Allen Wilcox

During his influential, nearly four-decade-long career at the forefront of human reproduction research, Dr. Allen Wilcox has produced groundbreaking studies that have fundamentally changed our understanding of fertility and pregnancy.

A senior investigator at the National Institute of Environmental Health Sciences, Wilcox has studied the critical time period from conception to birth, and how specific environmental factors might affect reproduction and development. His research spans the spectrum of reproductive health from fertility and miscarriages to fetal growth and birth defects.

“Allen is viewed as the father of the epidemiologic study of human reproduction. He has defined the field over his 37-year career,” said Dr. Darryl Zeldin, scientific director at the institute, which is part of the National Institutes of Health. “Allen has made discoveries that have enhanced our knowledge of fertility, pregnancy and reproduction.”

Wilcox, who as a medical student had a strong interest in obstetrics and pediatrics, joined the institute in 1979 when little attention had been paid to the epidemiology of human reproduction.

“I can’t imagine anything more exciting than finding a field that is not well-plowed, and that still has basic questions and problems to be addressed,” Wilcox said. “I wanted a workplace that would let me explore human reproduction as a research area, and the institute encouraged me to go for it. It was a real gift for a young investigator.”

Without much public health data available on miscarriages and why they occur, Wilcox decided to focus his first study on early pregnancy.

The four-year study looked at 221 women who were trying to become pregnant. Wilcox tested daily urine samples for the key hormone marker of pregnancy to identify pregnancy at the earliest possible time, around implantation. Wilcox was the first to show that 25 percent of pregnancies are lost before women are even aware they are pregnant. When recognized miscarriages are added, one-third of all pregnancies fail to survive to birth. His landmark study, which made the cover of Newsweek, also found that most women who have miscarriages are fertile and subsequently are able to have a healthy pregnancy.

“It took a very creative, meticulous and methodical approach to answer the questions about when a woman can conceive and what proportion of conceptions go on to be babies,” said Dr. David Savitz, vice president for research at Brown University.

“Allen had the courage to delve into fundamental challenges around reproduction,” he said.

The data from the early pregnancy study provided new insights into other aspects of human reproduction, including fertility. Wilcox’s work found that women are able to conceive during the five days leading up to ovulation, and the day of ovulation itself, which is valuable information for women trying to become pregnant.

The study also uncovered an error in the information companies provided to women about how to use standard over-the-counter pregnancy tests. Wilcox showed that the widely-used tests were not reliable in detecting pregnancy, as advertised, on the first day that a woman’s menstrual cycle was late. This finding led to more accurate guidelines.

Wilcox also upended conventional thinking around birth weight. Researchers and policymakers cited low birth weight as the major cause of perinatal death, but Wilcox’s series of methodological papers showed birth weight was a secondary factor, prompting researchers to focus more on the direct causes, including pre-term delivery and fetal pathology. 

His “singular talent is being able to identify really important problems and find the data to answer those problems in very clear and accurate ways,” Zeldin said.

Wilcox now is conducting a major study of cerebral palsy. This devastating disorder has often been attributed to accidents at birth, but Wilcox said the causes usually precede delivery. Combining the world’s two largest birth studies in Denmark and Norway, he and his colleagues are trying to identify prenatal factors and environmental exposures that lead to cerebral palsy. Peers in the scientific community believe those discoveries have the potential to radically change how researchers and people view the condition. 

“Allen is tackling fascinating scientific questions that have profound impact for families and society,” Savitz said. “He is undaunted.”

During the course of his long career, Wilcox has published more than 200 peer-reviewed papers and written two books, 10 book chapters and more than 50 editorials and commentaries.

He credits the thrill of discovery for keeping him motivated to address new questions, and to uncover results that may be unexpected. He also credits his colleagues, who he says are “brilliant” and “have been crucial to the success of these studies.”

“If my work makes a contribution, it has probably not been a single study,” Wilcox said, “so much as an approach to how all these separate pieces–fertility, conception, fetal development, infant survival—fit into an integrated picture. You can’t understand one without considering them all.”