Cervical length in uncomplicated pregnancy: A study of sociodemographic predictors of cervical changes across gestation

Vaginal progesterone for prevention of preterm birth in women with a history of preterm birth regardless of cervical length: an argument for use

It is well understood that preterm birth accounts for a substantial amount of poor neonatal outcomes. In 2022, preterm birth affected about 1 of every 10 infants born in the United States with complications ranging from mild respiratory distress syndrome to neonatal death. The complexity of the treatment is secondary to the fact that preterm birth is a multifactorial syndrome with intricate sociocultural factors that influence our racially disproportionate poor outcomes. One of the key risk factors for preterm birth is a history of spontaneous preterm birth. Currently, there are conflicting recommendations regarding the use of vaginal progesterone prophylactically for the prevention of recurrent preterm birth. As described in Practice Bulletin number 234 of the American College of Obstetricians and Gynecologists, the current recommendation is that patients with a singleton pregnancy and previous spontaneous preterm birth should be assessed with serial endovaginal ultrasound cervical length measurements to determine eligibility for vaginal progesterone. In contrast, the Society for Maternal-Fetal Medicine suggests the use of prophylactic vaginal progesterone with patient-centered counseling and shared decision-making. We aimed to present the rationale for the use of prophylactic vaginal progesterone in patients with singleton gestations and a history of spontaneous preterm birth.

Study protocol to quantify the genetic architecture of sonographic cervical length and its relationship to spontaneous preterm birth

INTRODUCTION

A short cervix (cervical length <25 mm) in the midtrimester (18-24 weeks) of pregnancy is a powerful predictor of spontaneous preterm delivery. Although the biological mechanisms of cervical change during pregnancy have been the subject of extensive investigation, little is known about whether genes influence the length of the cervix, or the extent to which genetic factors contribute to premature cervical shortening. Defining the genetic architecture of cervical length is foundational to understanding the aetiology of a short cervix and its contribution to an increased risk of spontaneous preterm delivery.

METHODS/ANALYSIS

The proposed study is designed to characterise the genetic architecture of cervical length and its genetic relationship to gestational age at delivery in a large cohort of Black/African American women, who are at an increased risk of developing a short cervix and delivering preterm. Repeated measurements of cervical length will be modelled as a longitudinal growth curve, with parameters estimating the initial length of the cervix at the beginning of pregnancy, and its rate of change over time. Genome-wide complex trait analysis methods will be used to estimate the heritability of cervical length growth parameters and their bivariate genetic correlation with gestational age at delivery. Polygenic risk profiling will assess maternal genetic risk for developing a short cervix and subsequently delivering preterm and evaluate the role of cervical length in mediating the relationship between maternal genetic variation and gestational age at delivery.

ETHICS/DISSEMINATION

The proposed analyses will be conducted using deidentified data from participants in an IRB-approved study of longitudinal cervical length who provided blood samples and written informed consent for their use in future genetic research. These analyses are preregistered with the Center for Open Science using the AsPredicted format and the results and genomic summary statistics will be published in a peer-reviewed journal.

Development and external validation of a nomogram for predicting preterm birth at < 32 weeks in twin pregnancy

The purpose of this study was to develop a dynamic model to predict the risk of spontaneous preterm birth at < 32 weeks in twin pregnancy. A retrospective clinical study of consecutively asymptomatic women with twin pregnancies from January 2017 to December 2019 in two tertiary medical centres was performed. Data from one centre were used to construct the model, and data from the other were used to evaluate the model. Data on maternal demographic characteristics, transvaginal cervical length and funnelling during 20-24 weeks were extracted. The prediction model was constructed with independent variables determined by multivariate logistic regression analyses. After applying specified exclusion criteria, an algorithm with maternal and biophysical factors was developed based on 88 twin pregnancies with a preterm birth < 32 weeks and 639 twin pregnancies with a delivery ≥ 32 weeks. It was then evaluated among 34 pregnancies with a preterm birth < 32 weeks and 252 pregnancies with a delivery ≥ 32 weeks in a second tertiary centre without specific training. The model reached a sensitivity of 80.00%, specificity of 88.17%, positive predictive value of 50.33% and negative predictive value of 96.71%; ROC characteristics proved that the model was superior to any single parameter with an AUC of 0.848 (all P < 0.005). We developed and validated a dynamic nomogram model to predict the individual probability of early preterm birth to better represent the complex aetiology of twin pregnancies and hopefully improve the prediction and indication of interventions.

The first-trimester of pregnancy - A window of opportunity for prediction and prevention of pregnancy complications and future life

The International Federation of Gynecology and Obstetrics (FIGO) has identified non communicable maternal diseases (NCDs) as a new focus area. NCDs and exposures as related to pregnancy complications and later impairment of maternal and offspring health will form the basis for action in the forthcoming years. This paper summarizes recent advances, centered on the use of first-trimester testing, as a window of opportunity to predict and prevent many pregnancy complications; and for potential future prevention of NCDs in mother and offspring. Recent results from a large-scale randomized control trial have provided definitive proof that effective screening for preterm preeclampsia (preterm-PE), requiring delivery before 37 weeks' gestation, can be achieved with a combined test of maternal factors and biomarkers at 11-13 weeks and that aspirin, given to high-risk women, is effective in reducing the risk of preterm-PE and the length of stay in neonatal intensive care unit. This is the first successful example to illustrate that pregnancy complications is predictable and preventable in early pregnancy. Similar prediction and prevention strategies are being developed for hyperglycemia in pregnancy and preterm birth, with the intention for longer lasting interventions leading to significant downstream impact in improving long-term health in both mothers and babies.

Cervical pathways for racial disparities in preterm births: the Preterm Prediction Study

Purpose: Racial disparities in preterm birth have been long recognized, but the social and biological mechanisms for these differences are unclear. Our analysis had three goals: (1) to determine the relation between race and other social risk factors and cervical structure; (2) to determine whether social factors mediate the relation between race and cervical structure; and (3) to determine whether racial disparities in preterm birth (PTB) are mediated through changes in cervical structure observed earlier in pregnancy. Materials and methods: Data from the Maternal Fetal Medicine Unit network Preterm Prediction Study were used to examine the relation between race and other social factors and cervical properties throughout pregnancy in 2920 black and white women. Outcomes included cervical length and dilation; cervical score (cervical length-internal dilation); and whether membranes protruded at 22-24 and 26-29 weeks. Race, education, income, insurance type, and marital status were examined as predictors of the outcomes using linear and logistic regression, adjusting for age, BMI, parity, and smoking. Mediation analysis was used to examine whether (a) any social factors explained racial differences in cervical properties, and (b) whether cervical properties mediated racial differences in risk for preterm birth. Results: Shorter cervical length, especially at a subject's first visit, was associated with black race (adjusted beta -1.56 mm, p < .01) and lower income (adjusted beta -1.48, p =.05). External dilation was not associated with social factors, while internal dilation was associated with black race and lower education. Black race and marital status were associated with lower cervical score. There was no evidence of mediation of the racial effect on cervical properties by any social factor. Shorter cervical length, dilation, and score were all associated with preterm birth (p < .01). Mediation analysis indicated that each of these mediated the effect of race, but explained a small proportion of the total effect (15-25%). Conclusions: Race, and, to a lesser extent, other social factors are correlated with adverse cervical properties. This pathway could explain a proportion of the racial disparity in preterm birth.

Racial residential segregation and adverse birth outcomes: A systematic review and meta-analysis

RATIONALE

Persistent racial disparities in adverse birth outcomes are not fully explained by individual-level risk factors. Racial residential segregation-degree to which two or more groups live apart from one another-may contribute to the etiology of these birth outcome disparities. Our aim was to assess associations between segregation and adverse birth outcomes by race. This review focused on formal measures of segregation, using Massey and Denton's framework (1998) that identifies five distinct operationalizations of segregation, in addition to proxy measures of segregation such as racial composition, in order to gain a deeper understanding of the operationalizations of segregation most salient for birth outcomes.

METHOD

Review and meta-analyses were conducted using PubMed, PsycINFO and Web of Science and included articles from inception through April 30, 2017.

RESULTS

Forty-two articles examined associations between segregation and adverse birth outcomes among Black and White mothers separately. Meta-analyses showed that among Black mothers, exposure was associated with increased risk of preterm birth (OR = 1.17, 95% CI = 1.10, 1.26), and low birth weight (OR = 1.13, 95% CI=1.06, 1.21), and Black racial composition was associated with increased risk of preterm birth (OR = 1.20, 95% CI=1.05, 1.37), among those living in most- compared to least-segregated neighborhoods. Few studies were conducted among White mothers and only exposure was associated with increased risk of preterm birth and low birth weight. Qualitative analyses indicated that among Black mothers, exposure and hypersegregation were associated with multiple adverse birth outcomes; findings were mixed for evenness and clustering.

CONCLUSIONS AND FUTURE DIRECTIONS

Associations between segregation and adverse birth outcomes differ by race. Methodological heterogeneity between studies may obscure true associations. Research can be advanced through use of multilevel frameworks and by examining mechanistic pathways between segregation and adverse birth outcomes. Elucidation of pathways may provide opportunities to intervene to reduce seemingly intractable racial disparities in adverse birth outcomes.

Racial and social predictors of longitudinal cervical measures: the Cervical Ultrasound Study

OBJECTIVE

To evaluate whether the racial and socioeconomic disparities are present in adverse cervical parameters, and, if so, when such disparities develop.

STUDY DESIGN

A prospective cohort study was conducted. 175 women with a prior preterm birth had up to four endovaginal ultrasounds between gestational weeks 16 and 24 (Cervical Ultrasound Trial of the MFMU). Each sociodemographic factor (race/ethnicity, marital status, insurance funding and education) was examined as a predictor of short cervix or U/funnel shape, using multiple logistic and linear regression. Changes in the cervical length and shape across pregnancy and after pressure were also examined.

RESULTS

The strongest associations were seen between race and government-funded insurance and short cervix and U shape per funneling (race and length <25 mm per funnel: adjusted odds ratio (OR) 5.52, 2.24 to 13.63; government-funded insurance and length <30 mm per funnel: adjusted OR 3.10, 1.34 to 7.15). Changes in cervical length were not associated with sociodemographics.

CONCLUSION

African-American race and, to a lesser extent, insurance funder, are associated with cervical length and shapes that have been associated with preterm birth, and those properties are present largely early in pregnancy.

Racial disparities in cervical length for prediction of preterm birth in a low risk population

PURPOSE

Racial minorities experience higher rates of spontaneous preterm birth (sPTB). Our objective was to evaluate whether there are racial discrepancies in the incidence of second trimester short cervical length (≤25 mm).

MATERIALS AND METHODS

Retrospective cohort of women with singleton gestations without prior sPTB undergoing universal second trimester transvaginal ultrasound cervical length (CL) screening between January 2012 and December 2013. Black women were compared to non-Hispanic white women. Our primary outcome was the incidence of CL ≤25 mm. Secondary outcomes were incidence of PTB ≤37 weeks, delivery mode, birth weight and neonatal intensive care unit (NICU) admission.

RESULTS

Black women (n = 1092) differed from non-Hispanic white women (n = 659) with respect to maternal age (26.0 versus 30.7 years), gravidity (3.1 versus 2.1), prepregnancy BMI (29.6 versus 25.0 kg/m²), and smoking status (9.8% versus 16%), respectively (p < 0.001). Black women had higher incidence of CL ≤25 mm (1.9% versus 0.6%; OR: 3.21 [1.1-9.4]), rates of sPTB (8.5% versus 4.4%; aOR: 1.95 [1.1-3.4]), incidence of low birthweight infants (<2500 g, 8.3% versus 5.6%; aOR 1.80 [1.1-3.0]) and were more likely to have their infants admitted to the NICU (16% versus 11%; OR: 1.52 [1.0-2.3]).

CONCLUSIONS

Black women had a 2.8-fold increased risk of CL ≤25 mm compared non-Hispanic white women in a low-risk population.

Is there a role for cervical assessment and uterine artery Doppler in the first trimester of pregnancy as a screening test for spontaneous preterm delivery?

OBJECTIVE

To evaluate the role of cervical length (CL) and uterine artery pulsatility index (UtA-PI) at 11+0 to 13+6 weeks as predictors of spontaneous preterm delivery (sPTD) in a Chilean population.

METHODS

This was a prospective study of asymptomatic women with singleton pregnancies attending for a nuchal translucency scan at 11+0 to 13+6 weeks' gestation and who underwent a transvaginal scan for evaluation of CL and UtA-PI. Exclusion criteria were fetal and pregnancy complications (other than sPTD) and iatrogenic delivery at<34 weeks. Measurements of CL and UtA-PI were adjusted for fetal crown-rump length and maternal characteristics and expressed as multiples of the median (MoM) of the unaffected group. Prediction of sPTD using maternal and pregnancy characteristics was studied using logistic regression analysis.

RESULTS

A total of 3480 women were recruited into the study and, after application of exclusion criteria, 3310 were included in the analysis. The rate of sPTD at<34 weeks was 0.9% (n=31). A previous PTD had occurred in 7.4% of parous women. Patients with sPTD in the index pregnancy were characterized by a significantly higher prevalence of previous PTD (12.9% vs 3.7%, P<0.05). No significant difference was found in either CL or UtA-PI between pregnancies with and without subsequent sPTD. Logistic regression analysis showed that smoking and previous PTD were significantly associated with sPTD at<34 weeks. The combination of these characteristics provided a detection rate of 26% with a false-positive rate of 8%.

CONCLUSIONS

Neither UtA-PI nor CL during the first trimester was shown to be a useful predictor of early sPTD. However, a combined model that includes smoking and previous PTD predicts approximately one-quarter of those women destined to deliver at<34 weeks, with a false-positive rate of 8%.

Can maternal height predict shorter cervical length in asymptomatic low-risk pregnant women?

OBJECTIVE

To evaluate the association between maternal height and cervical length in the first and second trimesters in low-risk asymptomatic pregnant women.

STUDY DESIGN

Maternal height and cervical length of 146 asymptomatic women with singleton pregnancies at low risk for preterm birth were measured during the first and second trimesters. Preterm birth was defined as birth before <37 gestational weeks. Correlations between maternal height and cervical length measurements were determined using Pearson correlation analysis. The women were also divided into three groups based on height percentiles: <25% (Group I), 25-75% (Group II) and >75% (Group III). Cervical lengths were compared among groups. Correlations between cervical length and maternal height and statistically significant differences in cervical length among height percentile groups were the main outcomes.

RESULTS

Maternal height was positively but weakly correlated with first and second trimester cervical lengths (p=0.047, r=0.167 and p=0.039, r=0.197 respectively). The mean first trimester cervical lengths were significantly different between the groups (p=0.04). There were no significant differences, however, in the mean second trimester cervical lengths among the three groups although the difference was close to significance (p=0.06).

CONCLUSION

Although our results indicate a relationship between maternal height and cervical length in our population, maternal height seems to have only limited value in identifying women to be screened for shorter cervical length in a low risk asymptomatic population.

Maternal age and the size of White, Black, Hispanic, and mixed infants

OBJECTIVE

To clarify the interaction between maternal age and race in the prediction of infant size at birth.

METHODS

Birth certificate data was used to study the relationship between maternal age, race/ethnicity, and the size of term, singleton infants born to 91,061 healthy, non-smoking, non-substance using, primigravidas.

RESULTS

Maternal race/ethnicity (Black race: OR: 1.95, 95% CI: 1.49-2.56; Hispanic ethnicity: OR: 1.38, 95% CI: 1.19-1.61) and the interaction term, maternal age x race/ethnicity (OR: 1.06, 95% CI: 1.01-1.11) predicted small-for-gestational age (SGA) birth. The strength of the association between Black race and SGA delivery increased and the strength of the association between Hispanic ethnicity and SGA delivery decreased with age (P < 0.001 for trend). Thus, Black and Hispanic teenagers were more likely to have SGA babies than White teenagers (1.7% and 1.6%, respectively compared to 1.2%; P = 0.003). However, Black women who postponed childbearing until their mid-twenties were more likely to have SGA babies than their Hispanic and White counterparts (2.6% compared to 1.2%, and 1.0%, respectively; P < 0.0001).

CONCLUSION

The findings suggest that acquired maternal characteristic(s) cause the reproductive health of Black primigravidas to deteriorate and Hispanic primigravidas to improve with age.

A sonographic short cervix as the only clinical manifestation of intra-amniotic infection

OBJECTIVE

A sonographically short cervix is a powerful predictor of spontaneous preterm delivery. However, the etiology and optimal management of a patient with a short cervix in the mid-trimester of pregnancy remain uncertain. Microbial invasion of the amniotic cavity (MIAC) and intra-amniotic inflammation are frequently present in patients with spontaneous preterm labor or acute cervical insufficiency. This study was conducted to determine the rate of MIAC and intra-amniotic inflammation in patients with a cervical length < 25 mm in the mid-trimester.

STUDY DESIGN

A retrospective cohort study was conducted of patients referred to our high risk clinic because of a sonographic short cervix or a history of a previous preterm birth. Amniocenteses were performed for the evaluation of MIAC and for karyotype analysis in patients with a short cervix. Fluid was cultured for aerobic and anaerobic bacteria, as well as genital mycoplasmas. Patients with MIAC were treated with antibiotics selected by their physician.

RESULTS

Of 152 patients with a short cervix at 14-24 weeks, 57 had amniotic fluid analysis. The prevalence of MIAC was 9% (5/57). Among these patients, the rate of preterm delivery (< 32 weeks) was 40% (2/5). Microorganisms isolated from amniotic fluid included Ureaplasma urealyticum (n=4) and Fusobacterium nucleatum (n=1). Patients with a positive culture for Ureaplasma urealyticum received intravenous Azithromycin. Three patients with Ureaplasma urealyticum had a sterile amniotic fluid culture after treatment, and subsequently delivered at term. The patient with Fusobacterium nucleatum developed clinical chorioamnionitis and was induced.

CONCLUSION

(1) Sub-clinical MIAC was detected in 9% of patients with a sonographically short cervix (< 25 mm); and (2) maternal parenteral treatment with antibiotics can eradicate MIAC caused by Ureaplasma urealyticum. This was associated with delivery at term in the three patients whose successful treatment was documented by microbiologic studies.

Maternal anxiety and ultrasound markers for aneuploidy in a multiethnic population

OBJECTIVE

Discussion of isolated ultrasound (US) markers for fetal aneuploidy can provoke significant patient anxiety. The objective of this study is to quantify maternal anxiety associated with the detection of these markers.

METHODS

All patients undergoing routine second-trimester US examination for fetal anatomical survey over a one-year period were administered the State-Trait Anxiety Inventory (STAI) for Adults before and after the procedure. Women with isolated fetal markers for aneuploidy were notified of the findings but discouraged from pursuing amniocentesis. Rates of normal US examination, aneuploidy markers, anomalies, amniocentesis, and pregnancy outcomes were assessed across the ethnic groups. Pre- and post-ultrasound STAI surveys were scored and standardized with previously established norms. Student t-tests, Chi-square, and analysis of variance (ANOVA) were used where appropriate.

RESULTS

Among the 798 patients tested, 57% were Hispanic, 30% were Asian, 6% were Black, and 7% were White. Maternal anxiety level was decreased in women after a normal US. The anxiety level increased with aneuploidy markers and was the highest with anomalies. Aneuploidy markers were more common among Hispanic and Asian fetuses, without any associated aneuploidy. Women with isolated aneuploidy markers underwent amniocentesis as often as women with advanced maternal age.

CONCLUSION

The detection and communication of isolated aneuploidy markers is associated with increased maternal anxiety and unnecessary amniocentesis.

The epidemiology of preterm birth

The epidemiologic characteristics of women who deliver their infants before term birth are clues to the cause of this most important obstetric problem.

Does cervical length at 13-15 weeks' gestation predict preterm delivery in an unselected population?

OBJECTIVE

To assess the role of early mid-trimester cervical length measurement as a predictor of spontaneous preterm birth in an unselected population.

METHODS

In this prospective study, unselected, asymptomatic, Caucasian women with singleton pregnancies underwent standardized transvaginal ultrasonographic (TVS) cervical length measurement at 13-15 weeks' gestation as a screening test for preterm delivery (PTD). Women with multiple gestations, iatrogenic PTD, and previous cervical conization were excluded. The primary outcome measures were spontaneous PTD at < 37 and < 34 weeks. The correlation between cervical length and previous obstetric history was evaluated.

RESULTS

A total of 2469 patients met the inclusion criteria. The mean gestational age at cervical assessment was 14 + 2 weeks. The mean gestational age at delivery was 40 + 0 weeks. The rate of spontaneous deliveries before 37 weeks' gestation was 1.7%. In 0.2% the delivery occurred before 34 weeks' gestation. The mean +/- standard deviation cervical length for the entire population was 44.2 +/- 5.4 mm. No difference was observed between cervical length in women that delivered at term and those that delivered either before 37 or before 34 weeks' gestation. Previous obstetric history (prior preterm birth, previous miscarriages and terminations, and parity) did not affect cervical length at 14 weeks of gestation.

CONCLUSIONS

Performed at 14 weeks' gestation, TVS measurement of the cervical canal length to predict spontaneous PTD is not a reliable screening procedure.

Does incomplete growth and development predispose teenagers to preterm delivery? A template for research

Pregnant teenagers are in better physical condition, suffer from fewer chronic diseases, and engage in fewer health-risky behaviors than socioeconomically similar pregnant adults, but give birth to a disproportionately large number of preterm infants. This systematic review of the adolescent pregnancy literature defines the unique risks associated with being young and pregnant by examining how the physical and psychosocial changes that are characteristic of puberty and adolescence interact with traditional risk factors for preterm delivery. The need for age-specific interventions is discussed and recommendations for future research are made.

Changes in cervical length and the risk of preterm labor

OBJECTIVE

The purpose of this study was to assess the value of cervical length change as a predictor of preterm labor.

STUDY DESIGN

We used an historic cohort of 154 women to compare change in cervical length and preterm birth. Independent variables included cervical length at the first sonogram, absolute change of cervical length, and change per unit time. Covariates included age, parity, and history of preterm birth. Eligible patients had 2 or more sonograms that included cervical length.

RESULTS

The risk of preterm delivery increased as the length of the cervix declined, after an adjustment was made for the initial cervical length (P <.05). There were no significant interactions between initial length and the change of length; however, the highest rate of preterm deliveries occurred among women with a cervical length <3 cm at the first sonogram (23%). If the change in cervical length was expressed as a unit equal to a decline of 1 cm per month, the odds of giving birth to a preterm baby were 6.8-fold greater per unit change (P <.05).

CONCLUSION

A cervical length of <3 cm before 16 weeks of gestation is associated strongly with preterm birth; independently of baseline length, more rapid shortening of the cervix increases the risk of preterm birth.

Data mining methods find demographic predictors of preterm birth

BACKGROUND

Preterm births in the United States increased from 11.0% to 11.4% between 1996 and 1997; they continue to be a complex healthcare problem in the United States.

OBJECTIVE

The objective of this research was to compare traditional statistical methods with emerging new methods called data mining or knowledge discovery in databases in identifying accurate predictors of preterm births.

METHOD

An ethnically diverse sample (N = 19,970) of pregnant women provided data (1,622 variables) for new methods of analysis. Preterm birth predictors were evaluated using traditional statistical and newer data mining analyses.

RESULTS

Seven demographic variables (maternal age and binary coding for county of residence, education, marital status, payer source, race, and religion) yielded a .72 area under the curve using Receiving Operating Characteristic curves to test predictive accuracy. The addition of hundreds of other variables added only a .03 to the area under the curve.

CONCLUSION

Similar results across data mining methods suggest that results are data-driven and not method-dependent, and that demographic variables offer a small set of parsimonious variables with reasonable accuracy in predicting preterm birth outcomes in a racially diverse population.

Risk stratification and pathological mechanisms in preterm delivery

The delivery of infants before 37 weeks gestation is a leading cause of perinatal mortality and morbidity in the United States. Traditional methods of predicting women at risk relying on obstetric history or premonitory symptoms (detected clinically or by tocodynamometry) are neither sensitive nor specific. Recent approaches to predicting preterm delivery have included sonographic measurement of cervical length and various biochemical assays. Although more sensitive than traditional methods, none of these alone exhibits sufficient accuracy to warrant widespread use. We contend that the failure of current approaches to predicting preterm delivery reflects an inadequate understanding of the underlying pathogenesis. Clinical and experimental evidence support the concept that most cases of preterm delivery reflect four pathogenic processes, which share a common final biological pathway leading to uterine contractions and cervical changes with or without premature rupture of membranes. These pathogeneses are: (1) activation of the maternal or fetal hypothalamic-pituitary-adrenal axis; (2) decidual-chorioamniotic or systemic inflammation; (3) decidual haemorrhage (i.e. abruption); and (4) pathological distention of the uterus. Our research seeks to combine the most useful biophysical and biochemical markers of such processes with optimal clinical and epidemiological predictors into a composite, easily applied risk tool. This integrated approach has the potential to identify at-risk asymptomatic patients with high sensitivity, specificity, and positive and negative predictive values, and also to ascertain underlying pathogenic processes that can lead to targeted therapy. To accomplish these goals, we employ logistic regression and artificial neural network models to assess and apply the appropriate weight to markers associated with each of the above pathogenic pathways, in addition to markers of the final common pathway leading to fetal membrane rupture, cervical extracellular matrix degradation, and myometrial activation. By combining these markers, we expect ultimately to produce a predictive model that is more robust than any existing method, and that identifies the relative contribution of each pathogenic process. Further analysis of this model using a neural network will enable us to identify asymptomatic patients destined to deliver preterm with high sensitivity, specificity, positive and negative predictive values, and to assess the relative contribution of each of the four distinct pathogeneses to this preterm delivery risk.

Molecular epidemiology of preterm delivery: methodology and challenges

Preterm delivery (PTD) appears to be a complex trait determined by both genetic and environmental factors. Few studies have examined genetic influence on PTD. The overall goal of our study is to examine major candidate genes of PTD and to test gene-environment interactions. Our study includes 500 preterm trios, including 500 preterm babies and their parents and 500 maternal age-matched term controls. We will perform the transmission/disequilibrium test (TDT) on candidate genes thought to be important in each of the four biological pathways of PTD: (1) decidual chorioamionotic inflammation: interleukin 1 (IL-1), IL-6, and tumour necrosis factor (TNF); (2) maternal and fetal stress: corticotropin-releasing hormone (CRH); (3) uteroplacental vascular lesions: methylenetereahydrofolate reductase (MTHFR); and (4) susceptibility to environmental toxins: GSTM1, GSTT1, CYP1A1, CYP2D6, CYP2E1, NAT2, NQO1, ALDH2, and EPHX. We will also perform standard case-control analyses on the 500 preterm cases and 500 term controls to examine gene-environment interactions. The major environmental, nutritional and social factors as well as clinical variables known or suspected to be associated with PTD will be used to test for gene-environment interactions. This study integrates epidemiological and clinical data as well as genetic markers along major pathogenic pathways of PTD. The findings from this study should improve our understanding of genetic influences on PTD and gene-environment interactions.

Occupational fatigue and preterm premature rupture of membranes. National Institute of Child Health and Human Development Maternal-Fetal Medicine, Units Network

OBJECTIVE

The aim of this study was to prospectively determine the relationship between occupational fatigue and spontaneous preterm delivery segregated into the etiologically distinct categories of spontaneous preterm labor, preterm premature rupture of membranes, and indicated preterm delivery.

STUDY DESIGN

A total of 2929 women with singleton pregnancies at 22 to 24 weeks' gestation were enrolled in a multicenter (10 sites) Preterm Prediction Study. Patients reported the number of hours worked per week and answered specific questions designed to determine the following 5 sources of occupational fatigue described by Mamelle et al: posture, work with industrial machines, physical exertion, mental stress, and environmental stress. Fatigue was quantified (0-5 index) according to the number of these sources positively reported. Simple and Mantel-Haenszel chi2 tests were used to test the univariate association and hypothesis of a linear trend between sources of occupational fatigue and spontaneous preterm delivery. Covariables were considered by multivariate logistic regression analysis. Women who did not work outside the home were considered separately from those who worked but did not report any sources of occupational fatigue.

RESULTS

Each source of occupational fatigue was independently associated with a significantly increased risk of preterm premature rupture of membranes among nulliparous women but not among multiparous women. The risk of preterm premature rupture of membranes increased (P = .002) with an increasing number of sources of occupational fatigue-not working outside the home, 2.1%; working but not reporting fatigue, 3.7%; working with 1 source of fatigue, 3.2%; working with 2 sources of fatigue, 5.2%; working with 3 sources of fatigue, 5.1%; and working with 4 or 5 sources of fatigue, 7.4%. There was also a significant relationship (P = .01) between preterm premature rupture of membranes and an increasing number of hours worked per week among nulliparous women. Neither spontaneous preterm labor nor indicated preterm delivery was significantly associated with occupational fatigue among either nulliparous or multiparous women.

CONCLUSION

The occupational fatigue index of Mamelle et al discriminated a group of nulliparous women at increased risk for preterm premature rupture of membranes. The relationship between preterm premature rupture of membranes and occupational fatigue or hours worked may provide guidelines according to which nulliparous women and their employers can be advised.

Infant birth weight among women with or at high risk for HIV infection: the impact of clinical, behavioral, psychosocial, and demographic factors

The purpose of these analyses was to provide a prospective examination of the impact of HIV on birth weight using clinical, behavioral, psychosocial, and demographic correlates. HIV-positive (n = 319) and HIV-negative (n = 220) pregnant women matched for HIV risk factors (i.e., drug use and sexual risk behaviors) were interviewed during the 3rd trimester of pregnancy and 6 weeks postpartum. Medical chart reviews were also conducted for the HIV-seropositive pregnant women to verify pregnancy-related and birth outcome data. In a logistic regression analysis, model chi2(9, N = 518) = 124.8, p < .001, controlling for parity and gestational age, women who were HIV seropositive were 2.6 times more likely to have an infant with low birth weight. In addition, Black women and those who did not live with their partners were more than 2 times as likely to have infants with low birth weight, and those who smoked were 3.2 times more likely to have infants with low birth weight. Knowing that women with HIV, those who are Black, and those not living with a partner are at highest risk for adverse birth outcomes can help those in prenatal clinics and HIV specialty clinics to target resources and develop prevention interventions. This is particularly important for women with HIV because birth weight is associated with risk of HIV transmission from mother to child.

Patients with an ultrasonographic cervical length < or =15 mm have nearly a 50% risk of early spontaneous preterm delivery

OBJECTIVE

The aim of this study was to determine the value in the prediction of spontaneous preterm delivery of ultrasonographically measured cervical length measured between 14 and 24 weeks' gestation.

STUDY DESIGN

A retrospective cohort study examined cervical length by means of a two-stage procedure, transabdominal ultrasonography followed by transvaginal ultrasonography if cervical length was <30 mm.

RESULTS

A total of 6877 patients met inclusion criteria. Mean cervical length was 37.5 mm. Odds ratios for early preterm delivery (< or =32 weeks' gestation) for patients with cervical lengths < or =10, < or =15, < or = 20, < or =25, and < or =30 mm were, respectively, 29.3 (95% confidence interval, 11.3-75.8), 24.3 (95% confidence interval, 12. 9-45.9), 18.3 (95% confidence interval, 10.8-31.0), 13.4 (95% confidence interval, 8.8-20.6), and 3.2 (95% confidence interval, 2. 4-4.4). For early preterm delivery a cervical length of < or =15 mm had a positive predictive value of 47.6%, a negative predictive value of 96.7%, a sensitivity of 8.2%, and a specificity of 99.7%.

CONCLUSIONS

A short cervix seen on a second-trimester sonogram was a powerful predictor of early spontaneous preterm delivery (< or =32 weeks' gestation). Nearly 50% of patients with a cervical length < or =15 mm had an early spontaneous preterm delivery, which suggests that clinical trials of interventions (eg, cerclage) in this population are urgently needed.