has been estimated to be as high as 1.5% in women treated with ART, which is 100 times higher than HP that occurs with natural cycles.
Risk factors for HP are similar to those for ectopic pregnancy and include pre-existing tubal disease, pelvic inflammatory disease, prior ectopic pregnancy, prior tubal surgery, use of intrauterine devices, and ART. Patient presentations vary, and some may even be asymptomatic. Presenting signs and symptoms include lower abdominal pain (30-80%), vaginal bleeding (approximately 30%) and adnexal mass (43%), enlarged uterus, and hemorrhagic shock. Approximately 50% of heterotopic pregnancies present with acute rupture.
Heterotopic pregnancy presents a major diagnostic challenge for the emergency physician as well as the obstetrician. It is common to think that an intrauterine pregnancy on ultrasound rules out an ectopic pregnancy. However, an HP still may exist and, if left undiagnosed or if the diagnosis is delayed, there may be dire maternal consequences. Soriano et al. found that patients with HP were more likely to have hemodynamic instability, to have more free fluid in the pelvis, and to require more blood transfusions than patients with ectopic pregnancy.
Early diagnosis of HP is essential. The majority of heterotopic pregnancies are diagnosed between 5 and 8 weeks (70%), while 20% are diagnosed between 9 and 10 weeks, and the remaining 10% after 11 weeks. The serum beta-hCG levels are not helpful because they are usually high and may in fact appropriately increase in serial examinations.
Because 95% of heterotopic pregnancies are located either in the fallopian tubes or the ovaries, transvaginal ultrasound is superior to transabdominal ultrasound in making the diagnosis of HP. It is important to keep HP in the differential diagnosis for those pregnant patients who present with shock or continue to complain of severe abdominal pain with or without vaginal bleeding. It is crucial that the adnexal structures be visualized. Consider HP if there is an IUP but the adnexa are poorly visualized or abnormal and there is free fluid in the pelvis.
Treatment of the ectopic pregnancy depends on the patient's clinical presentation. The literature states that laparoscopy for salpingectomy or salpingotomy is the standard treatment for these patients. In stable patients, the use of potassium chloride, methotrexate, RU486, or prostaglandins is useful in the treatment of the ectopic pregnancy but raises concern for possible compromise of the intrauterine gestation.
The survival rate for the intrauterine pregnancy has been documented to be approximately 66% in patients who undergo laparoscopic surgery to remove the ectopic pregnancy. Maternal hypovolemia due to hemorrhagic shock increases the likelihood of demise of the intrauterine pregnancy. The maternal mortality rate for HP has been cited as being just under 1% as compared to ectopic pregnancy, which carries a mortality rate of 0.3/1000. This larger mortality rate likely is due to delays in diagnosis.
Answer: B
