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

Scientist Emeritus

Epidemiology Branch / Reproductive Epidemiology Group


David P Rall Building
111 Tw 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 established a 25% loss of human pregnancies 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. More recently, Dr. Wilcox estimated the loss of fertilized ova before implantation (a biologically undetectable loss) as 40 – 50%. Dr. Wilcox and his group have also developed some of the basic methods for assessing time to pregnancy (fecundability) as an epidemiologic endpoint, now widely used.

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. He has shown that birthweight is a biomarker of risk, rather than a direct cause of increased risk. Routine adjustment for birthweight (and also for gestational age) in studies of perinatal outcomes 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, integrating 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. Dr. Wilcox has also conducted a study of cerebral palsy within the two 100,000-baby birth cohorts 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 Ph.D. 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 – 2001. He was Editor-in-Chief of the journal Epidemiology from 2001 – 2014. He was made an Emeritus Scientist at NIEHS in 2019, where he continues an active research program. He is past president of the American Epidemiological Society, the Society for Pediatric and Perinatal Epidemiologic Research, and the Society for Epidemiologic Research. He has held adjunct faculty appointments at the University of North Carolina and Harvard University. In 2008 he was awarded an honorary doctoral degree 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, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-9.
  3. Wilcox AJ. On the importance--and the unimportance--of birthweight. Int J Epidemiol. 2001;30(6):1233-41.
  4. Wilcox AJ, Harmon Q, Doody K, Wolf DP, Adashi EY. Preimplantation loss of fertilized human ova: estimating the unobservable. Hum Reprod. 2020;35(4):743-750.

Related Scientific Focus Areas

This page was last updated on Friday, January 21, 2022