Lung maturity tests. Relation to source, clarity, gestational age and neonatal outcome

OBJECTIVE

To determine whether gestational age is a significant determinant of neonatal outcome, irrespective of biochemical lung maturity. The effects of specimen source and clarity on the reliability of biochemical tests for predicting respiratory distress syndrome are also evaluated.

STUDY DESIGN

Perinatal outcome was analyzed for 904 neonates undergoing amniotic fluid maturity studies within three days of delivery from 1991 to 1993. The relationships of gestational age and biochemical maturity to neonatal outcome were examined using multivariate analysis of covariance. Test reliability was evaluated using log-linear analysis of multiway frequency tables.

RESULTS

Gestational age was a better predictor of neonatal outcome than biochemical lung maturity. Gestational age significantly correlated with every measure of outcome except intraventricular hemorrhage and jaundice. Test reliability was not significantly influenced by specimen source or clarity.

CONCLUSION

Results obtained using contaminated amniotic fluid are reliable when the proper technique is used. Irrespective of biochemical maturity, neonatal outcome is significantly related to gestational age. Gestational age, and not just biochemical maturity, should be considered when timing delivery.

The preterm prediction study: a clinical risk assessment system

OBJECTIVE

Our aims were to develop a risk assessment system for the prediction of spontaneous preterm delivery using clinical information available at 23 to 24 weeks' gestation and to determine the predictive value of such a system.

STUDY DESIGN

A total of 2929 women were evaluated between 23 and 24 weeks' gestation at 10 centers. Demographic factors, socioeconomic status, home and work environment, drug and alcohol use, and medical history were evaluated. Information regarding symptoms, cultures, and treatments in the current pregnancy were ascertained. Anthropomorphic and cervical examinations were performed. Univariate analysis and multivariate logistic regression were performed in a random selection, constituting 85% of the study population. The derived risk assessment system was applied to the remaining 15% of the population to evaluate its validity.

RESULTS

A total of 10.4% of women were delivered of preterm infants. The multivariate models for spontaneous preterm delivery were highly associated with spontaneous preterm delivery (p < 0.0001). A low body mass index (<19.8) and increasing Bishop scores were significantly associated with spontaneous preterm delivery in nulliparous and multiparous women. Black race, poor social environment, and work during pregnancy were associated with increased risk for nulliparous women. Prior obstetric outcome overshadowed socioeconomic risk factors in multiparous women with a twofold increase in the odds of spontaneous preterm delivery for each prior spontaneous preterm delivery. Current pregnancy symptoms, including vaginal bleeding, symptomatic contractions within 2 weeks, and acute or chronic lung disease were variably associated with spontaneous preterm delivery in nulliparous and multiparous women. When the system was applied to the remainder of the population, women defined to be at high risk for spontaneous preterm delivery (> or = 20% risk) carried a 3.8-fold (nulliparous women) and 3.3-fold (multiparous women) higher risk of spontaneous preterm delivery than those predicted to be at low risk. However, the risk assessment system identified a minority of women who had spontaneous preterm deliveries. The sensitivities were 24.2% and 18.2% and positive predictive values were 28.6% and 33.3%, respectively, for nulliparous and multiparous women.

CONCLUSIONS

Although it is possible to develop a graded risk assessment system that includes factors that are highly associated with spontaneous preterm delivery in nulliparous and multiparous women, such a system does not identify most women who subsequently have a spontaneous preterm delivery. This system has investigational value as the basis for evaluating new technologies designed to identify at-risk subpopulations.

Brain natriuretic peptide and cyclic guanosine-3',5' monophosphate in pre-eclampsia

The objective of this study is to determine the possibility that pre-eclampsia, a disease characterized by altered vascular tone, may result in altered levels of fetal BNP and cGMP, and to determine whether pre-eclampsia alters the maternal-fetal relationship of BNP and cGMP. Paired maternal and umbilical venous plasma levels of BNP and cGMP were determined in 13 pre-eclamptic and 9 normotensive primigravidas in the third trimester. Statistical analysis was performed using multivariate analysis of variance, linear regression, and canonical correlation. Overall, levels of cGMP were lower in pre-eclampsia (P < 0.03). Pre-eclampsia was also associated with an altered maternal-fetal relationship for BNP and cGMP (P < 0.008, P < 0.02, respectively). With pre-eclampsia, the maternal:fetal ratio was reduced for BNP and was increased for cGMP. Because of its role as a second messenger for many vasoactive hormones, we hypothesize that fetal cGMP levels may better reflect overall vascular tone than do individual hormones. Altered BNP and cGMP maternal-fetal homeostasis raises the possibility of maternal-fetal coordination of vascular control.

Changes in health care delivery: a threat to academic obstetrics

OBJECTIVE

Our purpose was to examine the effect of anticipated health care policy changes on delivery trends at leading academic obstetric institutions.

STUDY DESIGN

The 51 centers in the United States with the most Society of Perinatal Obstetricians presentations in the past 2 years were surveyed regarding annual deliveries from 1990 to 1993 and reasons for any changes. Analysis of variance and chi 2 analysis were used as appropriate.

RESULTS

Complete data were available from 43 hospitals representing 39 institutions. Their 1990 to 1993 delivery rates declined faster than United States delivery rates (12.3% vs 2.0%, p < 0.0001). The largest hospitals (> 6000 deliveries) had a decline of 18.2% compared with declines of 9.0% for medium and 0.9% for small hospitals (< 2500 deliveries). Regionally the greatest impact was seen in the West and the South, with 22% and 12% declines, respectively (p < 0.05). Reasons cited for the decline included competition from private or community physicians or hospitals (59%) and managed care (15%).

CONCLUSION

As the national health care debate focuses on cost containment and coverage, we believe the potential effects of national policy on research and education should be considered. Continued selective reduction in deliveries at academic institutions can be expected to adversely affect research and education.

Computer-generated admission forms have greater accuracy

We examined the accuracy of computer-generated admission forms to standardized handwritten admission forms for 40 patient records. There was a mean of 8.3 errors among handwritten forms but only 0.9 errors among computerized forms (p < 0.0001). Written forms had seven serious errors versus one for computerized forms (p < 0.05). We conclude that computerized admission forms have superior accuracy.

Underappreciated risks of the elderly multipara

OBJECTIVE

Our purpose was to identify the age-related increased risks of the elderly gravida by clarifying the effects of age and parity, their combination, and their interaction.

STUDY DESIGN

We studied 9556 singleton pregnancies in women aged 20 to 29 years or > or = 35 years delivered over an 8-year period. Data were analyzed by stepwise multiway contingency table analysis, with p < 0.002 considered significant.

RESULTS

Many of the previously reported risks of the elderly gravida are expected on the basis of age and parity. Significant associations (primarily related to advanced age) included higher frequencies of obesity, chronic hypertension, gestational diabetes, and large-for-gestational-age and macrosomic infants. These elderly gravidas, on the other hand, had fewer postdates pregnancies. Although often overlooked, the greatest age-related increases in risk for induction (1.8 times), preeclampsia (2.7 times), gestational diabetes (4.5 times), clinical diabetes (3.2 times), oxytocin use (1.7 times), and macrosomia (1.6 times) occur in multiparas, not nulliparas. The risk for preeclampsia in the elderly multipara is significantly higher than expected on the basis of age and parity.

CONCLUSION

The increased risks of the elderly multipara may have been overshadowed by the previous focus on the elderly nullipara. It is important to recognize the increases in age-related risks of the elderly multipara to appropriately counsel and manage this group of patients.

Maternal syphilis in Michigan: the challenge to prevent congenital syphilis

Syphilis has re-emerged as a significant public health problem for pregnant women and their babies in Michigan, US, and in many areas of the world. In the US over 50,000 cases of primary and secondary syphilis were reported to the Centers for Disease Control (CDC) in 1990. Due to the current epidemic of maternal syphilis in pregnancy in our city, we studied 253 cases of maternal syphilis over a one-year period. Our objective was to determine maternal risk factors during pregnancy predicting congenital infection. Women with high venereal disease research laboratory (VDRL) titres during pregnancy and unknown duration of disease had the highest incidence of delivering an infant with congenital syphilis. Even with treatment according to the current CDC guidelines there was a 27% incidence of congenital syphilis if disease duration was < 1 year and a 49% incidence of congenital syphilis for unknown duration of disease. Maternal syphilis during pregnancy was associated with significant neonatal morbidity and a preterm delivery incidence of 28%. The clinical evaluation, management, and current treatment guidelines are reviewed in this paper.

Comparison of intrauterine hematologic and biochemical values between twin pairs with and without stuck twin syndrome

OBJECTIVE

Our purpose was to compare hematologic and biochemical values in cordocentesis specimens from twin pairs with and without stuck twin syndrome.

STUDY DESIGN

Cordocentesis was performed on 38 twin pairs. Assignment to the stuck twin syndrome group (n = 8) was based on ultrasonographic findings of discordant size and amniotic fluid volume, concordant gender, and a single placenta. A receiver-operator characteristic curve was constructed with the use of intertwin hemoglobin differences. For the stuck twin syndrome group regression analysis of gestational age and intertwin hemoglobin difference was done.

RESULTS

We found significant (p = 0.03) intertwin differences in hemoglobin between the stuck twin syndrome group (mean 5.35 gm/dl, range 0.5 to 15.4 gm/dl) and the comparison group (mean 0.10 gm/dl, range 0.0 to 2.4 gm/dl). A nearly significant relationship between gestational age and intertwin hemoglobin difference was noted in the stuck twin syndrome group. When the hemoglobin difference was > 2.4 gm/dl, all cases had stuck twin syndrome (sensitivity = 50%, specificity = 100%, positive predictive value = 100%, negative predictive value = 91%). In the stuck twin syndrome group there was a trend toward larger intertwin differences in albumin and total protein. Intertwin blood gas values between the groups did not differ, but the average PO2 was lower when the smaller twins of the two groups were compared.

CONCLUSION

An intertwin difference in hemoglobin > 2.4 gm/dl is consistent with stuck twin syndrome. Large intertwin hemoglobin differences and imbalances in albumin and total protein may be seen in stuck twin syndrome.

Centile-based ultrasound morphometric tables

Current ultrasound morphometric tables estimate centiles assuming normal distribution and similar variation throughout gestation. Our goal was to develop normative tables for biparietal diameter, femur length and average abdominal diameter using actual centiles. We studied the last complete ultrasound examination from 9510 singleton, live pregnancies without major malformations delivered at our hospital. Actual 5th, 10th, 50th, 90th and 95th centiles were calculated for each week and compared to estimates based on means and standard deviations. With advancing gestational age, variation in average abdominal diameter increased and variation in biparietal diameter and femur length remained stable. The largest difference between an actual and an estimated centile limit was 2 mm for biparietal diameter or femur length and 3 mm for average abdominal diameter. Differences between true and estimated centile limits were less than the intraobserver variation of the ultrasound measurements and therefore clinically unimportant.

Third stage of labor: analysis of duration and clinical practice

OBJECTIVES

Our purpose was to record gestational age-specific data for third-stage duration of labor, frequencies of retained placentas (undelivered at 30 minutes), manual removal of the placenta, and hemorrhage.

STUDY DESIGN

Included were 45,852 singleton deliveries > or = 20 weeks' gestation from 1984 to 1992. Odds ratios, 95% confidence intervals, and actuarial life analysis with censoring of cases with manual placenta removal were performed.

RESULTS

The frequency of retained placentas (2.0% overall) was markedly increased among gestations < or = 26 weeks (odds ratio 20.8, 95% confidence interval 17.1 to 25.4) and < 37 weeks (odds ratio 3.0, 95% confidence interval 2.6 to 3.5) compared with term. The frequency of manual removal (3.0% overall) was increased among gestations < or = 26 weeks (odds ratio 9.2, 95% confidence interval 7.5 to 11.4) and < 37 weeks (odds ratio 2.8, 95% confidence interval 2.4 to 3.1) compared with term. Hemorrhage (3.5% overall) was increased among subjects with manual placenta removal (odds ratio 10.4, 95% confidence interval 9.1 to 11.9); hemorrhage was also increased among gestations < or = 26 weeks (odds ratio 3.0, 95% confidence interval 2.3 to 4.0) and < 37 weeks (odds ratio 1.2, 95% confidence interval 1.01 to 1.3) compared with term. The frequency of hemorrhage peaked by 40 minutes regardless of gestational age. Life-table analysis predicted 90% of placentas would spontaneously deliver by 180 minutes for gestations at 20 weeks, 21 minutes at 30 weeks, and 14 minutes at 40 weeks; the predicted frequency of retained placentas was 42% higher than the recorded incidence.

CONCLUSIONS

The duration of the third stage decreases and the frequencies of hemorrhage and manual removal decrease with increasing gestational age. Hemorrhage was associated with manual placental removal. Life-table analysis indicated that manual removal of placentas shortened the duration of the third stage of labor, especially among preterm deliveries. A prospective trial is needed to determine whether manual placental removal can reduce hemorrhage among prolonged third stages.

Perinatal outcome of broken marriage in the inner city

OBJECTIVE

To test the hypothesis that the erosion of family structure, epidemic substance abuse, and increased low birth weight (LBW) rates are interrelated.

METHODS

In this cohort study, we analyzed information coded prospectively in a computerized perinatal data base. Separated, divorced, and widowed mothers were grouped as broken marriages. The setting was a predominantly urban, indigent population in a tertiary care hospital. The analysis included singleton pregnancies of 14,896 women receiving prenatal and intrapartum care at our hospital from 1986-1991. The main outcome measures included LBW, prematurity, small for gestational age, neonatal mortality, and neonatal intensive care unit admissions.

RESULTS

Married mothers fared better than single mothers, but risks for adverse perinatal outcomes for women with broken marriages were consistently as high or higher than for single mothers. The rate of LBW infants was 43% higher in the broken marriage group than in the married group. The increased frequency of LBW among infants born into broken marriages was attributable mainly to reduced growth rather than to prematurity and was associated with substance abuse.

CONCLUSION

Our findings indicate that mothers from broken marriages are at relatively higher risk for LBW infants than married mothers (odds ratio 1.5). Broken marriage warrants emphasis as an important perinatal risk factor.

Amnioinfusion: does the choice of solution adversely affect neonatal electrolyte balance?

OBJECTIVE

To determine whether various solutions commonly used in amnioinfusion during labor affect neonatal electrolyte and blood gas values.

METHODS

Amnioinfusion for thick meconium or severe variable fetal heart rate decelerations is used at our institution according to a standardized protocol. During alternating 3-week periods, the only solution made available for amnioinfusion was either normal saline or Ringer's lactate. Bolus volume, rate, and duration of infusion were determined by the individual physicians. At delivery, cord blood was collected for electrolyte and blood gas determination. These values were compared between the two solution groups and to a non-infused control group.

RESULTS

Complete data on neonatal electrolytes and blood gas values were available on 53 infusion patients (20 Ringer's lactate, 33 normal saline) and 39 non-infusion patients. Comparing infusion to non-infusion patients and those infused with Ringer's lactate to those with normal saline, we found no significant difference in demographics, neonatal outcome variables, duration of labor, neonatal electrolytes, and cord blood gas values. Infusion variables (bolus volume, infusion rate, hours infused, and total volume infused) did not differ between solutions. Total volume and hours of infusion were closely correlated with each other (r = 0.93, P < .001); both were correlated with neonatal chloride (r = 0.38 and r = 0.36, respectively; P < .005). No cases of hypernatremia or hyperchloremia were found in any of the groups. The type of solution used had no effect on the neonatal chloride trend.

CONCLUSION

The use of both normal saline and Ringer's lactate for indicated amnioinfusion in labor appears to have no clinically significant effect on neonatal electrolytes.

Hemostasis and diagnosis of preeclampsia

The diagnosis of preeclampsia, with all of its consequences, is at times difficult to establish, especially when the patient has underlying chronic hypertension and is not known from prior prenatal care visits. Many screening tests have been proposed. These should be sensitive, relatively specific, easy to perform, of low cost, and have a reasonable interval from prediction to disease onset. Laboratory assays would obviously be useful. We evaluated hemostasis tests for the diagnosis of preeclampsia, and compared fibronectin, antithrombin III and alpha 2-antiplasmin in 48 preeclamptics and 86 control nulliparas. Receive operator characteristic (ROC) curve analysis suggested that fibronectin is the most effective of these tests. A similar analysis comparing the results of previous studies using serum iron, angiotensin infusion, urinary calcium/creatinine ratio, the rollover test and uric acid suggested a possible role for fibronectin in the diagnosis of preeclampsia. While not ideal, there seems to be, at present, no other, easy to perform laboratory test that outperforms fibronectin in predicting preeclampsia.

Epidemic syphilis: maternal factors associated with congenital infection

OBJECTIVE

Little is known about which cases of maternal syphilis will affect the newborn. Because of the current epidemic of syphilis in pregnancy in our city, we sought to identify risk factors during pregnancy associated with congenital infection.

STUDY DESIGN

We reviewed 253 cases of maternal syphilis prospectively identified over a 1-year period. On the basis of neonatal diagnosis, these data were divided into two groups, those without evidence of presumptive congenital syphilis and those with evidence of presumptive congenital syphilis. Presumptive congenital syphilis was defined according to the Centers for Disease Control and Prevention surveillance case definition. Cases with bloody spinal taps and cases of suspected congenital syphilis that did not meet these criteria were excluded. Venereal Disease Research Laboratory titers are given as the inverse of the geometric mean.

RESULTS

Venereal Disease Research Laboratory titer at time of diagnosis and unknown duration of disease were risk factors for congenital syphilis. There was a significantly decreased rate of congenital syphilis with single-dose therapy if disease length was < 1 year (p < 0.005). Unknown duration of disease was associated with 67.9% and 48.6% rates of congenital syphilis with one- and three-dose therapy respectively. There was a 28% incidence of preterm birth.

CONCLUSION

Our study suggests an alarming rate of failure of current therapy to prevent congenital syphilis. Venereal Disease Research Laboratory titer at time of diagnosis and unknown duration of disease are risk factors for congenital syphilis. The high rate of presumptive congenital syphilis in the unknown duration group indicates that identification before or earlier in pregnancy will be necessary to prevent devastating consequences for the neonate.

Accelerated pulmonary maturation from preterm premature rupture of membranes: a myth

OBJECTIVES

It is widely believed that premature rupture of membranes accelerates fetal pulmonary maturity. The purpose of our study was to determine the duration of premature rupture of the membranes required to achieve this effect.

STUDY DESIGN

Retrospective analysis of our database yielded a group of 1395 patients who were delivered between 24 and 35 weeks' gestation and for whom we had complete data. The frequencies of premature rupture of the membranes and respiratory distress syndrome by each gestational week were analyzed with a log linear multiway contingency table analysis. Because gestational age was based on pediatric examination and was therefore somewhat subjective, birth weight was used to confirm results. Additional factors related to respiratory distress syndrome were considered in stepwise discriminant analysis. Results were further verified by the 1980 National Natality Survey data set.

RESULTS

When we controlled for either gestational age or birth weight, there was no significant difference in the frequency of respiratory distress syndrome related to premature rupture of the membranes, but there was a suggestion (p < 0.08) that respiratory distress syndrome was actually more frequent after premature rupture of the membranes. Stepwise discriminant analysis revealed that gestational age, birth weight, race, sex, and Apgar score at 1 minute were all more important determinants than duration of premature rupture of the membranes. Duration of premature rupture of the membranes was associated with an increased risk of respiratory distress syndrome. Amnionitis was found to be highly related to the duration of premature rupture of the membranes. The incidence of amnionitis significantly increased 24 hours after premature rupture of the membranes occurred. A multiway frequency contingency table of the National Natality Survey data showed a significant increase in respiratory distress syndrome in association with premature rupture of the membranes.

CONCLUSIONS

Pulmonary maturation continues but is not accelerated after premature rupture of the membranes. In fact, there is a strong suggestion that premature rupture of the membranes actually increases the risk of respiratory distress syndrome at a given gestational age.

Single umbilical artery: accurate diagnosis?

OBJECTIVE

We sought to evaluate the accuracy of ultrasonographic, obstetric, and neonatal diagnosis of a single umbilical artery.

STUDY DESIGN

We studied 17,777 consecutive singleton births from women who had undergone ultrasonographic examination at our hospital. A single umbilical artery was confirmed in 37 cases (0.2%) by two clinical methods or by pathologic assessment. Outcome of neonates with a single umbilical artery was compared with the outcome of neonates with either two or three vessel cords.

RESULTS

Ultrasonographic diagnosis had a 65% sensitivity and positive predictive value. Obstetricians and pediatricians failed to diagnose 24% and 16% of the cases, respectively. On average, neonates with a single umbilical artery weighed 320 gm less, were delivered 1 week earlier, and had lower Apgar scores than neonates with three vessel cords (p < 0.01 in each case.)

CONCLUSION

Although early gestational age may account for some cases not diagnosed by ultrasonography, there is a little justification for missing the diagnosis after delivery. Greater emphasis on clinical examination of the umbilical cord is needed to identify neonates at risk of associated malformations.

Ultrasonographic prediction of neonatal survival in extremely low-birth-weight infants

OBJECTIVE

Our purpose was to improve the accuracy of prenatal prognostication by directly correlating obstetric ultrasonographic measurements with neonatal survival.

STUDY DESIGN

We studied 130 singleton live-born infants with birth weights between 500 and 1000 gm and who underwent complete ultrasonographic examinations within 3 days of delivery. Ultrasonographic measurements were evaluated as screening tests for neonatal survival by means of receiver-operator characteristic curves and compared with birth weight and pediatric assessment of gestational age.

RESULTS

Eighty infants survived, and 50 died. Visual inspection of the receiver-operator characteristic curves indicated that biparietal diameter was the best predictor of survival. While correctly identifying all survivors, biparietal diameter predicted nonsurvivors better (p < 0.0001) than did actual birth weight or any other variable.

CONCLUSION

Our findings indicate that using biparietal diameter to determine neonatal prognosis is significantly more reliable than the current practice of using estimated fetal weight. We speculate that biparietal diameter may reflect maturity more accurately because it is less subject to variation in growth.

Amniotic fluid platelet factor 4 and beta-thromboglobulin

Platelet activating factor (PAF), a powerful platelet activator, has been identified in human embryos and fetuses, and may induce fetal lung maturation. The potential effect of PAF on fetal platelets as indicated by release of beta-thromboglobulin (BTG) and platelet factor 4 (PF4) has not been investigated. We measured BTG and PF4 in amniotic fluid from 78 genetic and 35 pulmonary maturity amniocenteses. BTG and PF4 were higher in the genetic amniocentesis samples (p < 0.001 in each case) than in the lung maturity samples. BTG and PF4 did not correlate with the pulmonary maturity parameters as measured by the lecithin to sphingomyelin ratio and phosphatidylglycerol concentration. Our findings suggest a fetal origin of BTG and PF4 in amniotic fluid.

Trends in sonographic fetal organ visualization

In order to assess changes in sonographic visualization over the last 6 years, 7092 second- and third-trimester ultrasound examinations from separate pregnancies in three individual years (1451 in 1985, 3016 in 1988, and 2625 in 1991) were compared. Overall, visualization across all gestational ages improved from 63.9% (1985) to 85.8% (1988) to 87.3% (1991), with the year in which the scan was performed explaining 19.6% of the variance in visualization. Maternal size (as determined by body mass index) remained the major determinant of ultrasound visualization in 1991 (r(2) = 11.2%), with gestational age explaining only 5.2% additional variance. Overall organ visualization was maximal at 21-23 weeks' gestation, with the decline in later gestation primarily accounted for by worsened visualization of fetal extremities and spine. Improved fetal visualization earlier in the second trimester and the advent of embryonic visualization in the first trimester may allow a continuum of prenatal sonographic diagnosis.

Markers for endothelial injury, clotting and platelet activation in preeclampsia

The etiology of disseminated intravascular coagulation (DIC) in preeclampsia is not well understood. We measured plasma levels of fibronectin (FN), which may reflect endothelial cell injury, fibrinopeptide A (FPA), a specific marker of clotting, platelet counts (PLC) and mean platelet volumes (MPV), as well as beta-thromboglobulin (beta TG) and platelet factor 4 (Pf4), products of irreversible platelet activation in 24 preeclamptic patients and 24 controls matched for age, gestational age, labor status, and parity. In preeclampsia, FN and FPA were significantly elevated while PLC were significantly decreased (P less than 0.0001, less than 0.05 and less than 0.01, respectively). beta TG, Pf4, and MPV values did not show significant differences. These findings support the hypothesis that endothelial injury, clotting activation and platelet consumption are increased in preeclampsia. However, the much closer association of preeclampsia with FN levels as compared to FPA, beta TG, Pf4, suggests that endothelial injury is a more basic mechanism of preeclampsia than clotting or platelet activation.