13
Nov
Prenatal Insecticide Exposure Linked to Negative Birth Outcomes in a Biomonitoring Study
(Beyond Pesticides, November 13, 2025) A study in Environmental Science & Technology shows that maternal exposure to organophosphate (OP) and pyrethroid insecticides adversely affects newborn health. Through amino acid and acylcarnitine metabolomics (the study of small molecules known as metabolites) with over 400 mother-infant pairs, this research analyzes metabolic pathways linking pesticide exposure to negative birth outcomes. “To our knowledge, this study is the first to reveal the effect of OP and pyrethroid insecticide exposure on neonatal metabolic signatures, which may elucidate a key role of metabolites in insecticide exposure and birth outcomes,†the authors state.
In collecting maternal urine samples in the first and third trimesters, as well as neonatal blood samples after birth, OP and pyrethroid metabolites and metabolomic biomarkers are assessed. Notably, the authors report: “Results indicated that third-trimester maternal urinary levels of 3- phenoxybenzoic acid (3-PBA) and diethyl dithiophosphate (DEDTP) were negatively associated with birth weight. Specifically, a one-unit increase in their ln-transformed [natural logarithm form] concentrations was associated with a 1.508% decrease in birth weight for 3-PBA and a 1.366% decrease for DEDTP.â€
Additionally, the analyses show that OP and pyrethroid exposure is associated with “disrupted neonatal amino acids and acylcarnitine profiles, with patterns varying by trimesters and sexes.†As a novel study, this research reveals a link between neonatal metabolomics and OP/pyrethroid exposure to developmental toxicity not previously seen, which, as the authors explain, suggests “that disruptions in acylcarnitine-mediated energy metabolism may contribute to adverse birth outcomes.â€
Study Importance and Background
The widespread use of organophosphate and pyrethroid insecticides across the globe, for both agricultural and urban pest control, presents a threat to human health and the environment. Exposure to OPs and pyrethroids can occur through dietary intake, as well as through the air or skin with residential applications and agricultural activities. As Beyond Pesticides has documented (see below), these compounds have a wide range of adverse effects including neurotoxicity, cardiotoxicity, hepatotoxicity, and respiratory failure, among others.
The researchers note: “The detection rates of urinary OP and pyrethroid metabolites in general populations across different countries and regions typically exceed 60%, indicating widespread human exposure to these pesticides. OP and pyrethroid insecticides are able to cross the placental barrier into the fetal environment, and their metabolites have been detected in cord blood, placenta, and amniotic fluid. Therefore, continuous exposure to these insecticides indicates that potential health risks may be present, especially during pregnancy, as fetuses are highly vulnerable to the effects of environmental hazards.â€
Understanding the effects of prenatal exposure to pesticides is crucial, as fetal and infant development influence long-term health outcomes. At delivery, important fetal growth measures are assessed, including birth weight, birth length, and gestational age, which are also risk factors for future morbidity (diseases) during infancy and adulthood.
Both amino acids and acylcarnitines are “key biomarkers reflecting the most critical determinants of neonatal development, particularly nutritional and metabolic status,†the authors share. While amino acids serve as the building blocks for protein synthesis and tissue supply, which plays an important role in maintaining protein homeostasis throughout the body, acylcarnitines are fatty acid metabolites that are involved with numerous processes for metabolism.
Methodology and Results
The researchers, in conducting a prospective cohort study of 406 mothers and their newborns, “investigate the associations between maternal exposure to OP and pyrethroid insecticides, neonatal birth outcomes, and alterations in neonatal amino acid and acylcarnitine metabolomic profiles.†By employing repeated biomarker measurements during both early and late pregnancy, this study provides “more precise epidemiological evidence for identifying critical exposure windows linking OP and pyrethroid exposure to adverse neonatal outcomes,†the authors state. They continue, “More importantly, our findings offer novel insights into how prenatal exposure to these insecticides in humans may disrupt fetal development through amino acid and acylcarnitine metabolic pathways.â€
Maternal urine samples were collected during the first and third trimesters and analyzed for five nonspecific OP metabolites (dimethyl phosphate (DMP), diethylphosphate (DEP), dimethyl thiophosphate (DMTP), dimethyl dithiophosphate (DMDTP), and diethyl dithiophosphate (DEDTP)), as well as a nonspecific metabolite of up to 20 pyrethroids (3-phenoxybenzoic acid (3-PBA)) and a specific metabolite of cyfluthrin and flumethrin (4-fluoro-3-phenoxybenzoic acid (4F-3PBA)).Â
After babies were born, trained medical staff collected the newborn data and heel-prick blood samples between 48−72 hours post-delivery. The blood samples were analyzed for a total of 12 amino acids and 26 acylcarnitines that play a role in metabolism and development.
The results include:
- A 100% detection rate of all metabolites.
- 3-PBA, DMP, DEP, DMTP, and DMDTP show detection in over 80% of urine samples.
- “[C]oncentrations of most OP metabolites (DMP, DEP, DMTP, and DMDTP) were significantly higher in the third trimester.â€
- The highest concentration overall is observed for the OP metabolite DMP.
- Seven metabolites are significantly associated with first-trimester OP and pyrethroid insecticide exposure.
- “The analysis revealed significant negative associations between third-trimester insecticide metabolite levels and birth weight… Urinary insecticide metabolite concentrations exhibited a negative joint effect on birth weight during the third trimester of pregnancy and across pregnancy-average.â€
- 3-PBA exhibits the strongest association for neonatal metabolites for pesticide exposures averaged over the entire pregnancy.
- “[T]he association between insecticide exposure and birth outcomes was statistically more significant in male infants. When analyzing the relationships between maternal urinary insecticide metabolites and neonatal endogenous metabolites by infant sex, DMP and DEP showed stronger associations with metabolites in male infants.â€
- The data suggests that “third-trimester insecticide exposure may potentially impair fetal development by interfering with critical energy metabolism pathways, such as glucose metabolism and fatty acid β-oxidation.â€
In summary, the researchers say: “Overall, our repeated measures revealed that third-trimester insecticide exposure had the most significant effect on birth outcomes. This could be largely attributed to the fact that the third trimester is a critical period in human fetal development, where fetal growth and birth weight exhibit the greatest susceptibility to environmental impacts.â€
They continue: “Our metabolomics findings suggest that that OP/pyrethroid insecticide exposure throughout pregnancy may influence neonatal neurodevelopment, methylation processes, and energy metabolism… More importantly, our identification of metabolite-mediated pathways provides new insights into the potential mechanisms by which prenatal exposure to insecticides may affect fetal development.â€
Previous Research
The authors cite numerous other biomonitoring and epidemiologic studies that support the findings of health threats from OP and pyrethroid insecticides. As they point out, however, many of the studies that also analyze urine samples rely on a single sample and could potentially underestimate exposure, while the current study captures multiple sampling periods. The referenced study results include:
- Prenatal insecticide exposure is linked to an increased risk of preterm birth and lower birth weight. (See research here, here, and here.)
- In one study, higher pyrethroid metabolite concentrations in maternal urine samples are associated with increased neonatal weight and gestational age.
- “Analysis of 858 mother−infant pairs in a Danish cohort revealed that male infants in the third tertile of maternal OP exposure exhibited a longer gestational age compared to those in the first tertile.â€
- A study of 248 pregnant Thai farmworkers shows negative effects of prenatal OP and pyrethroid exposure on the placental transcriptome.
- Another study of pregnant Thai farmworkers, with elevated chlorpyrifos exposure, “observed perturbations in maternal serum metabolites involved in glutathione metabolism and fatty acid oxidationâ€, which relate to energy metabolism and oxidative stress pathways.
- Research regarding “dietary pesticide intake among U.S. adults reported alterations in energy and vitamin metabolism pathways, while an intervention study in children found that switching to an organic diet reduced urinary biomarkers of oxidative stress and inflammation. (See here and here.)
- One study demonstrates the “association between prenatal pyrethroid exposure and disrupted neonatal lipid metabolism, with elevated urinary metabolite concentrations correlating with increased levels of cord blood triglycerides,†among other results.
- “A cross-sectional study of pregnant agricultural workers in rural northern China showed that higher levels of total urinary pyrethroid metabolites at delivery were associated with lower birth weight.â€
- Additional research finds positive correlations between first-trimester urinary 3-PBA concentration and birth weight in a pregnant women cohort in China.
- Another study from China “that measured 4F-3PBA levels only during the first trimester also reported a positive association between urinary 4F-3PBA levels and birth length.â€
Previous coverage from Beyond Pesticides also documents the negative implications from exposure to organophosphate and pyrethroid insecticides, particularly regarding infant development. Recent Daily News includes Organophosphate Pesticide Drift from Agricultural Fields Elevates Risk for Pregnant Farmworkers, Study Finds Reproductive System Effects in Adolescents with Prenatal Pesticide Exposure, and Childhood, Prenatal Pesticide Exposure Impacts Immune System, According to Study, as well as coverage linking OPs and pyrethroids to ADHD and neurodevelopmental problems (see here, here, here, here, here, and here), lower IQs (see here and here), adverse birth outcomes (see here, here, and here), issues with sleep, rare eye cancer, behavioral issues, and decreased lung function.
The Organic Solution
The link between prenatal pesticide exposure and negative birth outcomes is one of many threats to health that has been linked to environmental contaminants for which safer alternatives exist. As shared during the first session of Beyond Pesticides’ 42st National Forum Series— The Pesticide Threat to Environmental Health: Advancing Holistic Solutions Aligned with Nature, we are all affected by how land is managed, food is grown, and nature is protected. Different experiences and perspectives may bring us to care about health and the environment and the devastating adverse effects of pesticides and toxic substances. However, ensuring a livable future requires us to cultivate a collective concern about daily decisions on the management of our personal and community spaces, the practices used to grow the food we buy, and the care that we as a society give to complex and fragile interrelationships that sustain the natural world on which we depend.Â
A recording for the first session is now live! See how the four speakers at the Forum give us an opportunity to step back, widen the lens, and think about redefining our relationship with nature in all aspects of our practices and advocacy here. Register here for the second session on December 4th from 1:00 – 3:30 PM Eastern.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Ma, Y. et al. (2025) Prenatal Insecticide Exposure and Adverse Birth Outcomes: Evidence for Mediation via Disruptions in Amino Acid and Acylcarnitine Metabolism, Environmental Science & Technology. Available at: https://pubs.acs.org/doi/10.1021/acs.est.5c13454.
