MONDAY, June 22, 2026 (HealthDay News) -- Many pregnancies are exposed to environmental chemicals, some of which are associated with differences in gestational age at birth and birth weight-for-gestational age (BW-GA) z scores, according to a study published online June 17 in JAMA Network Open.Jessie P. Buckley, Ph.D., M.P.H., from the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill, and colleagues examined associations of gestational exposure to chemicals in a large diverse U.S. cohort involving 5,318 mother-child pairs. Concentrations of 113 analytes from 10 chemical classes were measured simultaneously in single, midgestation urine samples.The researchers found that 43 analytes (38 percent) were detected in 50 percent or more of samples. There was an association seen for multiple phthalates or alternative plasticizers with younger gestational age at birth or lower BW-GA z scores; for example, there was an association for summed diisononyl phthalate metabolites with a 0.6-day younger gestational age (preterm birth odds ratio, 1.16; 95 percent confidence interval, 1.01 to 1.34) and for summed phthalate or alternative plasticizers with a 0.06 lower BW-GA z score (small for gestational age odds ratio, 1.09; 95 percent confidence interval, 0.93 to 1.27). Lower BW-GA z scores were seen in association with two halogenated phenols, benzophenone 8, bisphenol F, and several polycyclic aromatic hydrocarbons; for example, an association was seen for 1- and 9-hydroxphenanthrene with a 0.04 lower BW-GA z score (small for gestational age odds ratio, 1.13; 95 percent confidence interval, 1.01 to 1.27)."Our study, along with other similar findings, underscores the importance of reducing chemical exposures that impact pregnancy, as even small changes in birth weight or gestational age can have significant impacts on children's health," Buckley said in a statement.One author disclosed receiving expert witness fees; a second author received personal fees from Linus BioTechnology.Abstract/Full Text.Sign up for our weekly HealthDay newsletter