Consider medical management only when no active uterine bleeding is present.
Some established biochemical markers have been applied in novel ways in diagnosing placenta accreta. For example, Zelop et al retrospectively reviewed the cases of 11 women who had undergone cesarean hysterectomy for placenta previa with accreta and compared them to 14 women with placenta previa alone. In 5 of 11 cases, women with accreta had alpha-fetoprotein (AFP) levels greater than 2 multiples of the median (MOM), compared to none in the previa-only group.12 This suggests that abnormal placental attachment results in myometrial invasion with increased diffusion of fetal AFP into the maternal circulation.
Hung and colleagues reviewed over 9,000 deliveries in the Taiwan Down Syndrome Screening Group.13 After other causes of elevated maternal AFP were excluded, regression analysis showed a relative risk of 8.3 for the presence of accreta when AFP levels exceeded 2.5 MOM in the second trimester. Ophir et al reported 2 cases of women with elevated creatine kinase levels as early as 22 weeks’ gestation who subsequently were diagnosed with placenta accreta.14 The investigators theorized that trophoblastic invasion of the myometrium results in muscular damage and elevated serum creatine kinase levels. While more studies are needed, serum markers may exist for the presence of accreta, providing another asset for earlier diagnosis and preparation.
TABLE 2
Ultrasound criteria for diagnosis of placenta accreta
| Thinning of the hypoechoic retroplacental myometrium to <2 mm |
| Absence of the hypoechoic myometrium in the lower uterine segment between placenta and bladder |
| Disruption of the hyperechoic uterine serosa-to-bladder interface |
| Extension of the placenta beyond the myometrial boundary |
| Lacunar flow and venous lakes within the placenta |
Medical management
In recent years, reports of select patients undergoing medical management for placenta accreta have begun to appear. Although the number of these patients has been small, with some women ultimately requiring surgical intervention, the vast majority have done well. Even so, medical management should be considered only when the patient wishes to preserve her fertility and when no active uterine bleeding is present. Adequate discussion of the potential risks and benefits also is crucial.
Methotrexate (MTX) is the cornerstone of medical management, although case reports also have described the use of antibiotics, uterotonics, surveillance with ultrasound, and the monitoring of human chorionic gonadotropin (hCG) levels. There is no agreed-upon regimen for the use of MTX or adjunctive therapies such as antibiotics and oxytocin. However, after reviewing the relevant literature, we can suggest some general guidelines.
At the time of delivery, the cord and membranes should be ligated as high as possible. Broad-spectrum antibiotics, for prophylaxis, and oxytocin should be administered during the initial 72 hours. In addition, ultrasound should be performed daily to monitor involution and placental vascularity, which should decrease over time.
If hCG levels plateau, placental vascularity persists, or placental involution stalls after this initial 72-hour period, MTX should be administered (1 mg/kg) on alternate days for a total of 4 to 6 doses. Medical management should be stopped if liver function tests are 2 or more times the normal value or there is evidence of thrombocytopenia (platelet levels below 100,000), neutropenia (white blood cell count below 2,000), or renal dysfunction (creatinine levels greater than 1.5 mg/dL). If the patient becomes clinically unstable or placental tissue fails to resolve following MTX therapy, hysterectomy should be considered.
Expectant management is another valid approach in select cases (TABLE 3). It is more likely to be successful when vascularity is no longer present on ultrasound examination of the placenta. Panoskaltsis and colleagues reported 2 cases of expectant management.15 In 1 case, the placental mass and vascularity regressed spontaneously with time following vaginal delivery, and normal menses resumed at 9 months postpartum. In the second case, MTX was given when the placental mass maintained vascularity on ultrasound exam at postpartum day 12. Ultimately, this mass involuted to a 5-cm mass without vascularity at 1 year. Normal menses resumed, and hCG levels returned to zero. Follow-up in these patients has been short. Fertility has yet to be documented in either patient, although the resumption of menses is an encouraging sign.
When it is successful, medical management has many potential benefits. A woman retains her future fertility and avoids the morbidity and mortality of gravid hysterectomy. Even with antenatal diagnosis of placenta accreta, gravid hysterectomy can result in high-volume blood loss and coagulopathy due to the difficult nature of the procedure.5 Proponents of medical management would further argue that there are few disadvantages to attempting medical management in clinically stable patients, provided follow-up is close. Even when a placental mass fails to resolve or vascularity or vaginal bleeding occurs, an interval of even a few days after delivery may simplify hysterectomy due to uterine involution and a concurrent decrease in vascularity.