Detection of group B streptococcus: comparison of an optical immunoassay with direct plating and broth-enhanced culture methods.

The aim of this study was to compare the diagnostic accuracy of an optical immunoassay (STREP B OIA, Biostar) to direct plating and broth-enhanced culture for the detection of group B streptococcus (GBS) colonization of the lower genital tract in pregnant women. GBS cultures from the lower genital tract were obtained in a prospective fashion using a dual swab transport system from patients with risk factors for perinatal GBS infection. One swab was used to inoculate a trypticase soy agar plate with 5% sheep blood (TSA) and then placed in Lim broth. The other swab was used to perform the Strep B OIA. Growth of GBS by either direct plating or broth-enhanced culture was used as the gold standard for determining GBS colonization. Of the 524 women in the study, 90 women had positive cultures (either TSA or Lim broth). The sensitivity, specificity, positive predictive value, and negative predictive value of the Strep B OIA were 47% (42/90), 96% (416/434), 70% (42/60), 90% (416/464). The sensitivity, specificity, positive predictive value, and negative predictive value of the TSA were 61% (55/90), 100% (434/434), 100% (55/55), 93% (434/469). The sensitivity, specificity, positive predictive value, and negative predictive value of Lim broth were 97% (87/90), 100% (434/434), 100% (87/87), and 97% (434/437). The sensitivity of the Strep B OIA to detect light GBS colonization and heavy GBS colonization, as determined by the TSA, was 53% (19/36) and 90% (17/19), respectively. The Strep B OIA and direct agar plate culture appear to be of limited clinical value due to their poor sensitivities. This study also demonstrates the need to use a selective medium such as Lim broth when assessing for GBS colonization of the lower genital tract.

Chorioamnionitis does not affect fetal urine production in patients with premature rupture of membranes.

The objective of this study was to evaluate fetal urine production rate in patients with premature rupture of membranes in the presence or absence of chorioamnionitis and to determine its clinical usefulness. Fetal urine production was evaluated in 30 women between 24 and 39 weeks' gestational age with ruptured membranes. Fetal bladder measurements were determined every 3-5 min for 30-90 min. Chorioamnionitis was defined by both clinical criteria and histological examination of the placenta. The last determination of fetal urine production rate prior to delivery was compared in patients with and without histologic and/or clinical chorioamnionitis. Fetal urine production rate was corrected for gestational age using birth weight prior to analysis. A total of 96 assessments of fetal urine production were performed (range 1-16 per patient). Twelve subjects (40%) had no evidence of chorioamnionitis (group 1), 10 (33%) had histologic chorioamnionitis alone (group 2), and eight (27%) had both clinical and histologic chorioamnionitis (group 3). The mean (+/- SD) urine production rates in these groups were 9.43 +/- 3.15 ml/kg/hr, 10.65 +/- 3.43 ml/kg/hr, and 9.97 +/- 2.81 ml/kg/hr, respectively. The difference in fetal urine production rate between the three groups was not statistically significant. A power analysis revealed that individual group sizes were adequate to document a 50% increase in fetal urine production rate with a type II error of < 10%. There were no documented cases of fetal infection based on neonatal cultures. The presence of histologic or clinical chorioamnionitis does not significantly affect fetal urine production in patients with premature rupture of membranes. The prospective assessment of fetal urine production rate does not appear to be clinically useful as an early indicator of chorioamnionitis.

Early gestational glucose screening and gestational diabetes.

OBJECTIVE: The purpose of this study was to determine the benefit of early glucose screening prior to 24 weeks' gestation in detecting gestational diabetes. STUDY DESIGN: A retrospective analysis of 329 patients who received both early and complete prenatal care at the University of Illinois was performed. A 50-g, 1-hour glucose screen was performed at the first prenatal visit. An abnormal glucose screen, defined as blood sugar > 135 mg/dL, was followed by a 100-g, 3-hour glucose tolerance test. Gestational diabetes was defined as the presence of two or more abnormal values on the three-hour test. This protocol was repeated again at 28 weeks in all patients except those diagnosed as diabetic by having abnormal early three-hour tests. Data collected included maternal age, race, gravidity, presence of risk factors, pregnancy weight gain at glucose testing and delivery, neonatal birth weight and trauma. Data were analyzed using analysis of variance and chi 2 testing, with P < .05 considered significant. RESULTS: Gestational diabetes was diagnosed in 20 (6.1%) of the study patients. Eight (40%) of the gestational diabetics in the study population were detected with the early screening protocol. Factors associated with early detection of glucose intolerance included maternal age > 30 years (P < .001), black race (P < .001) and the presence of risk factors (P < .0001). Poor pregnancy weight gain was associated with the late development of glucose intolerance (P < .001). Gestational diabetes was subsequently diagnosed in 16% (6/38) of those patients who had, on early testing, an elevated one-hour glucose screen and negative three-hour glucose tolerance test when testing was repeated in the third trimester. CONCLUSION: Early gestational glucose screening may be beneficial in detecting gestational diabetes in patients over 30 years old who are black or who have risk factors for diabetes. Consideration should be given to repeat glucose testing in the early third trimester in patients with false positive early one-hour screening tests.

Catalase activity as a predictor of amniotic fluid culture results in preterm labor or premature rupture of membranes.

OBJECTIVE: To evaluate catalase activity as a rapid predictor of microbial invasion of amniotic fluid (AF). METHODS: The study population consisted of 74 patients before 36 weeks' gestation with preterm labor or premature rupture of membranes (PROM). Subjects were excluded if there was evidence of clinical chorioamnionitis or fetal distress at admission. Amniocentesis was done within 24 hours of admission, and the AF was cultured for aerobic and anaerobic bacteria and for Mycoplasma species. All AF samples were Gram stained, and slides were examined by microbiology technologists. Amniotic fluid catalase activity was measured immediately after amniocentesis using a commercially available kit. The sensitivity of the Gram stain and catalase activity were compared using McNemar exact test. RESULTS: Amniotic fluid cultures were positive in 12 of 37 (32%) patients presenting with preterm labor and in 21 of 37 (56%) patients with PROM. Catalase activity was significantly more sensitive than Gram stain in detecting positive AF cultures in cases of PROM (P < .001) and preterm labor (P < .04). CONCLUSION: Catalase activity is a simple, rapid test that is useful in identifying subclinical intra-amniotic infection in patients with preterm labor or PROM.

Effect of amniotic fluid volume on ultrasonic fetal weight estimation.

We evaluated the relationship between the amniotic fluid index and the accuracy of fetal weight estimation using ultrasonography. Six hundred and sixty-four patients, between 20 and 42 weeks' gestational age, who were delivered within 1 week of a sonographic examination were studied. Five formulas for estimating fetal weight also were studied. Systematic and random errors in predicting birth weight were analyzed relative to birth weight and amniotic fluid index. The accuracy of sonographic fetal weight estimation was independent of amniotic fluid index across all gestational ages and birth weights. Each of the five formulas had similar error percentages, and no significant differences were detected. Predicted fetal weight was significantly underestimated with each of the formulas studied, a finding that was also independent of birth weight and amniotic fluid index. We conclude that ultrasonography can be used reliably to estimate fetal weight in patients with altered amniotic fluid volumes.

Intrapartum fetal subcutaneous tissue/femur length ratio: an ultrasonographic clue to fetal macrosomia.

OBJECTIVE: Our purpose was to compare the accuracy of ultrasonographic intrapartum measurement of fetal abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio in predicting large-for-gestational-age fetuses. STUDY DESIGN: A cross-sectional analysis of 173 normal patients delivered of normal, appropriate-for-gestational-age infants (group 1) was performed to determine the normal changes of standard fetal biometric parameters and subcutaneous tissue throughout pregnancy. Measurements of fetal subcutaneous tissue were made at the level of the femoral diaphysis. A second group of 101 well-dated patients had these measurements obtained within 24 hours of delivery (group 2). Large for gestational age was defined as a birth weight > 90th percentile for gestational age. The sensitivity and specificity for prediction of large for gestational age of an intrapartum measurement of an abdominal circumference > 90th percentile, estimated fetal weight > 90th percentile, and fetal subcutaneous tissue/femur length ratio > 2 deviations of the mean was calculated. RESULTS: In group 1 the mean gestational age was 31.4 +/- 5.4 weeks (range 17 to 41 weeks). The femur length, abdominal circumference, and fetal subcutaneous tissue correlated well with gestational age (p < 0.0001). The fetal subcutaneous tissue/femur length ratio was stable throughout pregnancy, with a mean of 0.05 +/- 0.014 (range 0.02 to 0.09, R2 0.09). In group 2 mean gestational age was 38 +/- 2.5 weeks (range 30 to 42 weeks). Mean birth weight was 3280 +/- 740 gm (range 1513 to 4801 gm). Nineteen (19%) fetuses were large for gestational age. Significant differences were found between the appropriate- and large-for-gestational-age fetuses for birth weight, abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio (p < 0.0001). The sensitivity and specificity of the fetal abdominal circumference, estimated fetal weight, and fetal subcutaneous tissue/femur length ratio were 44% and 98%, 68% and 85%, and 82% and 96%, respectively. CONCLUSION: The fetal subcutaneous tissue/femur length ratio is a gestational age-independent parameter that has a greater sensitivity than the fetal abdominal circumference or estimated fetal weight formula for the intrapartum identification of large-for-gestational-age fetuses.

Expectant management of premature rupture of membranes with amniotic fluid cultures positive for Ureaplasma urealyticum alone.

OBJECTIVE: Our purpose was to determine maternal and neonatal outcome in patients with premature rupture of membranes and amniotic fluid cultures positive for Ureaplasma urealyticum alone. STUDY DESIGN: Amniocentesis was performed on 225 patients with premature rupture of membranes at < or = 34 completed weeks of gestation. Amniotic fluid was cultured for aerobic and anaerobic bacteria, Mycoplasma hominis, and Ureaplasma urealyticum. Patients with cultures positive for Ureaplasma urealyticum alone were managed expectantly, including erythromycin and daily biophysical profile examinations. RESULTS: Thirty-three patients (15%) had amniotic fluid cultures positive for Ureaplasma urealyticum alone, and clinical chorioamnionitis developed in three of these patients. There were no suspected or documented cases of neonatal sepsis. The incidence of infectious morbidity in patients with amniotic fluid cultures positive for Ureaplasma urealyticum alone was not significantly different from that seen in patients with negative cultures. CONCLUSION: An amniotic fluid culture positive for Ureaplasma urealyticum alone may not be an indication for a preterm delivery in patients with premature rupture of membranes.

In vitro study of amniotic fluid gram stain: effect of centrifugation.

OBJECTIVE: Gram stain of amniotic fluid (AF) is used to detect intraamniotic infection. The purpose of this study was to determine if centrifugation improved the ability of AF Gram stain to detect bacteria. METHODS: AF obtained by amniocentesis from patients with preterm labor (PTL) or preterm premature rupture of membranes (PPROM) was pooled. Individual AF samples as well as the pooled sample had a negative Gram stain for microorganisms or white blood cells (WBCs) and negative cultures. With pure bacterial cultures, a suspension equivalent to a 0.5 McFarland turbidity standard was prepared and then serially diluted in the AF to either 10(6), 10(5), 10(4), or 10(3) colony forming units (cfu)/ml. Each sample was divided into 2 equal portions, with 1 undergoing centrifugation. The Gram stains were interpreted by technologists in the clinical microbiology laboratory in a blinded fashion. Fisher's exact test was used to compare the bacterial detection rate in centrifuged vs. uncentrifuged AF samples at each concentration. RESULTS: Centrifugation of AF significantly improved the ability of the Gram stain to detect bacteria at bacterial concentrations < or =10(4) cfu/ml (P < 0.01). At concentrations > or =10(5) cfu/ml, centrifugation did not improve the ability of the Gram stain to dtect bacteria. CONCLUSIONS: At low bacterial concentrations, centrifugation of AF increases the bacterial detection rate of AF Gram stain.

Vasa previa: prenatal diagnosis with transvaginal color Doppler flow imaging.

Vasa previa carries a significant risk for fetal exsanguination and death at the time of membrane rupture. The diagnosis is rarely made before the onset of vaginal bleeding. We report the prenatal diagnosis of vasa previa with transvaginal color Doppler flow imaging in an asymptomatic patient with a succenturiate placenta.

The fetal transverse cerebellar diameter/abdominal circumference ratio: a gestational age-independent method of assessing fetal size.

The relationship between the fetal TCD and the AC throughout pregnancy was investigated in a prospective, cross-sectional study of 700 well dated, normal pregnancies between 14 and 42 weeks of gestation and tested in 30 known SGA infants. Fetal measurements included the TCD, AC, BPD, HC, and FL. The TCD/AC ratio was calculated for each patient. Statistical analysis using linear regression and Student's t-test was performed. Strong correlation existed between gestational age and transcerebellar diameter (R2 = 0.9464), between gestational age and AC (R2 = 0.9685), and between TCD and AC (R2 = 0.9561). The TCD/AC ratio was normally distributed with a mean +/- SD of 13.69 +/- 0.94% (median, 13.71%). The 10th and 90th percentiles were 12.50% and 14.86%, respectively. The ratio remained constant throughout pregnancy with respect to gestational age (R2 = 0.0084). A TCD/AC ratio greater than the 90th percentile was present in 87% (26/30) known SGA infants. The TCD/AC ratio is a stable, gestational age-independent parameter that may be useful in the early detection of fetal growth abnormalities.

Effect of time and storage temperature on amniotic fluid glucose concentration.

OBJECTIVE: To evaluate the effects of time and storage temperature on amniotic fluid (AF) glucose concentration. METHODS: Amniocentesis was performed on 47 patients with preterm labor or preterm rupture of membranes at or before 34 weeks' estimated gestation and the AF was cultured for aerobic, anaerobic, Mycoplasma, and Ureaplasma organisms. Twenty-one samples were stored at 37C, 13 were kept at room temperature (22C), and 13 were frozen (-20C). Glucose concentration was measured at 0 and 12 hours on all AF samples and at 2, 4, and 6 hours on the unfrozen samples. RESULTS: No significant change in AF glucose concentration occurred over time at any storage temperature in the 35 samples with negative cultures. In 12 AF samples with positive cultures, a significant decrease from baseline was noted at 2 and 4 hours in those kept at 37C and 22C (P = .016). Glucose concentration was unchanged in frozen samples regardless of the culture results. The initial AF glucose concentration was significantly lower in samples with positive than in those with negative cultures (P < .0001). CONCLUSION: Amniotic fluid glucose concentration does not change over 12 hours in the absence of intra-amniotic infection.

Comparison of gram stain, leukocyte esterase activity, and amniotic fluid glucose concentration in predicting amniotic fluid culture results in preterm premature rupture of membranes.

OBJECTIVE: The purpose of this study was to prospectively compare three rapid and inexpensive tests that have been proposed as predictors of amniotic fluid culture results in preterm premature rupture of membranes. STUDY DESIGN: Amniocentesis was performed on 117 patients < or = 34 weeks' gestational age with premature rupture of membranes and no clinical evidence of infection. Amniotic fluid was sent for Gram stain and aerobic, anaerobic, and Mycoplasma cultures. Leukocyte esterase activity and glucose concentration were also determined on the amniotic fluid. RESULTS: Amniotic fluid cultures were positive in 56 patients (47.8%). Leukocyte esterase activity of 1+ or 2+ and an amniotic fluid glucose concentration < or = 16 mg/dl were significantly more sensitive (p < 0.005) than Gram stain in detecting positive amniotic fluid cultures (73%, 68%, and 41%, respectively). CONCLUSIONS: Although each of these rapid tests is useful in assessing for subclinical intraamniotic infection, none of them have sufficient accuracy to make clinical decisions solely on the basis of their results.

Biophysical profile as a predictor of amniotic fluid culture results.

The biophysical profile has been proposed as a noninvasive method of detecting fetal infection in patients with preterm premature rupture of membranes (PROM). The purpose of this study was to evaluate the biophysical profile as a rapid predictor of amniotic fluid (AF) culture results in women with PROM. Amniocentesis was performed on 111 patients with PROM at or before 34 weeks' estimated gestational age. Aerobic, anaerobic, Ureaplasma, and Mycoplasma cultures were performed on the AF. A biophysical profile was performed just before the amniocentesis. Women with positive AF cultures had a significantly lower total biophysical profile score, as well as significantly lower scores for nonstress test, fetal breathing movements, fetal movements, and AF volume, than those with negative AF cultures. However, neither the total biophysical profile score nor any of the individual components had sufficient sensitivity, specificity, or positive or negative predictive value to be useful clinically in predicting culture results. Although the incidence of positive AF cultures was inversely related to the biophysical profile score, 48% of patients with a score of 8 and 27% of those with a score of 10 had positive AF cultures. The results of this study do not support use of the biophysical profile as an early predictor of AF culture results in patients with PROM.

Correlation of amniotic fluid glucose concentration and intraamniotic infection in patients with preterm labor or premature rupture of membranes.

Amniotic fluid glucose concentration has previously been suggested as a rapid and sensitive test for diagnosing intraamniotic infection. In this study, 204 patients less than or equal to 34 weeks estimated gestational age with preterm labor or premature rupture of membranes underwent amniocentesis to detect subclinical intraamniotic infection. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as for Mycoplasma species. Amniotic fluid glucose levels were significantly lower in patients with positive amniotic fluid cultures than in patients with negative cultures (median, 10 mg/dl; range, 1 to 62 mg/dl vs median, 31 mg/dl; range, 2 to 126 mg/dl, respectively; p less than 0.001). In terms of predicting amniotic fluid culture results, an amniotic fluid glucose concentration of less than or equal to 16 mg/dl had a sensitivity of 79%, specificity of 94%, positive predictive value of 87%, and negative predictive value of 90%. The determination of amniotic fluid glucose concentration is useful in detecting subclinical intraamniotic infection in patients less than or equal to 34 weeks estimated gestational age with preterm labor or premature rupture of membranes.

Acute myocardial infarction associated with prostaglandin E2.

Prostaglandin E2 is rarely associated with serious maternal side effects when used for second-trimester pregnancy termination. Acute myocardial infarction complicating therapeutic pregnancy termination with prostaglandin E2 in a patient with chronic glomerulosclerosis and severe hypertension is reported.