Preterm Birth Research

CDC scientists are collaborating with many partners, including states, university researchers, and partners in health care to understand why preterm births occur and what can be done to help prevent them. The following are brief descriptions of projects supported by CDC’s Division of Reproductive Health.

1. It has been suggested that women who are deficient in Vitamin D may be at increased risk for complications of pregnancy, including preterm birth. Because this is a new and emerging concept, research is urgently needed to clarify this association. CDC is now funding such research using information collected from women and their infants as well as stored maternal blood. Vitamin D levels in maternal blood will be assessed in an effort to discover the nature of the relationship between vitamin D levels and preterm birth.
2. Birth certificates are the primary resource for determining the rate of preterm birth in the United States. Accurate recording of gestational age on these certificates is critical to calculate the rate of preterm delivery and better understand the impact of preterm birth and follow trends. CDC is sponsoring a set of pilot interviews with hospital personnel responsible for completing the birth certificate and their supervisors. The aims of this pilot study are to determine—
• How obstetric estimates of gestational age are collected for the birth certificate?
• Where the information for entering the obstetric estimate on the birth certificate is obtained?
• Where the information for entering the mother’s last normal menstrual period date is obtained?
• What processes, if any, are in place to ensure the obstetric estimate and the date of the mother’s last menstrual period are collected according to the National Center for Health Statistics (NCHS) recommendations and transferred accurately to the birth certificate. 
3. With investigators at Michigan State University, CDC is participating in cooperative research that builds on an NIH-funded, multi-ethnic community-based study of women from 52 prenatal clinics in 5 Michigan communities. The work of the CDC cooperative agreement expanded the Pregnancy Outcomes & Community Health (POUCH) study to evaluate in an integrated way, the social, clinical, and genetic biological factors associated with preterm birth.
4. In 2005, the NIH Maternal Fetal Medicine Network published results of a clinical trial that found that weekly injections of 17-alpha hydroxyprogesterone caproate (17P) was associated with a significant reduction of preterm birth among women with a history of prior preterm birth. To identify ways to translate these findings into clinical practice, and public health programs, CDC is participating in cooperative research with the University of Cincinnati to evaluate factors associated with acceptance of, use of, and adherence to 17P in the context of routine obstetrical care. The study will also investigate progesterone receptor genes of mothers and infants to explore possible mechanisms of action of 17P.
   Source: Meis PJ, Klebanoff M, et al. Does progesterone treatment influence risk factors for recurrent preterm delivery? Obstet Gynecol 2005;106(3):557–561. PMID #16135587.
5. A collaborative project with University of Kansas, University of Tennessee at Memphis, and CDC is investigating oxygen independent and oxygen dependent defense mechanisms of the lower and upper genital tract and genes associated with regulating the inflammatory cascade. The study of genomics and proteomics will explore if cervico-vaginal biomarkers associated with altered innate immunity can be used to identify women at risk weeks or months before onset of preterm delivery.
6. The vast majority of severe infant morbidity and mortality associated with preterm birth is due to very preterm birth (less than 32 weeks gestation). Information from large, population-based cohorts is needed to evaluate genetic, clinical, and social factors associated with very preterm birth and racial disparities in maternal and infant health. CDC, in collaboration with California Department of Health Services, California Birth Defects and Monitoring Program, and the March of Dimes Foundation,  is investigating the risk for very preterm birth using an existing large biobank of blood specimens from routine testing of pregnant women and infant blood spots from newborn screening. The biobank is linked to clinical information from medical record review, birth certificate data, prenatal screening data, newborn screening data, and geocoded data on neighborhood stressors. Genomic investigations will focus on endocrine and inflammatory pathway genes. In this way, social and biomedical factors and gene-environment interactions associated with very preterm birth can be evaluated among black, Hispanic, and white infants. Because of the large size of the biobank used for this study (specimens from approximately 600,000 births), this is a unique opportunity to examine the risk factors for very preterm birth, the contribution of both maternal and infant genetic factors, and factors in multiple racial and ethnic groups.
7. Although births less than 32 weeks gestation are at highest risk for infant morbidity and mortality, infants born at 34–36 weeks gestation account for most preterm births; this group, referred to as “late preterm birth.” The reasons why so many births occur at 34–36 weeks gestation are not clear. CDC researchers are conducting feasibility studies to determine if the reasons for delivery during the late preterm period can be identified in medical records. CDC researchers are also working with existing national databases to evaluate the consequences of late preterm birth, and identify reasons for the increased rate of late preterm birth. In addition, CDC has supported surveillance with the Commonwealth of Massachusetts that links birth records, maternal, infant, and child hospitalization records, and other clinical and public health databases. Known as the Pregnancy to Early Life Longitudinally Linkage (PELLL) database, this project has begun to explore the phenomenon of late preterm birth.