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PubMed1992

Early prediction of preterm delivery by transvaginal ultrasonography.

The clinical value of transvaginal ultrasonography in the evaluation of the uterine cervix of pregnant women was studied. Comparison with conventional transabdominal ultrasound in 24 pregnant subjects revealed that transvaginal ultrasound was superior, because the transabdominal technique usually requires a full bladder, which causes deformation and elongation of the cervix. Digital examination showed dilatation of the internal os in only ten (38.5%) of 26 patients in whom it had previously been shown by transvaginal sonography. Transvaginal ultrasonography has the advantage of providing natural and objective information on the cervix. The values of three sonographic signs found transvaginally for predicting preterm delivery were evaluated in a total of 130 at-risk patients and 129 control subjects. Shortening of the cervical length by -1.5 SD or more was associated with an increased risk of preterm delivery (11.3% vs. 2.8%, p < 0.01). A dilated internal os of more than 5 mm before 30 weeks of gestation was associated with preterm delivery more often than an undilated internal os (33.3% vs. 3.5%, p < 0.01). Dynamic changes in the degree of dilatation of the cervical canal which were found in nine women were significantly related with preterm delivery (p < 0.05). But, in the at-risk group, only dilatation of the internal os had a predictive value for preterm birth. From these data, dilatation of the internal os on transvaginal ultrasonography was proved to be an early and important predictor of preterm delivery.

Journal Article↗

PubMed2002

Prediction of preterm premature rupture of membranes by transvaginal ultrasound features and risk factors in a high-risk population.

OBJECTIVE: To determine the transvaginal ultrasound features and risk factors that predict preterm delivery (PTD) preceded by either preterm premature rupture of membranes (PPROM) or preterm labor (PTL) in a high-risk population. STUDY DESIGN: Singleton gestations at high-risk for preterm delivery were screened prospectively with transvaginal ultrasound between 14 and 24 weeks. Univariate and multivariate regression analyses were performed for historical obstetric risk factors and transvaginal ultrasound features (cervical length (CL) and cervical funneling (CF)) for the prediction of PTD preceded by PPROM or PTL at < 32 and < 35 weeks' gestation, respectively. Indicated preterm deliveries were excluded. RESULTS: Of 321 patients screened, 71 (22%) delivered at < 35 weeks, 40 (56%) after PPROM and 31 (44%) after PTL. Preterm delivery at < 32 weeks was seen in 47 patients (15%), with 20 (43%) occurring after PTL and 27 (57%) after PPROM. Univariate analysis showed the following to be significant predictors of PPROM at < 35 weeks: a past history of PTD between 25 and 30 weeks (P < 0.008), cerclage in the current pregnancy (P < 0.0001), bacterial vaginosis (P < 0.011), CL < 25 mm (P < 0.0001) and CF > 25% (P < 0.0001). The following were found to be significant predictors of PTL at < 35 weeks: black race (P < 0.02), a cerclage in the current pregnancy (P < 0.01), CL < 25 mm (P < 0.001) and CF > 25% (P < 0.0001). The significant predictors of PPROM at < 32 weeks were cerclage in the current pregnancy (P < 0.006) and CL < 25 mm (P < 0.0001); for PTL at < 32 weeks they were a past history of spontaneous miscarriage between 14 and 24 weeks (P < 0.02), black race (P < 0.021), cerclage in the current pregnancy (P < 0.001) and CL < 25 mm (P < 0.001). Multivariate regression analysis revealed the significant predictors of PPROM at < 35 weeks to be: a history of PTD between 25 and 30 weeks with odds ratio (OR) 4.8 (95% confidence interval (CI), 1.9-11.5) and CL < 25 mm with OR 7.9 (95% CI, 3.6-17.5). The significant predictors of PTL at < 35 weeks on multivariate regression were black race with OR 2.2 (95% CI, 1.0-4.8) and unemployment with OR 1.2 (95% CI, 1.0-1.5). For deliveries < 32 weeks, CL < 25 mm (OR, 10.1; 95% CI, 3.2-32) was the only significant predictor of PPROM. Significant predictors of PTL were unemployment (OR, 1.3; 95% CI, 1.1-1.7), a history of spontaneous miscarriage between 14 and 24 weeks (OR, 6.2; 95% CI, 1.4-25), black race (OR, 8.6; 95% CI, 1.5-47) and CL < 25 mm (OR, 4.4; 95% CI, 1-19). The sensitivity, specificity and positive and negative predictive values of CL < 25 mm for PPROM at < 35 weeks were 73%, 69%, 25% and 95%, respectively; for PTL at < 35 weeks they were 58%, 66%, 15% and 94%; for PPROM at < 32 weeks they were 85%, 68%, 20%, and 98%; for PTL at < 32 weeks they were 70%, 66%, 12% and 97%. CONCLUSION: There are differences in both transvaginal ultrasound findings and risk factors that predict PPROM or PTL. Of the pathways leading to PTD, CL was a more significant predictor of PPROM compared with PTL, while sociodemographic factors were more predictive of PTL.

Adult↗

PubMed2000

Preterm birth and the availability of cord blood for HPC transplantation.

BACKGROUND: Cord blood from deliveries at term can be used for HPC transplantation. The objective of this study was to determine the amounts of cord blood nucleated cells (NCs) and HPCs that were collectable from preterm deliveries. STUDY DESIGN AND METHODS: Cord blood collected from preterm deliveries between 22 and 36 weeks of gestation was compared with regard to volume, NC count (/mL), CD34+ cell count (/mL), and the NC and CD34+ cell counts per cord blood sample and at different gestational ages. RESULTS: A correlation was found between gestational age and NC count (r = 0.52, p<0.001), and an inverse relation was found between gestational age and CD34+ cell count (r = - 0.68, p<0.001). The CD34+ cell count per cord blood sample was independent of gestational age (r = - 0.13, p = NS), and no significant difference between early (22-32 week) and late (33-36 week) preterm deliveries was found (p = 0.870). Comparison with published data from cord blood transplantations revealed that up to one-third of preterm samples contained at least as many NCs (or CD34+ cells) as the median cell dose transplanted (calculated for the median recipient weight) in the respective study. Furthermore, 77 percent of all preterm samples contained at least 1 x 10(7) NCs (and 42% at least 1 x 10(5) CD34+ cells) per kg for transplantation in a recipient of 20-kg body weight, which corresponds to the lower threshold of cells per kg in the graft recommended by Eurocord. CONCLUSION: Preterm delivery should not be a reason to exclude cord blood collection if allogeneic cord blood transplantation in a sibling is planned.

Blood Donors↗

PubMed2006

Risk factors for neonatal morbidity and mortality among "healthy," late preterm newborns.

Research about neonatal outcomes among late preterm infants (34 weeks through 36 6/7 weeks of gestation) is limited. Understanding which late preterm infants are at risk for neonatal morbidity or mortality is necessary to improve health outcomes and reduce hospital costs. We conducted a population-based cohort study of "healthy," singleton late preterm infants vaginally delivered in Massachusetts hospitals to Massachusetts residents between 1998 and 2002. We compared the incidence of neonatal morbidity (postdelivery inpatient readmissions, observational stays, or mortality) between "healthy," late preterm infants with and without infant, obstetric, and sociodemographic factors by calculating risk ratios adjusted for confounding. Of the 9552 late preterm, "healthy" infants, 4.8% had an inpatient readmission and 1.3% had an observational stay. Infants with neonatal morbidity were more likely to be firstborn, be breastfed at discharge, have labor and delivery complications, be a recipient of a public payer source at delivery, or have an Asian/Pacific Islander mother. Non-Hispanic blacks had a decreased risk for neonatal morbidity compared to other racial/ethnic groups. Knowledge of risk factors for neonatal morbidity among "healthy" late preterm infants can be used to identify infants needing closer monitoring and earlier follow-up after hospital discharge.

Adolescent↗

PubMed2006

Multiple gestations and late preterm (near-term) deliveries.

Multiple gestations present unique challenges to the modern obstetrician. Many twin and high-order multiple pregnancies are delivered between 34 and 37 weeks' gestation either secondary to preterm labor or obstetrical complications necessitating intervention. Recognizing the increasing prevalence of multiple gestations and the impact of late preterm deliveries in modern practice, this review analyzes the impact of multiple pregnancies on perinatal outcomes, reviews the strategies to prevent preterm labor, and summarizes potential indications for late preterm delivery. In this paper, "late preterm" has been used instead of "near-term," as the former was considered more appropriate to reflect this subgroup of preterm infants in a workshop on this topic held in July 2005, organized by the National Institute of Child Health and Human Development.

Female↗

PubMedDate not supplied

Polymorphonuclear leukocytes in the fetal membranes are activated in patients with preterm delivery: ultrastructural and enzyme-histochemical evidence.

The purpose of this study was to examine evidence for the presence of activated leukocytes in the fetal membranes from patients with preterm delivery. Polymorphonuclear leukocytes in fetal membranes from seven patients with preterm delivery (26-32 weeks of gestation) were analysed using transmission electron microscopy and ultrastructural enzyme-histochemistry for peroxidase and alkaline phosphatase. A large number of leukocytes accumulated in the fetal membranes from preterm deliveries. Phagosome, phagocytosis of cell debris, attachment of primary granules to the phagosomal membrane and cell surface projections were observed in fetal membrane leukocytes from preterm delivery but not in peripheral blood leukocytes. Peroxidase and alkaline phosphatase activity was demonstrated on the plasma membrane of the phagosomes. Morphological and enzyme-histochemical observation indicated that polymorphonuclear leukocytes in the fetal membrane in patients with preterm delivery were stimulated or activated. Such activated leukocytes may play a role in the pathophysiology or pathogenesis of preterm delivery.

Alkaline Phosphatase↗

PubMed2001

A systematic approach to the management of preterm labor.

Preterm birth occurs in 7% to 12% of all deliveries, but accounts for over 85% of all perinatal morbidity and mortality. Although the ability of obstetric care providers to identify women at risk for preterm delivery has improved, the overall incidence of preterm birth has remained unchanged for the past 30 years. Preterm birth remains the single greatest challenge for physician-researchers in the field of maternal-fetal medicine in the 21st century. This article reviews in detail the current state of the literature as regards the etiology, pathophysiology, prevention, and treatment of premature labor and preterm birth. A better understanding of the molecular mechanisms responsible for the process of labor, both at term and preterm, will improve our ability to identify and manage women at risk of premature delivery.

Animals↗

PubMed2007

Genetic influences on preterm birth.

The high prevalence, increasing frequency, and adverse outcomes for mothers and infants of preterm birth have led to heightened awareness of this public health concern. The causes of preterm birth are likely to be multifactorial, with genetic, infectious, nutritional, behavioral, and other environmental contributors. Because of important differences in the physiology of human pregnancy and that of nonprimate mammals, extrapolation of mechanisms from animal model systems to humans has had limited impact on the understanding of human prematurity. This review summarizes work from many groups that implicates important genetic contributions to human preterm birth. These efforts use epidemiological, classical genetic, and more recently, genomic science approaches to determine pregnancies at risk for preterm delivery and to facilitate an understanding of the substantial racial disparity in preterm birth. Data revealing racial and familial predispositions to prematurity, along with genetic polymorphisms conferring increased preterm birth, promise new insights into the understanding and treatment of this critical problem.

Animals↗

PubMed1999

Preterm birth in Sjögren-Larsson syndrome.

Sjögren-Larsson syndrome (SLS) was originally described as a triad of spasticity, mental retardation and congenital ichthyosis. The syndrome reflects an underlying deficiency of microsomal fatty aldehyde dehydrogenase (FALDH). We report on clinical data concerning pregnancy, labor and neonatal period in 15 patients. Pregnancies were uncomplicated, except for preterm rupture of membranes in three pregnancies, and the occurrence of preterm birth. Mean gestational age was 35.3 weeks (S.D. 2.4 weeks), and preterm birth was found in 73% of the children, while all children were born before or in the 38th week of gestation. Birth weight was normal for gestational age in all patients. The neonatal period was free from serious complications, apart from hemolytic disease in two patients. Preterm birth was found in 7% of the healthy siblings, reflecting the normal population. Prematurity and spasticity are intrinsic and concurrent parts of SLS, without causal relation. SLS should be considered in every neonate with congenital ichthyosis, especially if the child is born preterm. A possible explanation for preterm birth in SLS could be the defective inactivation of leukotriene B4 (LTB4), which recently has been demonstrated in patients with SLS.

Aldehyde Dehydrogenase↗

PubMed1995

Markers of infection and their relationship to preterm delivery.

In this study we evaluated different markers of infection and their relationship to preterm delivery. Forty-four consecutive women with singleton pregnancies in uncomplicated preterm labor were investigated. C-reactive protein (CRP) in peripheral maternal blood, amniotic fluid cytokines, amniotic fluid leukocyte count, and amniotic fluid culture were performed in all patients. Thirty-six patients responded to standard tocolytic therapy and delivered after 34 weeks' gestation. In eight patients treatment failed and they delivered before 34 weeks' gestation. Two of these eight patients had a positive amniotic fluid culture for Ureaplasma urealyticum. The positive culture was accompanied by an elevated neutrophil count in the amniotic fluid. Elevated amniotic fluid levels of tumor necrosis factor (TNF) (more than 23 pg/mL), interleukin-6 (IL-6) (more than 2292 pg/mL) and interleukin-8 (more than 164 pg/mL) correlated with early preterm delivery. CRP levels in serum had a low sensitivity (38%) but a high specificity (94%) in predicting preterm delivery. This study indicates that preterm labor can be initiated by infection. Markers of infection obtained by amniocentesis have a better sensitivity and positive predictive value than noninvasive markers. Elevated IL-6 (more than 2292 pg/mL) seems to be the best predictor for preterm delivery, with a sensitivity of 75% and a specificity of 97%.

Amniocentesis↗

PubMed1989

Cervical change and uterine activity as predictors of preterm delivery.

Premature uterine activity and early cervical change have both been shown to be useful in predicting preterm delivery. Prospective studies evaluating weekly uterine activity and cervical change were performed in 20 women, 17 of whom were at risk for preterm delivery, starting at 20 to 25 weeks' gestation. Patients were followed weekly until either 36 weeks' gestation or until the onset of premature labor or delivery. Seven women delivered before 37 weeks' gestation (preterm group). Thirteen women did not require tocolysis and delivered after 37 weeks' gestation (term group). A Bishop score was assessed weekly and the score added to the prior values in order to obtain a cumulative cervical score. A similar process was used to assess uterine activity. The cumulative values of Bishop score and uterine activity were plotted against gestational age in both groups. There was no observed increase in cumulative uterine activity in the preterm group before delivery. However, there was a progressive increase in cumulative cervical change weeks before delivery in the preterm group (p less than 0.05). Despite the small sample size, we conclude that progressive cervical change precedes the onset of labor and may be a better predictor of preterm delivery than is weekly monitoring of uterine activity.

Cervix Uteri↗

PubMed1987

Antibacterial activity of amniotic fluid in the early third trimester. Its association with preterm labor and delivery.

The purpose of this study was to determine the bacterial growth inhibitory property of amniotic fluid (AF) from patients in the early third trimester and to examine its relationship to preterm labor and delivery. A total of 38 AF samples from patients between 27 and 35 weeks gestation with intact membranes were studied. Antibacterial activity was tested against Escherichia coli, Staphylococcus aureus, and Bacteroides fragilis. Fifteen fluids were from patients in preterm labor who delivered near term after successful inhibition of labor. Five of these fluids (33%) were inhibitory to E. coli, five (33%) to S. aureus, and 11 (73%) to B. fragilis. Nine fluids were from patients who failed inhibition of labor and delivered preterm; none of these were inhibitory to E. coli, two (22%) to S. aureus, and only one (11%) to B. fragilis (P less than 0.005). Two of the nine fluids from patients who failed inhibition of labor also yielded fusobacteria. The remaining 14 fluids were obtained from patients without preterm labor and exhibited antibacterial activity similar to that from patients with successful labor inhibition. Results suggest a relationship between the absence of AF antibacterial activity against B. fragilis and preterm delivery in patients with preterm labor and intact membranes.

Amniocentesis↗

PubMed1988

The developmental profile and outcome of 325 unselected preterm infants up to two years of age.

A regional birth cohort of 351 preterm infants born between the 1st June, 1981 and the 31st May, 1982 was followed-up during the first two years of life. The follow-up data were obtained from 325 preterm infants. The term, appropriate-for-gestational age low-risk infants born in the region during the same period served as a control population. The follow-up examinations took place at the well-baby clinics run by public health nurses and health centre physicians at 3, 6, 12, 18 and 24 months of conceptional age. A modification of the Denver Developmental Screening Test was applied in the follow-up. In 15 (5%) preterm infants the developmental outcome at two years was doubtful or abnormal. The developmental outcome at two years was doubtful or abnormal. The developmental outcome in preterm infants was associated with gestational age, birthweight, severity of respiratory distress and five-minute Apgar score when analyzed separately. After stepwise logistic regression analysis only five-minute Apgar score significantly predicted the gross motor and fine motor outcomes while the psychosocial outcome was associated with five-minute Apgar score and birthweight. The developmental profiles of the preterm infants differed from those of the control infants by showing higher percentages of unoptimal scores especially in fine motor development at three months and psychosocial development at two years. The prognosis for preterm infants without complications was, however, near that of their term peers.

Animals↗

PubMed1990

Does very preterm birth impair myelination of the central nervous system?

Myelination of the central nervous system (CNS) can be demonstrated with magnetic resonance (MR) imaging. Myelin formation may be reduced in conditions of neonatal "undernutrition". Very preterm infants have a reduced postnatal growth rate when compared with intrauterine fetuses of the same gestational age. Using MR imaging, we studied qualitative myelination patterns in healthy preterm infants of less than 30 weeks gestation with an optimal nutritional intake and in term infants at 44 weeks postmenstrual age (PMA). At that age, preterm infants had a significantly lower mean body weight than term infants, but mean head circumference did not differ significantly. All preterm and term infants had reached myelination stage M3 (myelin in brainstem, internal capsule, and corona radiata) and M4 (myelin in brainstem, internal capsule, corona radiata, and centrum semiovale). There was no significant difference in myelination stage between the preterm and term infants. We conclude that adequate nutrition in the neonatal period leads to qualitatively adequate myelination of the CNS in very preterm infants.

Central Nervous System↗

PubMed1995

Association between bacterial vaginosis and preterm delivery of a low-birth-weight infant. The Vaginal Infections and Prematurity Study Group.

BACKGROUND: Bacterial vaginosis is believed to be a risk factor for preterm delivery. We undertook a study of the association between bacterial vaginosis and the preterm delivery of infants with low birth weight after accounting for other known risk factors. METHODS: In this cohort study, we enrolled 10,397 pregnant women from seven medical centers who had no known medical risk factors for preterm delivery. At 23 to 26 weeks' gestation, bacterial vaginosis was determined to be present or absent on the basis of the vaginal pH and the results of Gram's staining. The principal outcome variable was the delivery at less than 37 weeks' gestation of an infant with a birth weight below 2500 g. RESULTS: Bacterial vaginosis was detected in 16 percent of the 10,397 women. The women with bacterial vaginosis were more likely to be unmarried, to be black, to have low incomes, and to have previously delivered low-birth-weight infants. In a multivariate analysis, the presence of bacterial vaginosis was related to preterm delivery of a low-birth-weight infant (odds ratio, 1.4; 95 percent confidence interval, 1.1 to 1.8). Other risk factors that were significantly associated with such a delivery in this population were the previous delivery of a low-birth-weight infant (odds ratio, 6.2; 95 percent confidence interval, 4.6 to 8.4), the loss of an earlier pregnancy (odds ratio, 1.7; 1.3 to 2.2), primigravidity (odds ratio, 1.6; 1.1 to 1.9), smoking (odds ratio, 1.4; 1.1 to 1.7); and black race (odds ratio, 1.4; 1.1 to 1.7). Among women with bacterial vaginosis, the highest risk of preterm delivery of a low-birth-weight infant was found among those with both vaginal bacteroides and Mycoplasma hominis (odds ratio, 2.1; 95 percent confidence interval, 1.5 to 3.0). CONCLUSIONS: Bacterial vaginosis was associated with the preterm delivery of low-birth-weight infants independently of other recognized risk factors.

Cohort Studies↗

PubMed1998

Monitoring women at risk for preterm labor.

BACKGROUND: Preterm birth is a major cause of perinatal morbidity and mortality. Whether the rate of preterm birth can be reduced by frequent contact between nurses and pregnant women or home monitoring of uterine activity is not known. METHODS: We randomly assigned 2422 pregnant women with known risk factors for preterm labor (including 844 women who were pregnant with twins) to receive education and to have one of the following: weekly contact with a nurse, daily contact with a nurse, or daily contact with a nurse and home monitoring of uterine activity. The nurses elicited the women's own assessments of their symptoms and signs of preterm labor. The primary end point was the incidence of birth at less than 35 weeks' gestation. Secondary end points included cervical status at the time preterm labor was diagnosed and birth weight. RESULTS: There were no significant differences among the groups in the incidence of birth at less than 35 weeks (14 percent in the weekly-contact group, 13 percent in the daily-contact group, and 14 percent in the home-monitoring group), in the mean amount of cervical dilatation at the time preterm labor was diagnosed (1.8 cm, 1.5 cm, and 1.4 cm, respectively), or in such neonatal outcomes as birth weights of less than 1500 g or less than 2500 g. However, daily contact with a nurse increased the mean number of unscheduled visits to obstetricians (1.2 in the weekly-contact group, 1.8 in the daily-contact group, and 2.3 in the home-monitoring group) and the proportion of women who received prophylactic tocolytic drugs (12 percent, 14 percent, and 19 percent, respectively). CONCLUSIONS: Women who have daily contact with a nurse, with or without home monitoring of uterine activity, have no better pregnancy outcomes than women who have weekly contact with a nurse.

Adult↗

PubMed2002

Frequency of uterine contractions and the risk of spontaneous preterm delivery.

BACKGROUND: The measurement of the frequency of uterine contractions has not been useful for reducing the rate of preterm delivery in randomized trials. Nonetheless, ambulatory monitoring of contractions continues to be used in clinical practice. METHODS: We assessed the frequency of uterine contractions as a predictor of the risk of spontaneous preterm delivery before 35 weeks of gestation. We enrolled women with singleton pregnancies between 22 and 24 weeks of gestation. The women used a contraction monitor at home to record contraction frequency twice daily on 2 or more days per week from enrollment to delivery or 37 weeks of gestation. RESULTS: We obtained 34,908 hours of successful monitoring recordings from 306 women. Although more contractions were recorded from women who delivered before 35 weeks than from women who delivered at 35 weeks or later, we could identify no threshold frequency that effectively identified women who delivered preterm infants. The sensitivity and positive predictive value of a maximal hourly frequency of contractions of four or more between 4 p.m. and 3:59 a.m. were 9 percent and 25 percent, respectively, at 22 to 24 weeks and 28 percent and 23 percent at 27 to 28 weeks. Other proposed screening tests, such as digital and ultrasound evaluations of the cervix and assays for fetal fibronectin in cervicovaginal secretions, also had low sensitivity and positive predictive value for preterm labor. CONCLUSIONS: Although the likelihood of preterm delivery increases with an increased frequency of uterine contractions, measurement of this frequency is not clinically useful for predicting preterm delivery.

Cervix Uteri↗

PubMed2000

Twin birth weight discordance and risk of preterm birth.

OBJECTIVES: Our purpose was to determine whether birth weight discordance is a risk factor for preterm birth of twins, and to further characterize the relationships involved. STUDY DESIGN: Maternally linked 1978-1990 Missouri birth certificates were used to analyze gestations resulting in live twins. We used contingency tables and multiple logistic regression. RESULTS: The degree of discordance correlated strongly with risk for live preterm birth but only for discordances >30% and preterm birth at <32 weeks' gestation. Among 9479 pregnancies with discordance <30%, 9.5% ended in birth at <32 weeks' gestation, versus 13.7% of 326 with discordance of 30% to 40% (P =.03) and versus 34.1% of 126 with discordance > or =40% (P <. 001). There were 42 preterm twin births at <32 weeks' gestation with discordances > or =40%. Of these, 51% were attributable to fetal growth restriction and 16% to large size for gestational age in one infant; in 72% the smaller twin was the second born, and in 86% the twins were like sex. The relative association between > or =40% discordance and preterm birth at <32 weeks' gestation was strengthened (final odds ratio, 9.54; P <.0001) in a multivariate model containing other risk factors for delivery at <32 weeks' gestation: black race, either twin small for gestational age, unmarried, teenage mother, number of male fetuses, like fetal sex, education <12 years, nulliparity, and cigarette smoking. CONCLUSIONS: Twin birth weight discordance has now clearly been demonstrated to be a risk factor for preterm birth. The effect was found particularly with discordances > or =40% before 32 weeks' gestation. Discordance was usually attributable to fetal growth restriction, most often in the second-born twin.

Birth Order↗