Pregnancy Exposure to Phthalate Replacement Chemical DINCH Tied to Smaller Newborns

A chemical that was introduced to the plastics industry as a safer substitute for phthalates, a family of additives now widely recognized as harmful, may itself be interfering with fetal growth, according to one of the largest investigations of its kind published to date. The new research, led by scientists at NYU Langone Health and NYU Grossman School of Medicine and published online on October 4 in the journal Environment International, analyzed 6,617 pregnancies across the United States and found that pregnant women with higher levels of the chemical diisononyl cyclohexane-1,2-dicarboxylate, known commercially as DINCH, in their urine gave birth to babies who were measurably lighter and smaller than those born to women with lower exposure levels. The findings arrive at a moment when regulators, manufacturers, and public health advocates are wrestling with a recurring pattern in chemical safety: replacements for well-documented toxicants entering the market before their own biological effects are fully understood.

Phthalates are a class of synthetic chemicals used to make rigid plastics flexible and durable, and they are found in an enormous range of everyday products, including food packaging, medical devices, vinyl flooring, and children’s toys. Over the past two decades, a growing body of epidemiological and laboratory evidence has linked phthalate exposure to an increased risk of premature birth, infertility, and other health concerns, prompting manufacturers to seek alternatives. DINCH emerged as one of the most prominent of these substitutes and has been marketed as a plasticizer with a more favorable safety profile. The new study suggests, however, that the assumption of safety may deserve closer scrutiny, because higher maternal DINCH levels were consistently associated with reduced newborn size, a marker that clinicians consider an important early indicator of lifelong health risk.

The scale of the association was quantified precisely by the research team. Every tenfold increase in exposure to DINCH corresponded to a 27-gram reduction in newborn birth weight. While 27 grams may appear modest in isolation, the researchers emphasize that even small differences in birth size can matter significantly at the population level. Fetal growth problems can raise the risk of heart disease, learning difficulties, obesity, and other conditions that echo into adolescence and adulthood, a phenomenon known as the developmental origins of health and disease. Lead author Leonardo Trasande, MD, MPP, the Jim G. Hendrick, MD, Professor of Pediatrics at NYU Grossman School of Medicine, noted that a chemical promoted as a safer replacement for phthalates and other plasticizers may affect how babies grow in the womb, and that even small shifts in birth size can carry consequences across the life course.

The study drew its data from the Environmental Influences on Child Health Outcomes program, a National Institutes of Health initiative that tracks families’ health from pregnancy through childhood. One of the strengths of this cohort is its diversity: participants came from many different racial, ethnic, and economic backgrounds across the United States, making the results more representative of the nation than those of many earlier studies, which often relied on smaller or more homogeneous samples. Urine samples were analyzed for three DINCH breakdown products, the metabolites that the body produces as it processes and excretes the chemical. Some participants provided more than one sample, which allowed the researchers to track exposure across different trimesters of pregnancy, a methodological advance that distinguishes this work from prior analyses.

Indeed, the researchers report that this is the first study to measure DINCH at different times during pregnancy, and the timing of exposure proved to be an important variable. DINCH exposure during the third trimester was more strongly tied to lower birth weight for gestational age than exposure earlier in pregnancy, a pattern that aligns with the biology of late gestation, when fetal growth accelerates rapidly and nutrient and oxygen transfer through the placenta becomes especially critical. The analysis also accounted for other factors known to influence birth size, including the mother’s age, education, and number of previous pregnancies, strengthening the case that the observed associations are not simply artifacts of confounding.

The results revealed notable patterns beyond overall weight. Babies whose mothers had higher levels of DINCH in their urine were more likely to be classified as small for gestational age, a clinical designation applied when a newborn’s weight falls below the 10th percentile for babies born at the same stage of pregnancy. Sex-specific differences emerged as well: boys showed greater differences in birth length, while girls were more likely to be small for their gestational age. Between 50 percent and 70 percent of the pregnant women in the study had measurable levels of a DINCH by-product in their urine, indicating that exposure to this substitute plasticizer is widespread in the American population rather than confined to a narrow subset of consumers.

Mechanistically, laboratory studies in animals and human cells offer clues about how DINCH might influence fetal development. These studies suggest that when DINCH breaks down in the body, its by-products can interfere with hormones that guide fetal development and trigger inflammation that may affect how nutrients and oxygen reach the baby. Together, these effects may contribute to pregnancy complications such as reduced fetal growth, high blood pressure during pregnancy, and early labor. A small analysis of pregnant women undergoing fertility treatment has also linked higher DINCH exposure to an increased chance of preterm birth, although that particular finding was not observed in the current report, leaving the question of preterm delivery open for further investigation.

The study also raised concerns about disparities in exposure and health impacts. Mothers who were Hispanic or who had lower levels of education were more likely to have children affected by DINCH, according to the authors, a pattern consistent with broader evidence that chemical exposures are not evenly distributed across the population and that communities already facing structural disadvantages may bear a disproportionate share of environmental health burdens. Trasande argued that these results underscore the need for stronger oversight of chemicals used in food packaging and other household products, requiring that they be tested before they are introduced to the market rather than after they are connected to health concerns. He pointed to the global plastics treaty now under negotiation at the United Nations as a key opportunity to establish such policies.

The researchers were careful to note an important limitation: the analysis is observational and cannot prove that DINCH exposure directly causes smaller birth size. Observational studies of this kind identify associations within large populations, and while the team controlled for many known determinants of birth size, residual confounding remains a possibility in any study of environmental exposures. Nonetheless, the convergence of human epidemiological data with laboratory evidence of endocrine interference and inflammatory effects strengthens the biological plausibility of the findings and adds DINCH to the growing list of plastic additives whose health profiles warrant reexamination.

Looking ahead, the study authors plan to examine other plasticizers currently being used as alternatives to phthalates and to study in more detail how DINCH may slow fetal growth. Senior author Taylor Etzel, PhD, of Johns Hopkins University led the work alongside Trasande, with contributions from researchers at NYU Langone, RTI International, Northeastern University, Rutgers University, Johns Hopkins, the University of Colorado Anschutz, Emory University, Columbia University, the University of Michigan, Penn State University, the University of California, San Francisco, Dartmouth College, Wayne State University, the University of Washington, the University of Illinois at Urbana Champaign, and the University of North Carolina at Chapel Hill. Funding was provided by the National Institutes of Health’s Environmental Influences on Child Health Outcomes program. In the meantime, Trasande suggested that families concerned about plastic additives can talk with their healthcare providers and consider practical steps that may reduce exposure, while the scientific and policy communities continue to evaluate whether the replacements for yesterday’s problem chemicals are solving the problem or simply relocating it.

Subject of Research: Effects of prenatal exposure to the plasticizer DINCH on fetal growth and birth outcomes

Article Title: Exposure to ‘safer’ plastic additive during pregnancy linked to smaller birth size

Article References: Exposure to ‘safer’ plastic additive during pregnancy linked to smaller birth size. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: DINCH, phthalates, plasticizers, prenatal exposure, birth weight, fetal growth, endocrine disruption, ECHO program, Environment International, NYU Langone, plastics treaty, environmental health