Siobhan Dolan, MD, MPH Assistant Professor of Obstetrics & Gynecology and Women’s Health

1. Genetics to Genomics: A Framework for Approaching Preterm Birth as a Common Complex Disorder Genetics, Genomics, Epidemiology, and MCHDecember 6, 2008 Siobhan Dolan, MD, MPH Assistant Professor of Obstetrics & Gynecology and Women’s Health Albert Einstein College of Medicine, Bronx, NY

3. Preterm Birth RatesUnited States, 1983, 1993, 2003, 2004* Percent Percent HP 2010 Objective 30 Percent Increase Preterm is less than 37 completed weeks gestation. Source: National Center for Health Statistics, final natality data Prepared by March of Dimes Perinatal Data Center, 2005

4. Objectives • Discuss risk factors and clinical approaches to preterm birth • Outline genetics and genomics principles • Introduce preterm birth as a common complex disorder • Propose a framework for a genomic approach to research in preterm birth

5. Changing Epidemiology of Preterm Birth Major categories of risk for preterm birth

6. Major Categories of Risk for Preterm Birth Extremes of maternal age Unintended pregnancy 34, 35, 36 weeks Maternal race Multiple gestation Cesarean section

7. Clinical Approaches to the Management of Preterm Birth

8. Types of Preterm Birth Spontaneous Preterm Labor Spontaneous Premature Rupture of the Membranes Preterm Birth Medical Intervention While this suggests distinct pathways, many of the risk factors for all 3 are similar.

9. Major Categories of Risk for Preterm Labor/Delivery General maternal issues: • Medical and Obstetric History • Behaviors • Genetics • Environmental

10. Risk Factors for Preterm Labor/Delivery • The best predictor of having a preterm birth is multifetal gestation or history of preterm labor/delivery • Other risk factors: • multifetal pregnancy • maternal age (<17 and >35 years) • black race • low SES • unmarried • previous fetal or neonatal death • 3+ spontaneous losses • uterine abnormalities • incompetent cervix • genetic predisposition • low pre-pregnant weight • obesity • infections • bleeding • anemia • major stress • lack of social supports • tobacco use • illicit drug use • alcohol abuse • folic acid deficiency

11. American Journal of Public Health, March 2004

12. Risk Factors for Preterm Labor/Delivery • The best predictor of having a preterm birth is multifetal gestation or history of preterm labor/delivery • Other risk factors: • multifetal pregnancy • maternal age (<17 and >35 years) • black race • low SES • unmarried • previous fetal or neonatal death • 3+ spontaneous losses • uterine abnormalities • incompetent cervix • genetic predisposition • low pre-pregnant weight • obesity • infections • bleeding • anemia • major stress • lack of social supports • tobacco use • illicit drug use • alcohol abuse • folic acid deficiency

13. Genetics:The study of the patterns of inheritance of specific traits.

14. Pedigree

15. Multifactorial - Neural Tube Defect

16. Preterm Birth is a Common Complex Disorder

17. Complex • “Complex genetic traits refer to those phenotypes not fitting patterns of Mendelian segregation and/or assortment but exhibiting a preferential familial clustering that cannot be explained by cultural or environmental causes.” Muenke et al. Genet Med 2004:6(1):1-15.

18. Complex Disorders • 1. Genetic contribution • 2. Environmental influences • 3. Gene-environment interactions

19. Complex Disorders • Genetic contribution • Familial aggregation • Recurrence of preterm birth • Racial disparity

20. The Risk of Preterm Birth Across Generations Objective: To examine the risk of preterm birth for mothers who themselves were born before term. 1405 preterm mothers 2781 term mothers Conclusions: An increased risk of preterm delivery exists for women who themselves were born before 37 weeks gestation. This risk is inversely correlated with the maternal gestational age at birth and is influenced by maternal age and parity. Porter et al. Obstetrics & Gynecology. 1997;90:63-67.

21. Genetic influence on birthweight and gestational length determined by studies in offspring of twins Objective: To determine the relative importance of genetic effects on birthweight, gestational length and small for gestational age. 868 monozygotic female twin pairs 1141 dizygotic female twin pairs Conclusions: Concordance rates and intra-class correlations for birthweight, gestational length and small for gestational age were consistently higher in monozygotic compared with dizygotic twins. Model fitting suggested heritability estimates in the range from 25% to 40%. ** PRETERM BIRTH = 36% (0.03 – 0.51) ** Clausson et al. BJOG. 107:375-381. 2000.

22. Maternal and Paternal Influences on Length of Pregnancy Methods: 77,452 boys and girls in the Medical Birth Registry of Norway who later became parents themselves. Records were linked between parents and children. Results: Gestational age of the child at birth increased on average 0.58 days for each additional week in the father’s gestational age (0.48-0.67) and 1.22 days for each additional week in the mother’s gestational age (1.21-1.32). Lie et al. Obstet Gynecol 2006;107:880-5.

23. Complex Disorders • Genetic contribution • Environmental influences • Gene-environment interactions

24. Complex Disorders • Environmental influences • Smoking • Infection • Stress

25. Complex Disorders • Genetic contribution • Environmental influences • Gene-environment interactions

26. Maternal Cigarette Smoking, Metabolic Gene Polymorphism, and Infant Birth Weight • Objective: To investigate whether the association between maternal cigarette smoking and infant birth weight differs by polymorphisms of 2 maternal metabolic genes: CYP1A1 and GSTT1. • 741 mothers with singleton livebirths • 174 ever smokers • 567 never smokers • 207 cases low-birth-weight or preterm • 534 controls Wang et al. JAMA. 2002;287:195-202.

27. Maternal Cigarette Smoking, Metabolic Gene Polymorphism, and Infant Birth Weight Conclusions: Maternal CYP1A1 and GSTT1 genotypes modified the association between maternal cigarette smoking and infant birth weight, suggesting an interaction between metabolic genes and cigarette smoking. Wang et al. JAMA. 2002;287:195-202.

28. A polymorphism in the promoter region of TNF and bacterial vaginosis: Preliminary evidence of gene-environment interaction in the etiology of spontaneous preterm birth Objective: To assess if the presence of symptomatic bacterial vaginosis amplifies the risk of spontaneous preterm birth in those with a “susceptible” TNF genotype (TNF-2). 125 cases: delivered before 37 weeks as a result of ruptured membranes or preterm labor 250 controls: delivered after 37 weeks Macones et al. AJOG. 2004;190:1504-8.

29. A polymorphism in the promoter region of TNF and bacterial vaginosis: Preliminary evidence of gene-environment interaction in the etiology of spontaneous preterm birth Group % TNF-2 carriers %TNF-2 carriers OR (95% CI) in cases in controls Overall 45% 23% 2.1 (1.7-4.5) BV Positive 69% 27% 6.1 (1.9-21.0) BV Negative 34% 22% 1.7 (1.0-3.1) Conclusion: This study provides preliminary evidence that an interaction between genetic susceptibilities (TNF-2 carriers) and environmental factors (BV) is associated with an increased risk of spontaneous preterm birth. Macones et al. AJOG. 2004;190:1504-8.

30. Genomics:All of the structure and function of an entire genome (e.g., the human genome), including its sequences, structures, regulation, interactions, and products.

31. Genome:All of the genetic material (DNA) belonging to a particular organism.

32. “HuGE”:Human Genome Epidemiology

33. Framework for a Genomic Approach to Preterm Birth

34. Pathways to Preterm Birth • Inflammation / Infection (ascending), 40% • Stress (maternal/fetal), 25% • Bleeding / Clotting Abnormality (thrombophilia, decidual hemorrhage, abruption), 25% • Abnormal Uterine Distension (stretching), 10%

35. Activation of Maternal/Fetal HPA Axis Inflammation Pathological Uterine Distention Decidual Hemorrhage Abruption • Infection: - Chorion-Decidual - Systemic • Multifetal Preg • Polyhydramnios • Uterine abnormalities • Maternal-Fetal Stress • Premature Onset of Physiologic Initiators Prothrombin G20210A Factor V Leiden Protein C, S, Z Type 1 Plasminogen MTHFR Interleukins IL-1, IL-5, IL-8 TNF-a Fas L Gap jct IL-8 PGE2 Oxytocin recep CRH E1-E3 Mechanical stretch Chorion Decidua + CRH CYP1A1 GSTT1 Susceptibility to Environmental toxins + MMPs proteases uterotonins pPROM Uterine Contractions Cervical Change PTB Adapted from: Lockwood CJ, Paediatr Perinat Epidemiol 2001;15:78 and Wang X, et al. Paediatr Perinat Epidemiol 2001; 15: 63

36. Common Complex Disorders • “From a public health perspective, genes with mutations that are less highly penetrant but much more prevalent have a greater effect on the population than genes that are highly penetrant but uncommon.” Guttmacher AE, Collins FS. Genomic Medicine – A Primer. N Engl J Med 2002:347(19):1512-1520.

38. Genomics ... • Allows us to consider genetic variation as the background for environmental influences • Encourages research to examine gene-environment interactions

39. Genomics ... • May enhance our understanding of the mechanisms of disease and allow us to target or expand clinical interventions and public health strategies

40. Prevalence of spina bifida and anencephaly among all 24 surveillance programs Mandatory Fortification Pre-fortification Optional Fortification 1995 1996 1997 198 1999 2000 2001 Teratology 2002; 66:33-39. Updated 6/2004.

41. Folate Metabolism Source: Cummings AM, Kavlock RJ. Crit Rev Toxicol 2004;34:461-85.

42. MTHFR Gene - 1p36.3 Botto, LD, Yang Q. 2000. Am J Epidemiol. 151:862. • Polymorphism (variant) at position 677 • Thymine is substituted for cytosine Association with NTDs: OR 95% CI • homozygotes 1.8 1.4-2.2 • heterozygotes 1.2 0.99-1.3

43. Genomics ... • Highlights the role of family history

44. Protocol for Folic Acid Assess Personal and Family History HighRisk Routine components of preconception & prenatal care + Targeted 4 mg folic acid supplement Average Risk Routine components of preconception & prenatal care

45. Hypothetical Protocol for Preterm Routine components of preconception & prenatal care Extremely High Risk + Targeted smoking cessation and weight reduction + Consider progesterone Assess Family History HighRisk Routine components of preconception & prenatal care + Targeted smoking cessation and weight reduction Average Risk Routine components of preconception & prenatal care

46. Genetic and Genomic approaches do not replace but can add to: • Community based interventions • Patient / Consumer education • Provider education • Equity in health outcomes and health care

47. Common Complex Disorders • “The study of genomics will most likely make its greatest contribution to health by revealing mechanisms of common, complex diseases, such as hypertension, diabetes, and asthma.” Guttmacher AE, Collins FS. Genomic Medicine – A Primer. N Engl J Med 2002:347(19):1512-1520.

48. Common Complex Disorders • “The study of genomics will most likely make its greatest contribution to health by revealing mechanisms of common, complex diseases, such as hypertension, diabetes, and asthma.” … birth defects and preterm birth. Guttmacher AE, Collins FS. Genomic Medicine – A Primer. N Engl J Med 2002:347(19):1512-1520.

49. Thank you for your attention!