Letters

Volume 163 Number 1, Part I

ence of meconium below vocal cords. It is therefore exciting to me that the rate of meconium below vocal cords could be reduced to 0% by the combination of amnioinfusion and DeLee airway suctioning. These findings truly support the hypothesis that the majority of the cases of meconium aspiration occur "in utero" and before the first breath. If this is the case then meconium aspiration syndrome is as difficult to prevent as fetal distress. Yeomans et al" found that meconiumstained amniotic fluid correlates poorly with the infant's condition at birth as reflected by umbilical cord pH. The "bottom line" is that when a case of meconiumstained amniotic fluid is encountered, the current state of the art does not allow us to predict which infants will develop meconium aspiration syndrome. In this stagnated research field of meconium aspiration syndrome, amnioinfusion offers hope. We agree with the authors that the true test will come when amnioinfusion is proved to reduce the rate of symptomatic meconium aspiration syndrome. Hypothetically, if these findings were corroborated by other investigators with a larger sample of patients, then further questions remain. (1) How aggressive will we need to be in detecting the presence of meconium in the absence of labor and intact membranes? (2) Should we use the technique of amnioscopy in patients at high risk for meconium-stained amniotic fluid? (3) How soon should amnioinfusion be started after meconium is detected into the amniotic fluid? And finally (4) will amnioinfusion affect the outcome of infants who already had meconium below vocal cords at the beginning of the procedure? Horacio Sergio Falciglia, MD Department of Pediatrics, Good Samaritan Hospital, Cincinnati, OH 45220

REFERENCES 1. Carson BS, Fosey RW, Bowls WA, et al. Combined obstetric and pediatric approach to prevent meconium aspiration syndrome. AM J OBSTET GYNECOL 1976;126:712-5. 2. Faiciglia HS. Failure to prevent meconium aspiration syndrome. Obstet Gynecol 1988;71 :349-53. 3. Dooley S, Pesavento D, Depp R, et al. Meconium below the vocal cords at delivery: correlation with intrapartum events. AMJ OBSTET GYNECOL 1985;153:767-70. 4. Yeomans E, Gilstrap L, Leveno K, et al. Meconium in the amniotic fluid and fetal acid-base status. Obstet Gynecol 1989;73: 175-8.

Reply To the Editors: We thank Dr. Falciglia for his important

comments. Indeed, once the amniotic fluid is stained with meconium, aspiration can occur antepartum, intrapartum, or during the infant's first few breaths after delivery. Only the effect of the latter mechanism can be ameliorated by DeLee suctioning as described by Carson et al. I Amnioinfusion may decrease the risk of intrapartum aspiration, but will not prevent aspiration that occurred before labor or before the start of the amnioinfusion. We believe that by utilizing this technique further observations may help identify those fetuses who have aspirated meconium before amnioinfusion.

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We concur with Dr. Falciglia that certain questions remain unanswered. The appropriate role of prenatal diagnosis of meconium-stained amniotic fluid is yet undetermined. To optimize the efficacy of amnioinfusion, it should be initiated as soon as possible after the intrapartum diagnosis of the presence of meconium. We agree with Dr. Falciglia that a larger sample of patients is needed to confirm our findings. Although we think that intrapartum amnioinfusion has the potential to decrease the risk of meconium aspiration, this technique should not be regarded as standard obstetric care by the medical community at large until further research demonstrates the safety of this procedure. Yoel Sadovsky, MD Washington University Medical Center, 4911 Barnes Hospital P law, St. Louis, MO 63110

Eral Amon, MD University of Tennessee, Memphis, 869 Madison Ave., Memphis, TN 38103-3433

REFERENCE I. Carson BS, Losey RW, Bowes WA, et al. Combined obstetric and pediatric approach to prevent meconium aspiration syndrome. AM] OBSTET GYNECOL 1983;146:670-8.

Use of serial human chorionic gonadotropin measurements to differentiate between intrauterine and ectopiC pregnancies To the Editors: I read the article by Lindblom et al. (Lindblom B, Hahlin M, Sjoblom P. Serial human chorionic gonadotropin determinations by fluoroimmunoassay for differentiation between intrauterine and ectopic gestation. AM J OBSTET GYNECOL 1989;161:397) with some bemusement. My colleagues and I showed almost 10 years ago that when serial human chorionic gonadotropin (hCG) monitoring was restricted to a group of patients roughly similar to that studied by Lindblom et al. (our patients were symptomatic whereas those of Lindblom et al. were not) the slope of the log hCGtime regression line provided a useful method of differentiating between symptomatic intrauterine and ectopic pregnancies when other tests, such as ultrasonography and culdocentesis, were nondiagnostic. We estimated the 15th percentile of the distribution of the slope of this regression line to be 0.25 among women with symptomatic but viable intrauterine pregnancies (when natural logarithms were used), and found that the value for the slope was less than this in 87% of women with ectopic pregnancies. I It is salutory to note (although Lindblom et al. failed to point this out) how well these authors' findings agree with our original results, especially because they excluded patients with falling serum hCG values. By our criterion, 17/ 19 (89%) of their patients with ectopic pregnancies were identified as abnormal, and the falsepositive rate was 18% or 27%, depending on whether one wishes to classify cases 23 and 31 (slopes, 0.248) as normal or abnormal. In either event, the difference between these values and our original figures is easily accounted for by sampling variation.

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Letters

Since our early publications, Pitta way et al! have questioned whether the rate of increase in heG during the first 6 weeks of pregnancy is truly exponential as it was originally shown to be by Marshall et aI.' However, Daya4 and Fritz and Guo; have since resolved this question by showing that the log heG-time relationship is adequately represented by a linear regression line when heG values are

Use of serial human chorionic gonadotropin measurements to differentiate between intrauterine and ectopic pregnancies.

Letters Volume 163 Number 1, Part I ence of meconium below vocal cords. It is therefore exciting to me that the rate of meconium below vocal cords c...
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