Increased sensitivity to angiotensin II is present postpartum in women with a history of hypertensive pregnancy

Pregnancies complicated by new-onset hypertension are associated with increased sensitivity to angiotensin II, but it is unclear whether this sensitivity persists postpartum. We studied pressor response to infused angiotensin II in 25 normotensive postpartum women in both high- and low-sodium balance. Ten women had a history of hypertensive pregnancy (5 with preeclampsia; 5 with transient hypertension of pregnancy), and 15 women had a history of uncomplicated, normotensive pregnancy. Systolic and diastolic blood pressures, aldosterone, and soluble fms-like tyrosine kinase 1 levels were measured before and after angiotensin II infusion in both dietary phases. In high sodium balance, women with a history of hypertensive pregnancy were normotensive but had significantly higher systolic and diastolic blood pressures than controls (115 versus 104 mm Hg and 73 versus 65 mm Hg, respectively; P<0.05). Women with a history of hypertensive pregnancy had a pressor response to salt loading, demonstrated by an increase in systolic blood pressure on a high-salt diet. They also had greater systolic pressor response (10 versus 2 mm Hg; P=0.03), greater increase in aldosterone (56.8 versus 30.8 ng/dL; P=0.03), and increase in soluble fms-like tyrosine kinase 1 levels (11.0 versus -18.9 pg/mL; P=0.02) after infusion of angiotensin II in low-sodium balance compared with controls. Thus, women with a history of hypertensive pregnancy demonstrated salt sensitivity of blood pressure and had increased pressor, adrenal, and soluble fms-like tyrosine kinase 1 responses to infused angiotensin II in low-sodium balance. Increased sensitivity to angiotensin II observed during pregnancy in women with hypertensive pregnancy is present postpartum; this feature may contribute to future cardiovascular risk in these women.

Preeclampsia: 2-methoxyestradiol induces cytotrophoblast invasion and vascular development specifically under hypoxic conditions

Inadequate invasion of the uterus by cytotrophoblasts is speculated to result in pregnancy-induced disorders such as preeclampsia. However, the molecular mechanisms that govern appropriate invasion of cytotrophoblasts are unknown. Here, we demonstrate that under low-oxygen conditions (2.5% oxygen), 2-methoxyestradiol (2-ME), which is a metabolite of estradiol and is generated by catechol-o-methyltransferase (COMT), induces invasion of cytotrophoblasts into a naturally-derived, extracellular matrix. Neither low-oxygen conditions nor 2-ME alone induces the invasion of cytotrophoblasts in this system; however, low-oxygen conditions combined with 2-ME result in the appropriate invasion of cytotrophoblasts into the extracellular matrix. Cytotrophoblast invasion under these conditions is also associated with a decrease in the expression of hypoxia-inducible factor-1alpha (HIF-1alpha), transforming growth factor-beta3 (TGF-beta3), and tissue inhibitor of metalloproteinases-2 (TIMP-2). Pregnant COMT-deficient mice with hypoxic placentas and preeclampsia-like features demonstrate an up-regulation of HIF-1alpha, TGF-beta3, and TIMP-2 when compared with wild-type mice; normal levels are restored on administration of 2-ME, which also results in the resolution of preeclampsia-like features in these mice. Indeed, placentas from patients with preeclampsia reveal lower levels of COMT and higher levels of HIF-1alpha, TGF-beta3, and TIMP-2 when compared with those from normal pregnant women. We demonstrate that low-oxygen conditions of the placenta are a critical co-stimulator along with 2-ME for the proper invasion of cytotrophoblasts to facilitate appropriate vascular development and oxygenation during pregnancy.

Maternal antenatal complications and the risk of neonatal cerebral white matter damage and later cerebral palsy in children born at an extremely low gestational age

In a 2002-2004 prospective cohort study of deliveries of infants at <28 weeks at 14 US centers, the authors sought the antecedents of white matter damage evident in newborn cranial ultrasound scans (ventriculomegaly and an echolucent lesion) and of cerebral palsy diagnoses at age 2 years. Of the 1,455 infants enrolled, those whose mothers received an antenatal steroid tended to have lower risks of ventriculomegaly and an echolucent lesion than their peers (10% vs. 23%, P < 0.001 and 7% vs. 11%, P = 0.06, respectively). Risk of ventriculomegaly was increased for infants delivered because of preterm labor (adjusted odds ratio (OR) = 2.3, 95% confidence interval (CI): 1.1, 4.9), preterm premature rupture of fetal membranes (OR = 3.6, 95% CI: 1.5, 8.7), and cervical insufficiency (OR = 2.8, 95% CI: 1.4, 5.5) when compared with infants delivered because of preeclampsia. Risk of an echolucent lesion was increased for infants delivered because of preterm labor (OR = 2.7, 95% CI: 1.2, 5.7) and intrauterine growth retardation (OR = 3.3, 95% CI: 1.2, 9.4). The doubling of diparesis risk associated with preterm labor and with preterm premature rupture of fetal membranes did not achieve statistical significance, nor did the doubling of quadriparesis risk and the tripling of diparesis risk associated with cervical insufficiency.

Invited commentary: Intrauterine epidemiology

Traditionally, the investigation of preterm birth has relied on diagnostic definitions derived from maternal clinical presentation. However, clinical presentation may be only tangentially related to the underlying etiology of a disease. The utilization of data derived directly from the intrauterine or maternal systemic environment would be invaluable in consideration of the causes of preterm birth. In this issue, Kelly et al. (Am J Epidemiol. 2009;170(2)148-158) contribute to our understanding of the epidemiology of the intrauterine environment by classifying the vascular biology of the maternal-placental interface in cases of preterm delivery. Their histology-based approach observes that vascular conditions may be grouped into 5 constructs with specific relations to maternal and fetal vascular pathology. The frequencies of these constructs vary with regard to delivery indication and gestational age, suggesting that the intrauterine conditions associated with preterm birth are more complicated than originally appreciated. This work is laborious, and replication of the technique will be important. However, these authors have taken a large step toward introducing an "intrauterine" perspective into perinatal epidemiology and into our understanding of the underlying etiologies of preterm birth.

Pregnancy disorders that lead to delivery before the 28th week of gestation: an epidemiologic approach to classification

Epidemiologists have grouped the multiple disorders that lead to preterm delivery before the 28th week of gestation in a variety of ways. The authors sought to identify characteristics that would help guide how to classify disorders that lead to such preterm delivery. They enrolled 1,006 women who delivered a liveborn singleton infant of less than 28 weeks' gestation at 14 centers in the United States between 2002 and 2004. Each delivery was classified by presentation: preterm labor (40%), prelabor premature rupture of membranes (23%), preeclampsia (18%), placental abruption (11%), cervical incompetence (5%), and fetal indication/intrauterine growth restriction (3%). Using factor analysis (eigenvalue = 1.73) to compare characteristics identified by standardized interview, chart review, placental histology, and placental microbiology among the presentation groups, the authors found 2 broad patterns. One pattern, characterized by histologic chorioamnionitis and placental microbe recovery, was associated with preterm labor, prelabor premature rupture of membranes, placental abruption, and cervical insufficiency. The other, characterized by a paucity of organisms and inflammation but the presence of histologic features of dysfunctional placentation, was associated with preeclampsia and fetal indication/intrauterine growth restriction. Disorders leading to preterm delivery may be separated into two groups: those associated with intrauterine inflammation and those associated with aberrations of placentation.

Colonization of second-trimester placenta parenchyma

OBJECTIVE

The overtly healthy, nonpregnant uterus harbors bacteria, Mycoplasma and Ureaplasma. The extent of colonization remains elusive, as are relationships between isolated microorganisms, preterm labor and fetal inflammation.

STUDY DESIGN

Biopsy specimens of chorion parenchyma from 1083 placentas delivered before the beginning of the 28th week of gestation were cultured, and the placentas were examined histologically. The frequencies of individual microorganisms and groups of microorganisms were evaluated in strata of processes leading to preterm delivery, routes of delivery, gestational age, and placenta morphology.

RESULTS

Placentas delivered by cesarean section with preeclampsia had the lowest bacterial recovery rate (25%). Preterm labor had the highest rates, which decreased with increasing gestational age from 79% at 23 weeks to 43% at 27 weeks. The presence of microorganisms in placenta parenchyma was associated with the presence of neutrophils in the fetal stem vessels of the chorion or in the vessels of the umbilical cord.

CONCLUSION

The high rate of colonization appears to coincide with phenomena associated with preterm delivery and gestational age. The presence of microorganisms within placenta parenchyma is biologically important.

Validation of a Formula That Calculates the Estimated Risk of Respiratory Distress Syndrome

OBJECTIVE

Several groups, including ours, have developed probabilistic models that incorporate both the surfactant-to-albumin ratio (TDx-FLM II) and gestational age to more accurately predict the risk of neonatal respiratory distress syndrome (RDS) and eliminate the current categorical "immature"/"indeterminate"/"mature" interpretation. We validate our model using a separate data set, with the goal of providing the clinician with a risk score.

METHODS

The medical records of all women who had TDx-FLM II testing performed at Brigham and Women's Hospital between January 1, 2003, and December 31, 2005, were reviewed to gather a population upon which to validate our previous logistic regression model. Receiver operating characteristic curve and Hosmer-Lemeshow analysis was conducted to determine the performance of our model and another model in this new population.

RESULTS

A total of 233 mother-neonate pairs (21 RDS, 212 non-RDS) met criteria for analysis. The receiver operating characteristic analysis illustrated that our previous formula was a strong predictor of the risk of RDS with an area under the curve of 0.902 (95% confidence interval 0.849-0.955). In addition, using the Hosmer-Lemeshow analysis, our formula produced an excellent overall fit (P=.95), whereas another published model was a poor fit to our data (P=.002).

CONCLUSION

Our previously derived logistic regression model formula incorporating TDx-FLM II results and gestational age to predict risk of neonatal respiratory distress syndrome was robust and stable over time in an independent data set. The results suggest that the equation can be implemented clinically to assist physicians and patients and used by other institutions after their own internal validation.

LEVEL OF EVIDENCE

III.

Predictors of Compliance with the Postpartum Visit among Women Living in Healthy Start Project Areas

OBJECTIVES

Few studies have examined factors associated with compliance with a postpartum visit (PPV). The identification of such factors is of particular importance in populations with high rates of unintended pregnancies and medical complications of pregnancy. This study seeks to determine factors associated with compliance with a PPV among low-income women in the population served by fourteen Healthy Start sites.

METHODS

Data from the Healthy Start Survey of Postpartum Women were reviewed to identify variables associated with compliance with a PPV at or beyond 6 weeks. Multiple logistic regression models were created, based on a sociobehavioral model of health services use, to examine which types of factors (demographic, social, enabling or need) are most strongly associated with the use of a PPV.

RESULTS

The study population consisted of survey respondents interviewed six weeks or more following delivery. Eighty-five percent of respondents had had a PPV at time of interview. In a multiple regression analysis, enabling factors such as multiple moves (OR (95% CI)=0.34 (0.18, 0.67)), trouble understanding the provider (OR (95% CI)=0.65 (0.43, 0.99)) and appointment reminders (OR (95% CI)=2.37 (1.40, 4.02)) were most strongly associated with a PPV.

CONCLUSIONS

This work finds that women with unstable housing, transportation barriers, and difficulties communicating with providers are at risk for not receiving a PPV. This suggests that access to postpartum health services in the Healthy Start communities studied may not be entirely equitable. Policies aimed at improving interconception care will need to address these barriers to accessing health services.

The Use of Central Neuraxial Techniques in Parturients with Factor V Leiden Mutation

The factor V Leiden (FVL) mutation is a leading cause of thrombosis, particularly during pregnancy. During pregnancy, women with thrombotic disorders including FVL are often considered candidates for antepartum anticoagulation with low molecular weight heparin. Pregnancy complications related to thrombosis and the unpredictable timing of labor cause unique challenges with regard to the provision of regional anesthesia. A patient with heterozygotic FVL presenting with thrombotic disease and a complicated anticoagulation status lead us to review 16 additional parturients with FVL. This report focuses on the anesthetic implications that arise in parturients with FVL. We recommend that anesthesiologists be made aware of FVL patients before their due date, anticoagulation with low molecular weight heparin should be transitioned to unfractionated heparin before the 38th gestational week, and multidisciplinary collaborative investigation and care should continue for this disorder.

Neonatal respiratory distress syndrome as a function of gestational age and an assay for surfactant-to-albumin ratio

OBJECTIVE

Neonatal respiratory distress syndrome (RDS) affects approximately 1% of live births, and the probability of RDS continues to be a major determinant in the timing of delivery. This study was designed to investigate the optimal gestational age-specific cutoff value for a surfactant-to-albumin ratio assay for predicting RDS.

METHODS

Amniotic fluid surfactant-to-albumin ratio data were collected prospectively for a 2-year period. Women were included in the study if they delivered within 72 hours of surfactant-to-albumin ratio estimation. RDS was defined by the presence of 2 or more of the following criteria: evidence of respiratory compromise shortly after delivery and a persistent oxygen requirement for more than 24 hours, administration of exogenous pulmonary surfactant, and/or radiographic evidence of hyaline membrane disease.

RESULTS

A total of 415 mother-neonate pairs (28 RDS, 387 non-RDS) met criteria for analysis. Both gestational age and surfactant-to-albumin ratio values were independent predictors of RDS. By modeling the odds of RDS by using a logistic regression with gestational age and surfactant-to-albumin ratio values as continuous variables, a probability of RDS of 15% or less can be achieved with a surfactant-to-albumin ratio cutoff of 60 mg or more surfactant/g albumin at 28 weeks of gestation, 50 or more at 30 weeks, 40 or more at 33 weeks, 30 or more at 35 weeks, and 20 or more at 37 weeks.

CONCLUSIONS

These data describe a means of stratifying the probability of neonatal RDS using both gestational age and surfactant-to-albumin ratio value and may be a useful model for clinical decision-making.

LEVEL OF EVIDENCE

II-2

Prolonged latency after preterm premature rupture of membranes: an evaluation of histologic condition and intracranial ultrasonic abnormality in the neonate born at <28 weeks of gestation

OBJECTIVE

The purpose of this study was to evaluate whether infants who were delivered at <28 weeks of gestation after prolonged latency in pregnancies that were complicated by preterm premature rupture of membranes are at increased risk of histologic chorioamnionitis and intracranial ultrasound abnormalities.

STUDY DESIGN

A retrospective cohort analysis of 430 singleton infants born at <28 weeks of gestation in five hospitals (January 1991 through December 1993) with at least one of three protocol cranial scans read by a consensus committee and with placental pathologic evidence. Outcome variables were placental (histologic chorioamnionitis, fetal vasculitis) and neonatal (intraventricular hemorrhage, echolucencies, ventriculomegaly). Latency was divided into five intervals, and outcomes in the longer four intervals were compared with those in infants who were delivered at <1 hour after membrane rupture. Each outcome-latency relationship was evaluated in a logistic model that was controlled for confounders.

RESULTS

Odds ratios and CIs for each latency interval that was controlled for confounders that included gestational age, maternal race, antenatal steroid and antibiotic administration, and delivery mode show a statistically significant increase in the risk of histologic chorioamnionitis and fetal vasculitis. Models for intraventricular hemorrhage, ventriculomegaly, and echolucencies failed to demonstrate significant differences with increasing latency.

CONCLUSIONS

Ascending transcervical infection after preterm premature rupture of membranes is documented by the increasing odds ratios of placental inflammation. The odds of ultrasonically detectable brain abnormalities, however, did not increase with increasing latency.

Perinatal outcome after preterm premature rupture of membranes with in situ cervical cerclage

OBJECTIVE

The presence of a cervical cerclage at the time of preterm premature rupture of membranes (pPROM) could promote clinically evident infection and adverse pregnancy outcome. This cohort study examines whether the presence of cerclage at the time of pPROM is associated with increased maternal or neonatal inflammatory morbidity.

STUDY DESIGN

All singleton pregnancies with cerclage and pPROM between 24.0 and 33.9 weeks' gestation at our institution (January 1985-December 1997) were reviewed. Controls (pPROM without cerclage) were matched 2.5:1 by year of presentation. Outcome measures suggest clinical evidence of an infectious response and include maternal admission white blood cell count, time to onset of preterm labor, clinical chorioamnionitis, postpartum fever, neonatal white-matter disease (intraventricular hemorrhage or periventricular leukomalacia) at less than 33 weeks, neonatal sepsis, and neonatal death.

RESULTS

One hundred fourteen cases of pPROM and cerclage were matched with 288 controls. The study had power (alpha =.05, power = 0.8) to detect a two-fold difference in incidence of adverse neonatal outcome. Among the mothers, the incidence of clinical chorioamnionitis (14.0% vs 18.8%, P =.26), uterine activity at admission (33.3% vs 32.2%, P =.44), maternal postpartum fever (7.9% vs 7.6%, P =.93) in cerclage versus no cerclage were equivalent. Among the neonates, the incidence of neonatal white- matter disease (15.3% vs 13.7%, P =.75), neonatal sepsis (9.1% vs 6.0%, P =.21), and neonatal death were similar.

CONCLUSION

Rates of maternal and neonatal morbidity were similar between both groups. The close overall similarity between the groups strongly suggest clinically insignificant differences between the two groups. These data indicate that a cervical cerclage at the time of pPROM less than 34 weeks does not adversely affect pregnancy outcome.

Contemporary trends in the management of delivery at 23 weeks' gestation

The objective of this study is to investigate the current understanding of neonatal survival and the willingness to provide aggressive obstetric intervention at the limit of fetal viability among practicing perinatologists in the United States. A pretested survey was mailed to members of the Society for Maternal Fetal Medicine. The survey identified the practitioner's opinion of the lowest limit of viability and gestational ages at which antenatal steroids and cesarean section would first be provided. We also attempted to identify practitioner knowledge of survival at 23 and 24 weeks' gestation and years of perinatal practice. Of the 1244 surveys mailed to members of the Society for Maternal-Fetal Medicine practicing in the United States, 462 practitioners replied for a 37% response rate. Fifty percent considered the lower limit of viability to be 24 weeks' and 44.3% believed the lower limit of viability to be 23 weeks' gestation. Among respondents, the majority estimated a 0 to 10% survival rate at 23 weeks' and 25 to 50% survival rate at 24 weeks. Only 13% of respondents correctly estimates survival at 23 weeks' gestation as >25%, and only 17% correctly estimated survival at 24 weeks' at >50%. Among practitioners, 43.6% would first give antenatal steroids after 24 weeks' gestation but 55.6%would administer steroids before the beginning of week 24. Twenty-eight percent would routinely monitor a fetus less than 24 weeks' gestation. Consistent with this observation, 21% would perform a cesarean section before 24 weeks' gestation. We find that respondents underestimate the consensus in the most recent literature on survival of infants born at 23 to 24 weeks. This underestimation may lead to a limitation in interventions offered.

Prenatal ultrasonography and the diagnosis of fetal cleft lip

OBJECTIVE

To determine the efficacy of obstetric ultrasonography in the detection of fetal cleft lip.

METHODS

The study population included all women who had a fetal anatomic survey with adequate visualization of the face and who gave birth at Brigham and Women's Hospital between January 1, 1990, and January 31, 2000. All neonates born with cleft lip were identified from the Brigham and Women's Active Malformation Surveillance Program. Confirmation of the anatomic defect was obtained from the pediatric record or from the pathologic report if the pregnancy was terminated or ended in miscarriage. Cases of isolated cleft palate were excluded. An ultrasonography database was used to identify all cases of cleft lip diagnosed before delivery. Maternal information regarding the pregnancy was abstracted from the medical record. Statistical significance was determined using the chi2 statistic for categorical variables and the t test for continuous variables.

RESULTS

A total of 56 confirmed cases of cleft lip were identified in the study population. Overall, 73% of the cases (41 of 56) were identified antenatally. Additional fetal anomalies were present in 54% of the cases (30 of 56). A comparison between those cases that were detected and those in which the diagnosis was missed showed that there was a significantly lower detection rate if the ultrasonography was performed before 20 weeks (12 [57%] of 21 versus 29 [83%] of 35; P = .035). There was no difference between the 2 groups in terms of maternal age or weight. Maternal parity, prior maternal abdominal surgery, the presence of a multiple gestation, or coexisting fetal anomalies did not significantly affect the detection rate. There was no difference in detection rate in the first half of the study period (1990-1995; 23 [72%] of 32) compared with the second half (1996-2000; 18 [76%] of 24; P = .79).

CONCLUSIONS

In this cohort of women, the rate of detection of fetal cleft lip was significantly lower when the anatomic survey was performed before 20 weeks' gestation. This difference could not be accounted for by such variables as prior maternal abdominal surgery, coexisting fetal anomalies, or improvements in ultrasonographic detection with time. We recommend that the anatomic survey for fetuses at high risk for this condition be performed after 20 weeks' gestation.

Neonatal outcome of infants born at 23 weeks' gestation

OBJECTIVE

To determine the neonatal outcome in accurately dated 23-week deliveries.

METHODS

We reviewed the records of consecutive births between 23 0/7 and 23 6/7 weeks at Brigham & Women's Hospital, Boston, Massachusetts, from January 1995 to December 1999. Women were excluded if they presented for elective termination or had known fetal death or poor dating criteria. Neonatal records were abstracted for mortality and short-term morbidity, including the respiratory distress syndrome (RDS), intraventricular hemorrhage, chronic lung disease, necrotizing enterocolitis, periventricular leukomalacia, and retinopathy of prematurity. Survival was defined as discharge from neonatal intensive care.

RESULTS

Thirty-three singleton pregnancies met criteria for inclusion, 11 of whom survived to discharge (survival rate 0.33; 95% CI 0.18, 0.52). More advanced gestational age was associated with increased likelihood of survival: 0 of 12 at 23 0/7 to 23 2/7 weeks, 4 of 10 at 23 3/7 to 23 4/7 weeks, and 7 of 11 at 23 5/7 to 23 6/7 weeks (P =.02). All 11 survivors developed RDS and chronic lung disease. One of 11 survivors had necrotizing enterocolitis, and 2 of 11 had severe retinopathy of prematurity. One survivor had periventricular leukomalacia on head ultrasonography, compared with 7 of the nonsurvivors who had head ultrasonography (P =.03). One survivor developed severe intraventricular hemorrhage (grade 3 or 4) compared with 8 of the 12 at-risk nonsurvivors who had head ultrasonography (P =.01).

CONCLUSION

About one third of infants delivered at 23 weeks' gestation survived to be discharged from neonatal intensive care. More advanced gestational age was associated with increased likelihood of survival. No neonates survived free of substantial morbidity.

Management of cervical cerclage and preterm premature rupture of the membranes: should the stitch be removed?

OBJECTIVE

Our aim was to determine whether retention of cerclage after preterm premature rupture of the membranes occurring before 34 completed weeks' gestation influences pregnancy outcome.

STUDY DESIGN

Singleton pregnancies with cerclage and premature rupture of the membranes between 24.0 and 34.9 weeks were reviewed. Women were excluded if they were first seen in labor, had chorioamnionitis, or were delivered within 48 hours. Control subjects consisted of women with premature rupture of the membranes without cerclage.

RESULTS

Eighty-one cases of cerclage with premature rupture of the membranes met criteria for inclusion: 30 women (37%) had their cerclage removed at presentation, and 51 (63%) retained the cerclage until delivery. Cases were similar in terms of gestational age at placement and gestational age at premature rupture of the membranes. There was no significant difference between the retained, removed, or control groups in terms of latency, gestational age at delivery, chorioamnionitis, or neonatal morbidity and mortality.

CONCLUSIONS

Retention of cervical cerclage after premature rupture of the membranes occurring before 34 completed weeks' gestation is associated with comparable clinical outcomes with respect to latency and perinatal outcome, when compared with removal of the cerclage.

Nutrition in adolescent pregnancy

Prevention of unintended adolescent pregnancy is a primary goal of the American Academy of Pediatrics and of many health providers. Nevertheless, many adolescents become pregnant every year in America. Pediatricians therefore should be aware of nutritional recommendations for pregnant adolescents to provide optimal care. The importance of nutrition during pregnancy is here reviewed from a pediatric perspective. Pregnancy, particularly during adolescence, is a time of extreme nutritional risk. The adolescents most likely to become pregnant are often those with inadequate nutritional status and unfavorable socio-economic background. There is increasing evidence of competition for nutrients between the growing pregnant adolescent and her fetus. Also, the prenatal environment has been implicated in the development of obesity, cardiovascular disease, and diabetes in both the mother and her offspring. Many adolescents have poor diet quality and poor knowledge of appropriate nutrition; these habits may not change during pregnancy. Current knowledge and recommendations regarding the intake of energy, calcium, and folate are discussed in detail.

Differences in TDx fetal lung maturity assay values between twin and singleton gestations

OBJECTIVE

The purpose of this study was to quantify differences in indexes of pulmonary maturity between singleton and twin gestations by means of the TDx fetal lung maturity assay.

STUDY DESIGN

We identified records of a total of 830 singleton and twin pregnancies not complicated by diabetes and delivered between 28 and 37 weeks' gestation from December 1994 through August 1995. Among these, 170 (20%) had TDx fetal lung maturity measurements performed within 72 hours of delivery. Linear regression was used to assess differences in TDx fetal lung maturity assay values between singleton gestations (n = 143 gestations) and twin gestations (n = 27 gestations) while controlling for potential confounding factors.

RESULTS

Twin gestations were no more likely than singleton gestations to undergo TDx fetal lung maturity screening (odds ratio, 1.3; 95% confidence interval, 0.8-2.2). Pregnancy complications and corticosteroid treatment were similar in the two groups. After 31 weeks' gestation the twin gestations had significantly higher TDx fetal lung maturity values. Linear regression with controls for gestational age indicated that twin gestations on average had a TDx fetal lung maturity value that was 22.0 mg/g (95% confidence interval, 9.8-34.6 mg/g) higher than that of gestational age-matched singleton gestations.

CONCLUSION

Beyond 31 weeks' gestation twin pregnancies appeared to have a TDx fetal lung maturity value that was 22 mg/g higher than that of singleton pregnancies. If the underlying incidences of respiratory distress syndrome are similar between twin and singleton gestations, then the potential exists for false-positive prediction of adequate lung maturity values among twin gestations.