02
Dec
Research Finds Maternal Pesticide Exposure Impacts Reproductive Hormones in Infant Girls
(Beyond Pesticides, December 2, 2025) Recently published in Reproductive Toxicology, researchers in Denmark and Iceland investigate the impacts of pesticides on sex hormones, finding that “prenatal exposure to [the insecticide] chlorpyrifos and [weed killer] 2,4-D may affect the reproductive hormones in girls, but not boys, during minipuberty, which may have long-term implications.†Based on their analysis of urinary maternal concentrations of the pesticides and their metabolites and hormone levels in infants, the authors report, “This study examined the association between maternal pesticide exposure and pituitary, gonadal, and adrenal hormones in offspring during infancy.†The sex-specific findings highlight a public health concern with potentially long-lasting transgenerational effects.
“We recruited pregnant women from 2010 to 2012 in the Odense Child Cohort, including 489 mother-child pairs,†the authors state. They continue: “Maternal urinary concentrations of the generic pyrethroid metabolite 3-phenoxybenzoic acid (3-PBA), the chlorpyrifos metabolite 3,5,6-trichloro-2-pyridinol (TCPY), and the herbicide 2,4-D were measured at gestational week 28. Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), estrone (E1), estradiol (E2), 17-hydroxyprogesterone (17-OHP), Androstenedione (Adione), and Dehydroepiandrosterone sulfate (DHEAS) were assessed in infancy.â€
The results of the analyses show that in girls, higher maternal urinary TCPY and 2,4-D concentrations are significantly associated with LH levels, which are hormones produced by the pituitary gland that trigger ovulation and regulate the menstrual cycle. Additional associations, specific to girls, between maternal levels of 3-PBA, TCPY, and 2,4-D and lower LH, FSH, E1, and E2 are also noted. The strongest associations are noted with the chlorpyrifos metabolite (TCPY) and 2,4-D, while the metabolite of many pyrethroids (3-PBA) shows slightly weaker results. No associations are seen in boys within this study.
“Our findings suggest that, even in this low-exposed cohort, prenatal exposure to the insecticide metabolite TCPY and the herbicide 2,4-D causes persisting alterations of the HPG axis [hypothalamic-pituitary-gonadal axis that controls reproduction] in healthy infant girls,†the researchers say. “This raises public health concerns, as all participants were exposed to TCPY and 2,4-D, the latter of which remains widely used.â€
Background
Chlorpyrifos, an organophosphate insecticide, was widely used in the European Union prior to the 2020 ban, which stemmed from concerns about developmental neurotoxicity and carcinogenicity. The persistence of chlorpyrifos, however, leads to detection years after use in the environment. 2,4-dichlorophenoxyacetic acid (2,4-D), phenoxyacetic acid herbicide, remains widely used to control broadleaf weeds. Both of these pesticides are registered by the U.S. Environmental Protection Agency (EPA) for use in crop production and on golf courses. However, there are certain state-level restrictions, such as in Hawaii, Maryland, Washington, Oregon, and California.
“In the general population, pesticide exposure primarily occurs through diet, particularly via residues in cereals, fruits, and vegetables,†the authors state. They continue: “Insecticides are rapidly metabolised and primarily excreted in urine within 24 h, whereas 2,4-D is largely excreted unmetabolized, making urinary biomarkers effective for monitoring exposure to both compound classes.â€
Comparing maternal urinary concentrations of pesticides to impacts on infants highlights cascading implications to future generations. As the researchers describe: “Shortly after birth, the hypothalamic-pituitary-gonadal (HPG) hormone axis is transiently activated, resulting in increasing blood concentrations of gonadotropins and sex hormones well within the reference range for adults. This brief hormone peak during the first six months after birth is referred to as minipuberty, after which reproductive hormone levels remain low until puberty. Minipuberty allows for the maturation of sexual organs and could serve as a window of opportunity for reproductive function during adulthood and may be a sensitive marker of affected early gonadal development during the male programming window.â€
Beyond Pesticides has a long history of covering the impacts on infants and children from pesticide exposure. Children face much higher hazards than adults from pesticide exposure. Their small size and developing organ systems, propensity to crawl and play near the ground, tendency for frequent hand-to-mouth motion, and greater intake of air and food relative to body weight make them particularly susceptible. Many of these risks start before a child is born, indicating the need for pregnant mothers to take particular care to avoid contact with hazardous pesticides.
Study Methodology and Results
The 489 mother-child pairs, with 45% of the infants as female, included in the study are derived from the Odense Child Cohort (OCC), a longitudinal Danish birth cohort including women pregnant between 2010 and 2012. From the mothers, fasting spot urine samples were collected in gestational week 28. “The urine samples were analysed for 3-PBA (a common metabolite of most pyrethroids and therefore a biomarker for the combined exposure to mixtures of pyrethroids), TCPY (a metabolite of both the organophosphate chlorpyrifos and the sister-compound chlorpyrifos-methyl), and 2,4-D (an herbicide),†the authors explain.
Serum samples of reproductive hormones were obtained from the infants at a mean age of 3.8 months. “We used multivariate linear regression analysis to investigate associations between maternal urinary concentrations of pesticide biomarkers and hormone standard deviations during minipuberty in the offspring, stratified by sex,†the researchers state.
As a result, most maternal urine samples show detectable concentrations of 3-PBA (93%), TCPY (91%), and 2,4-D (97%), and the analyses reveal that the concentrations of pesticide metabolites are inversely associated with circulating levels of reproductive hormones in girls. “Generally, there was a trend towards lower hormone levels (i.e., LH, FSH, E1, and E2) with increasing maternal urinary concentrations of 3-PBA, TCPY, and 2,4-D in girls,†the authors report. “Concerning boys, there were no associations between maternal concentrations of 3-PBA, TCPY, and 2,4-D and reproductive hormones… Our findings suggest that prenatal pesticide exposure may affect pituitary and/or hypothalamic function in infant girls, potentially altering normal endocrine activity.â€
Previous Research
A wide of science exists connecting chlorpyrifos and 2,4-D, among many other pesticide active ingredients, to deleterious health implications, labeling them “as potential endocrine disruptors capable of interfering with sex hormone activity in vitro, primarily by affecting androgen function.†(See here, here, and here.) The researchers continue: “Thus, these compounds may pose risks during early development. Fetal exposure may interfere with fundamental epigenetic modifications, potentially impairing organ development.â€
To the authors’ knowledge, only one previous study in humans examines the potential effects of pesticide exposure during pregnancy on reproductive hormones during minipuberty, but only includes boys. “They found trends towards reduced testosterone (T) levels and increased ratio of luteinizing hormone (LH) to T in exposed boys, and also increased follicle stimulating hormone (FSH), suggesting impaired testicular function and compensated increase of gonadotropin levels, in 113 sons of women working in greenhouses in Denmark,†the researchers summarize.
Additional experimental studies are consistent with the findings in the current study:
- “Animal studies suggested that exposure to chlorpyrifos during pregnancy may cause persisting alterations in hypothalamic function. Such effects may impair the activity of the HPG axis, including reduced gonadotropin secretion.†(See here, here, and here.)
- “In silico studies suggest that chlorpyrifos may compete with progesterone, act as a potent androgen disruptor, and interfere with estrogen signaling by binding to their respective receptors, where it functions as a ligand.†(See here, here, here, and here.)
- “Similarly, some pyrethroids have demonstrated estrogen receptor activation in vitro and in vitro and in vivo models. If these effects persist in adolescence, follicular growth and ovulation could be affected.†(See here, here, here, here, and here.)
The study authors, in previous research, also “evaluated maternal urinary concentrations of 3-PBA, TCPY, and 2,4-D in relation to infant anogenital distance (AGD; distance from anus to genitals) in 322 girls and 419 boys from the OCC [Odense Child Cohort].†The results show that prenatal exposure to 2,4-D is associated with reduced AGD in infant boys. While that study reports no associations in girls, the “current findings suggest that hormone concentrations during female minipuberty may be a more sensitive outcome of low exposure compared to female infant AGD.â€
As stated by Rossella Cannarella, M.D., PhD in a report released by the Health and Environment Alliance (HEAL): “Mounting scientific evidence links exposure to harmful environmental chemicals—such as endocrine disrupting chemicals (EDCs), persistent pollutants, and microplastics—to a range of serious male health outcomes, including prostate and testicular cancer, infertility, sexual dysfunction, hormonal imbalances, and impacts on descendants’ health.â€
Dr. Cannarella continues, saying: “Chemicals are everywhere: People are exposed daily to EDCs and toxic substances through food, drinking water, air, personal care products, and occupational settings. Common culprits include phthalates (found in plastics), PFAS (in waterproof products, and as contaminers in other products, including food and drinking water), bisphenols (in food containers), and pesticides—many of which interfere with hormone systems and reproductive development.†To learn more about the threats from environmental contaminants to health, hear Dr. Cannarella and the founder and director of HEAL, Génon Jensen, speak at the second session of the 42nd National Forum—The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature—on December 4. Register here.
The Organic Solution
Chlorpyrifos and 2,4-D are just two pesticide active ingredients, out of thousands, that threaten health and the environment. The only way to mitigate their impacts is to adopt a widespread transition towards organic agriculture and land management. To get involved in this holistic solution, take action to tell your governor to adopt policies that support organic land management and ecological balance here.
Pesticide residues readily contaminate all ecosystems and are prevalent in soils, water (solid and liquid), and the surrounding air. Scientific literature demonstrates pesticides’ long history of adverse effects on the environment, including wildlife, biodiversity, and human health. Organic agriculture, with its requirement to conserve (preserve and increase) biodiversity, is based on a worldview valuing long-term sustainability in which humans share Earth’s bounty. If humans are to persist on this planet, the balance of life must be supported. Learn more about the many health and environmental benefits of organic practices here and here.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Iversen, A.-P. et al. (2025) Prenatal exposure to the pesticides chlorpyrifos and 2,4-Dichlorophenoxyacetic acid is associated with circulating levels of reproductive hormones in healthy infant girls, Reproductive Toxicology. Available at: https://www.sciencedirect.com/science/article/pii/S0890623825002837.
