History and physical examination to estimate the risk of ectopic pregnancy: validation of a clinical prediction model.

STUDY OBJECTIVE: To prospectively validate a clinical prediction model for ectopic pregnancy (EP). METHODS: Prospective cohort with 14-month derivation and 12-month validation phases. All hemodynamically stable, first-trimester patients with abdominal pain or vaginal bleeding who presented to a military teaching hospital emergency department underwent follow-up until an outcome of intrauterine pregnancy (IUP) or EP was established. Patients were separated into the high-risk group, defined as having either peritoneal signs or definite cervical motion tenderness; intermediate-risk group, defined as the presence of pain or tenderness, other than midline cramping, plus absence of fetal heart tones, and absence of tissue visible at the cervical os; and low-risk group (neither high- nor intermediate-risk) using recursive partitioning. RESULTS: Summarizing both phases, 915 patients had 845 (93%) IUPs and 70 (7.6%) EPs, with 18 (1.9%) lost to follow-up. The clinical prediction model classified 75 (8.2%) into the high-risk group (sensitivity 31%, 95% confidence interval [CI] 21% to 44%; specificity 94%, 95% CI 92% to 95%); and 644 (70%) in the intermediate-risk group (sensitivity 98%, 95% CI 89% to 100%; specificity 25%, 95% CI 22% to 29%). The remaining 196 (21%) patients who met neither high-risk nor intermediate-risk criteria were classified into the low-risk group. On the basis of EP prevalence of 7.7%, the risk of EP was less than 1% (95% CI 0% to 3%) for the low-risk group, 7% (95% CI 5% to 10%) for the intermediate-risk group, and 29% (95% CI 19% to 41%) for the high-risk group. CONCLUSION: This clinical prediction model is useful for estimating the risk of EP in first-trimester patients, particularly when ancillary testing is equivocal or not readily available.

Low amniotic fluid volume is poorly identified in singleton and twin pregnancies using the 2 x 2 cm pocket technique of the biophysical profile.

BACKGROUND: This study was done to determine the accuracy of the 2 x 2 cm pocket identifying low amniotic fluid (AF) volume in singleton and twin pregnancies. METHODS: The AF volume was evaluated by ultrasonography for the presence of a 2 x 2 cm pocket before amniocentesis. The actual AF volume was then determined by a diazo-dye reaction with subsequent spectrophotometric analysis using paraminohippurate. RESULTS: The AF volume was low in 21 of the 79 singleton pregnancies and normal in 47; hydramnios was present in 11. Among amniotic sacs of the 60 twin pairs, oligohydramnios was found in 33 amniotic sacs. normal AF volume in 80 sacs, and high volume in 7. An AF pocket smaller than 2 x 2 cm was identified in only 3 of the 79 singleton pregnancies and in only 2 of the 120 twin amniotic sacs. CONCLUSIONS: Judging AF volume on the basis of a 2 x 2 cm pocket misses more than 90% of cases of oligohydramnios in singletons and twins.

Risk factors for secondary arrest of labor among women >41 weeks' gestation with an unfavorable cervix undergoing membrane sweeping for cervical ripening.

OBJECTIVE: To identify the risk factor(s) for secondary arrest of labor among women with an unfavorable cervix at > 41 weeks' gestation. METHODS: Prospectively all gravid women with a Bishop score of < or = 4 and no contraindication to a vaginal delivery were candidates for this study. Univariate analysis followed by logistic regression modeling were used to identify variables with a significant association. RESULTS: Over a 9-month period, 115 women entered into the study. In univariate analysis, variables with a significant association with cesarean delivery: (1) non-Caucasian race (P = 0.007), Bishop score < 7 at hospitalization; P = 0.001, and reason for admission (P = 0.017). Logistic regression analysis yielded OR 4.7 (1.6, 15) non-Caucasian race and 9.5 (3.2, 30.8) Bishop < 7 on admission. CONCLUSION: Pregnancies > 41 weeks with an unfavorable cervix, non-Caucasian race and a failure to achieve a Bishop score of > or = 7 prior to hospitalization were significant risk factors for abdominal delivery.

Derivation of a clinical prediction model for the emergency department diagnosis of ectopic pregnancy.

OBJECTIVE: To derive a clinical prediction model for estimating the pretest probability of ectopic pregnancy in ED patients with first-trimester abdominal pain or vaginal bleeding. METHODS: All hemodynamically stable first-trimester patients presenting to the ED of a tertiary care military teaching hospital over a 14-month period with a chief complaint of abdominal pain and/or vaginal bleeding had clinical data coded prior to determining outcome. They were then followed longitudinally until a criterion standard pregnancy outcome was established. RESULTS: Of the 486 patients enrolled, 280 (58%) had viable intrauterine pregnancies, 167 (34%) had nonviable intrauterine pregnancies, and 39 (8%) had ectopic pregnancies. Using a recursive partitioning model, a high-risk group was derived (that was separated from intermediate and low-risk groups), consisting of patients with abdominal peritoneal signs or definite cervical motion tenderness, with a sensitivity of 31% (95% CI: 17-48%), a specificity of 93% (95% CI: 90-95%), a positive likelihood ratio of 4.3, and a negative likelihood ratio of 0.74. A low-risk group, consisting of patients with either fetal heart tones or tissue at the cervical os, or the absence of pain other than midline menstrual-like cramping and lacking any pelvic tenderness, was differentiated from an intermediate-risk group, with a sensitivity of 96% (95% CI: 81-100%), a specificity of 22% (95% CI: 18-26%), a positive likelihood ratio of 1.2, and a negative likelihood ratio of 0.17. CONCLUSION: A clinical prediction model for estimating the probability of ectopic pregnancy in ED patients has been derived. It may prove to have practical clinical application for estimating pretest probability of ectopic pregnancy as well as assisting in medical decision making when laboratory and ultrasonographic findings are nondiagnostic. Clinical application should await prospective validation in an independent sample.

Do multiple measurements employing different ultrasonic techniques improve the accuracy of amniotic fluid volume assessment?

This investigation was undertaken to determine if the accuracy of the ultrasound assessment of abnormal amniotic fluid volume (oligohydramnios or polyhydramnios) is improved by employing multiple sonographic amniotic fluid measurements. Four ultrasound techniques consisting of the subjective assessment (ultrasonic visualization without measurement), largest vertical pocket, amniotic fluid index and 2-diameter pocket technique were performed followed by amniocentesis and dye-dilution confirmation of amniotic fluid volume in 66 singleton pregnancies. The ultrasound accuracy to detect abnormal amniotic fluid volume ranged from 61% with the largest vertical pocket to 70% with the 2-diameter pocket procedure used separately. Receiver operator characteristic curves demonstrated that combining the 4 ultrasonic measurements did not improve the accuracy of identifying amniotic fluid volumes.

The accuracy of the summated amniotic fluid index in evaluating amniotic fluid volume in twin pregnancies.

OBJECTIVE: Our purpose was to determine the accuracy of the summated amniotic fluid index designed to estimate the total amniotic fluid volume in twin pregnancies. STUDY DESIGN: The summated amniotic fluid index was measured in 62 normal diamniotic twin pregnancies by adding the deepest vertical pockets in the four quadrants. Actual amniotic fluid volume was then determined in all 124 amniotic sacs by amniocentesis and a dye-dilution technique. For data analysis, amniotic fluid volumes were classified by percentile with use of previously reported norms. RESULTS: There were significant differences in the percentile distribution of amniotic fluid volume as estimated by the summated amniotic fluid index and the actual volume as determined by dye dilution (p < 0.001). The summated amniotic fluid index has a sensitivity of only 13% in predicting amniotic sac volume. CONCLUSION: The summated amniotic fluid index is a poor predictor of intertwin differences in amniotic fluid volume and cannot identify twin pairs at risk for oligohydramnios and hydramnios.

Accuracy of ultrasonography in evaluating amniotic fluid volume at less than 24 weeks' gestation.

The purpose of this investigation was to evaluate the accuracy of common sonographic techniques in assessing the amniotic fluid volume in pregnancies of less than 24 weeks' gestation. Patients at less than 24 weeks' gestation undergoing an amniocentesis for the placement of prostaglandin F2 alpha for termination (because of genetic or fetal anomalies, or both) were assessed for amniotic fluid volume. All fetuses were alive at the time of prostaglandin instillation. The amniotic fluid index and two-diameter pocket were used to determine the amniotic fluid volume. Prior to the prostaglandin instillation, the amniotic fluid volume was determined with para-aminohippurate using a diazo dye reaction with spectrophotometric analysis. The amniotic fluid volume was determined in 21 pregnancies between 15 and 24 weeks' gestation, yielding volumes ranging from 189 to 1840 ml. Using published standards for amniotic fluid volume in singleton pregnancies, oligohydramnios was present in three gestations, the volume was found to be normal in 15, and hydramnios complicated three pregnancies. The two-diameter pocket identified the amniotic fluid volumes correctly more often (18 of 21 [85.7%]) than the amniotic fluid index (10 of 21 [47.6%]) (P = 0.02). Normal amniotic fluid volume was identified in nine of 15 (60%) pregnancies by the amniotic fluid index and in 14 of 15 (93.3%) by the two-diameter pocket (P = not significant). Abnormal amniotic fluid volumes, oligohydramnios, and hydramnios were recognized more often by the two-diameter pocket (66.7%) than by the amniotic fluid index (1 of 6 [16.7%], P = not significant).