Robert F. Kennedy Jr. used a White House event focused on maternal health to deliver a stark warning about male fertility in the United States, declaring that declining sperm counts and testosterone levels among young Americans represent "an existential crisis for our country" - remarks that immediately triggered debate among scientists over how accurately he portrayed the underlying research.
Speaking during the May 11 launch of the federal Moms.gov initiative alongside Donald Trump, Kennedy framed reproductive decline as one of the defining public health emergencies facing the country. The new platform is designed to provide resources related to pregnancy, maternal care, nutritional support and fertility treatment access.
"President Trump has directed my agency to find out the cause of the fertility crisis," Kennedy said during the Oval Office gathering, according to remarks reported by Raw Story. He continued: "The fertility crisis for women began in 2007. For men, in 1970, men had twice the sperm count as our teenagers do today."
Kennedy tied the issue to broader demographic trends, noting that the U.S. fertility rate has fallen to 1.57, well below the 2.1 replacement rate generally considered necessary to maintain population stability without immigration. He warned the country risked moving toward the same demographic challenges confronting Japan and China.
The remarks were consistent with Kennedy's broader public messaging on reproductive health. During a 2025 appearance on Fox News with Jesse Watters, Kennedy claimed: "a teenager today, an American teenager, has less testosterone than a 68-year-old man" and argued that "sperm counts are down 50 per cent," calling the trend "an existential problem."
Kennedy has repeatedly blamed environmental factors, particularly pesticides and endocrine-disrupting chemicals, for declining fertility rates. He described modern women as "walking around" in a "toxic soup" that damages reproductive health, language that has become central to his broader environmental-health agenda.
Some elements of Kennedy's warning are grounded in peer-reviewed research. The sperm-count data he referenced appears linked to a widely cited 2022 meta-analysis published in Human Reproduction Update by researchers Hagai Levine and Shanna Swan.
That study analyzed global semen data collected between 1973 and 2018 and found sperm concentration among men in North America, Europe and Australia declined by more than 50% during the period studied. The researchers also concluded that the pace of decline appeared to accelerate in the 21st century and increasingly extended into regions outside the West.
Levine described the findings as "a canary in a coal mine," urging governments and health systems to reduce environmental exposures potentially affecting reproductive health. Swan separately warned the issue extended beyond fertility itself, linking low sperm counts to broader health concerns including hormonal disruption and increased disease risk.
Yet scientists say Kennedy's most attention-grabbing claims stretch beyond what the available data actually shows.
The Levine-Swan studies focused on adult men, not teenagers specifically. Angela Rasmussen, who reviewed existing literature on adolescent reproductive health, noted that large-scale population studies measuring sperm counts in healthy teenage boys are extremely limited.
The few existing studies, Rasmussen said, often focus on highly specific clinical populations rather than representative samples of adolescents.
Experts also challenged Kennedy's testosterone comparison between teenagers and older men. Testosterone naturally peaks during late adolescence and early adulthood before gradually declining with age, making the suggestion that modern teenagers broadly possess lower testosterone than healthy men in their late 60s biologically questionable without substantial supporting evidence.
Scott Lundy told NBC News that research into sperm-count decline remains "very contentious," adding that "for every paper that suggests a decline and raises an alarm, there's another paper that says the numbers aren't changing."
Methodological debates surrounding the Levine-Swan research have also persisted. Critics including Stephanie Lamb have argued that semen collection and testing standards varied significantly between laboratories included in the analysis, potentially complicating long-term comparisons across decades and countries.
Separate research from the Cleveland Clinic in 2022 found sperm concentrations among fertile American men remained relatively stable, highlighting the distinction between studies of general populations and studies focused specifically on men with proven fertility.
Even so, researchers broadly agree that some underlying trends Kennedy references deserve serious attention. A 2021 study cited by The Frontier found declining testosterone levels among adolescent and young adult males over the past two decades, with obesity and sedentary lifestyles strongly associated with lower hormone levels.
Environmental exposure concerns have also gained scientific traction. A 2023 review published in Environmental Health Perspectives identified significant associations between exposure to organophosphate and carbamate insecticides and lower sperm concentrations in men.
