Zachary S. Bowman

Accuracy of ultrasound for the prediction of placenta accreta

OBJECTIVE Ultrasound has been reported to be greater than 90% sensitive for the diagnosis of accreta. Prior studies may be subject to bias because of single expert observers, suspicion for accreta, and knowledge of risk factors. We aimed to assess the accuracy of ultrasound for the prediction of accreta. STUDY DESIGN Patients with accreta at a single academic center were matched to patients with placenta previa, but no accreta, by year of delivery. Ultrasound studies with views of the placenta were collected, deidentified, blinded to clinical history, and placed in random sequence. Six investigators prospectively interpreted each study for the presence of accreta and findings reported to be associated with its diagnosis. Sensitivity, specificity, positive predictive, negative predictive value, and accuracy were calculated. Characteristics of accurate findings were compared using univariate and multivariate analyses. RESULTS Six investigators examined 229 ultrasound studies from 55 patients with accreta and 56 controls for 1374 independent observations. 1205/1374 (87.7% overall, 90% controls, 84.9% cases) studies were given a diagnosis. There were 371 (27.0%) true positives; 81 (5.9%) false positives; 533 (38.8%) true negatives, 220 (16.0%) false negatives, and 169 (12.3%) with uncertain diagnosis. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 53.5%, 88.0%, 82.1%, 64.8%, and 64.8%, respectively. In multivariate analysis, true positives were more likely to have placental lacunae (odds ratio [OR], 1.5; 95% confidence interval [CI], 1.4-1.6), loss of retroplacental clear space (OR, 2.4; 95% CI, 1.1-4.9), or abnormalities on color Doppler (OR, 2.1; 95% CI, 1.8-2.4). CONCLUSION Ultrasound for the prediction of placenta accreta may not be as sensitive as previously described.

Risk Factors for Placenta Accreta: A Large Prospective Cohort

OBJECTIVE Placenta previa and prior cesarean delivery are known risk factors for placenta accreta. However, other risk factors have not been identified. Our objective was to examine risk factors for accreta using data collected prospectively in a large multicenter cohort. STUDY DESIGN Secondary analysis of women with accreta compared to those without accreta in a large multicenter cesarean delivery cohort. Potential accreta risk factors were examined by univariate and multivariate analyses. RESULTS In this study, 196 of 73,257 (0.27%) cesarean deliveries were complicated by accreta. As expected, women with increasing numbers of prior cesareans were more likely to have an accreta (p < 0.001), as were women with previa (adjusted odds ratio [OR], 34.9; 95% confidence interval [CI], 22.4-54.3). We also considered only patients with previa and examined the following variables: maternal demographics, prior cesareans, interval between deliveries, parity, body mass index, tobacco use, and coexisting hypertension or diabetes. In this model, patients with previa and two or three prior cesarean deliveries had an adjusted OR for accreta of 4.9 (95% CI, 1.7-14.3) or 7.7 (95% CI, 2.4-24.9), respectively. However, no other variables were significantly associated with accreta. CONCLUSION Patients with previa have increased risk for accreta that increases with the number of prior cesarean deliveries. However, no other maternal characteristics were associated with accreta.

Risk factors for unscheduled delivery in patients with placenta accreta

OBJECTIVE Patients with suspected placenta accreta have improved outcomes with scheduled delivery. Our objective was to identify risk factors for unscheduled delivery in patients with suspected placenta accreta. STUDY DESIGN This was a cohort study of women with antenatally suspected placenta accreta. Women who delivered prior to a planned delivery date were compared with women who had a scheduled delivery. Data were analyzed using a Student t test, χ(2), logistic regression, and survival analyses. Variables included in the analyses were episodes of antenatal vaginal bleeding, preterm premature rupture of membranes (PPROM), uterine contractions, prior cesarean deliveries, interpregnancy interval, parity, and patient demographic factors. A value of P < .05 was considered significant. RESULTS Seventy-seven women with antenatal suspicion for placenta accreta were identified. Thirty-eight (49.4%) had an unscheduled delivery. Demographics were similar between groups. Unscheduled patients delivered earlier (mean 32.3 vs 35.7 weeks, P < .001) and were significantly more likely to have had vaginal bleeding (86.8% vs 35.9%, P < .001) and uterine activity (47.4% vs 2.6%, P < .001). Each episode of antenatal vaginal bleeding was associated with an increased risk of unscheduled delivery (adjusted odds ratio, 3.8; 95% confidence interval, 1.8-7.8). Risk of earlier delivery was even greater when associated with PPROM (P < .001). CONCLUSION Among women with suspected placenta accreta, those with antenatal vaginal bleeding were more likely to require unscheduled delivery. This risk increases further in the setting of PPROM and/or uterine contractions. These clinical factors should be considered when determining the optimal delivery gestational age for women with placental accreta.

Interobserver Variability of Sonography for Prediction of Placenta Accreta

The sensitivity of sonography to predict accreta has been reported as higher than 90%. However, most studies are from single expert investigators. Our objective was to analyze interobserver variability of sonography for prediction of placenta accreta.

Sonographic appearance of the placenta.

The placenta forms the interface between the mother and the fetus and is essential to fetal growth and development. In addition to the exchange of gases and nutrients, it serves immunologic and endocrine functions that protect the fetus and support physiological changes in pregnancy. Although often largely ignored during routine obstetric ultrasound and discarded after delivery, careful sonographic evaluation of the placenta can identify abnormalities that have profound implications for pregnancy outcomes and management. After describing the normal sonographic appearance of the placenta and normal anatomical variations, we review pathologic placental conditions, emphasize ultrasound findings, and highlight implications for pregnancy management and outcomes.

Cesarean Delivery and Risk for Subsequent Ectopic Pregnancy

OBJECTIVE This study aims to examine the risk for subsequent ectopic pregnancy in women with prior cesarean delivery. STUDY DESIGN Women with a history of at least one cesarean delivery in the state of Utah during 1996 to 2011 were identified and compared with women with vaginal delivery only. The primary outcome was subsequent ectopic pregnancy. Data were analyzed by multivariate logistic regression and stratified by first, second, or third live births. Model covariates included maternal age, ethnicity, marital status, education level, gravidity, and prior ectopic pregnancy. RESULTS Overall, 260,249 women with at least one live birth were identified. After exclusions, 255,082, 154,930, and 70,228 women had at least one, two, and three prior live births that lead to 531, 199, and 62 subsequent ectopic pregnancies, respectively. Women who had one prior cesarean delivery were not at increased risk for subsequent ectopic pregnancy in relation to women with no prior cesarean delivery. However, women with two of two, two of three, or three of three prior cesareans had increased risk for subsequent ectopic pregnancy with odds ratios (95% confidence interval) of 1.54 (1.06-2.22), 3.50 (1.49-8.24), and 1.99 (1.00-3.98), respectively. CONCLUSION History of two or three cesarean deliveries is associated with increased risk for subsequent ectopic pregnancy.

Velamentous Cord Insertion With Variable Umbilical Cord Doppler Changes

The umbilical cord usually inserts centrally into the placental disk. In approximately 1% to 2% of singleton pregnancies, velamentous cord insertion occurs, with insertion of the cord into the membranes beyond the margin of the placenta. Velamentous cord insertion is associated with risks of preterm birth, cesarean delivery, low birth weight, low Apgar scores, transfer to the neonatal intensive care unit, and perinatal death.1 We present a case of early-onset fetal growth restriction with intermittent abnormal umbilical cord Doppler findings in a patient who was subsequently discovered to have velamentous cord insertion. A 31-year-old woman, gravida 3, para 2, presented for her first sonographic examination at 18 weeks’ gestation by her last menstrual period, at which time the fetus measured 11 days behind. Follow-up at 22 weeks by the last menstrual period revealed a worsening lag of 3 weeks and oligohydramnios. The workup included amniocentesis for karyotype and assessment of viral infection. The karyotype returned as 46,XX, and the infectious workup results were negative. The patient elected for expectant management with serial sonographic examinations for growth, serial Doppler examinations of umbilical artery waveforms, and antenatal testing in the third trimester. By 30 weeks’ gestation, the fetus measured 4 weeks behind, and umbilical artery Doppler assessment revealed elevated systolic-to-diastolic (S/D) ratios (4.79–5.97) as well as pulsatile flow in the umbilical vein (Figure 1A). Close follow-up was recommended. A follow up Doppler examination 1 week later showed normal S/D ratios (1.9– 2.9; Figure 1B).2 At that time, the placental cord insertion was noted to be velamentous (Figure 1, C–E). Although the fetal size remained less than the 5th percentile for gestational age, there was adequate interval growth, normal subsequent umbilical cord Doppler findings, and an otherwise reassuring fetal status for the remainder of the pregnancy. An elective repeat cesarean delivery was performed at 37 weeks’ gestation, and the patient delivered a female neonate weighing 1815 g with normal cord blood gases and Apgar scores of 7 and 8 at 1 and 5 minutes, respectively. On manual removal of the placenta, a velamentous umbilical cord insertion was confirmed (Figure 1F). The neonate was initially hospitalized for feeding difficulties and low birth weight but was discharged in stable condition on day 19 of life with no evidence of infection or genetic or anatomic malformations. Placental pathologic findings were notable for the velamentous cord, placental weight less than the 10th percentile, and an intervillous thrombus of less than 1% of the placental volume. In the absence of abnormal genetic, anatomic, or infectious abnormalities, the fetal growth restriction and intermittent abnormal Doppler findings were attributed to the velamentous cord. Velamentous cord insertion occurs in 1.5% of singleton gestations, and the 2013 American Institute of Ultrasound in Medicine practice guideline for the performance of obstetric ultrasound examinations recommend that “the placental cord insertion site should be documented when technically possible.”3 Fetal growth restriction (eg, estimated fetal weight <10th percentile) is known to be associated with abnormal umbilical artery Doppler findings. Poor placentation or hypoxemia can present with elevated S/D ratios, absent or reversed enddiastolic flow in the umbilical arteries, and pulsations of the umbilical vein. Absent or reversed end-diastolic flow may precipitate delivery, as reversed end-diastolic flow is considered an unstable clinical state that may precede fetal death by hours to days. Doppler changes in growth-restricted fetuses are reflective of a deteriorating circulatory status and are thought to be progressive. Umbilical vein pulsations are usually considered very late signs of fetal asphyxia and impending cardiac failure.4,5 In our patient, the findings of elevated umbilical artery S/D ratios with diastolic flow and umbilical vein pulsations were atypical and in the setting of fetal growth restriction led to increased surveillance (and patient anxiety). We considered velamentous cord insertion as a cause of both fetal growth restriction and intermittent abnormal cord Doppler findings. Unrelated to fetal growth restriction and hemodynamic compromise, pulsations of the umbilical vein have also been associated with umbilical cord restriction.5 Skulstad and colleagues5 proposed “a congestion in the umbilical vein . . . stretches the wall, or a