Allen Wilcox, M.D., Ph.D.

Scientist Emeritus

Epidemiology Branch / Reproductive Epidemiology Group


A385 Rall Building
111 T W Alexander Dr
Research Triangle Park, NC 27709


Research Topics

Fertility and Early Pregnancy
Dr. Wilcox and his research group have helped to develop epidemiologic tools for the study of human reproduction. His group carried out a landmark study of early pregnancy that identified the earliest detectable pregnancy loss – that which occurs between implantation and clinical recognition. This study established that one-quarter of human pregnancies are lost before women know they are pregnant. The study also showed that women are fertile for an average of six days in each menstrual cycle ending on day of ovulation, and that intercourse is most frequent during the six fertile days of the cycle. Dr. Wilcox and his group have also developed some of the basic methods for assessing time to pregnancy (fecundability) as an epidemiologic endpoint, as well as showing the methodological pitfalls involved in such studies.

Birth Weight and Preterm Delivery
In a series of papers, Dr. Wilcox has developed a critique of low birth weight and preterm delivery as endpoints in perinatal research. Reduced birth weights can be a sensitive marker of fetal growth restriction but not necessarily an indicator of poor health. Similarly, preterm delivery is useful as an endpoint in itself, but not as a predictable marker of subsequent outcome. Moreover, routine adjustment for gestational age in studies of perinatal outcomes (an adjustment widely practiced) can cause considerable bias.

Fetal Development and Childhood Health
Dr. Wilcox and his colleagues carried out a population-based case-control study of babies born with facial clefts in Norway for the purpose of uncovering causes of clefts. This study has integrated data on environmental risk factors with genetic data to establish the role of candidate teratogens such as low folates, cigarette smoking, heavy alcohol consumption, and other factors as causes of facial clefts. This study is the major component of an international consortium pursuing genetic variants linked to facial clefts. Currently Dr. Wilcox is conducting a study of cerebral palsy within the two 100,000-baby birth cohorts established in Norway and Denmark. This is the largest study of cerebral palsy to include prospectively collected information on maternal exposures, as well as biological samples collected during pregnancy.


Dr. Wilcox received his undergraduate and medical degrees from the University of Michigan, and his PhD in epidemiology from the University of North Carolina. He arrived at NIEHS in 1979, where he helped to establish the epidemiology program and served as its Branch Chief from 1991 to 2001. Since 2001, he has been Editor-in-Chief of the journal Epidemiology. He is past president of the American Epidemiological Society (AES), the Society for Pediatric and Perinatal Epidemiologic Research (SPER), and the Society for Epidemiologic Research (SER). He holds adjunct faculty appointments at the University of North Carolina and Harvard University. In 2008 he was awarded an honorary Ph.D. by the University of Bergen (Norway). He is the author of Fertility and Pregnancy: An Epidemiologic Perspective, published in 2010 by Oxford University Press.

Selected Publications

  1. Wilcox AJ, Weinberg CR, O'Connor JF, Baird DD, Schlatterer JP, Canfield RE, Armstrong EG, Nisula BC. Incidence of early loss of pregnancy. N Engl J Med. 1988;319(4):189-94.

  2. Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby. N Engl J Med. 1995;333(23):1517-21.

  3. Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-9.

  4. Wilcox AJ. On the importance--and the unimportance--of birthweight. Int J Epidemiol. 2001;30(6):1233-41.

  5. Jukic AM, Baird DD, Weinberg CR, McConnaughey DR, Wilcox AJ. Length of human pregnancy and contributors to its natural variation. Hum Reprod. 2013;28(10):2848-55.

This page was last updated on June 24th, 2019