Bornehag CG, et al. - Researchers evaluated how prenatal phthalate exposure relates with language development in children in two population-based pregnancy cohort studies. Findings suggested a statistically significant association of prenatal exposure to dibutyl phthalate and butyl benzyl phthalate with language delay in children in both the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study and The Infant Development and the Environment Study (TIDES).

Methods

• Experts obtained the data for this study from the SELMA study conducted in prenatal clinics throughout Värmland county in Sweden and TIDES conducted in four academic centers in the US.
• Participants in both studies were women in their first trimester of pregnancy who had literacy in Swedish (SELMA) or English or Spanish (TIDES).
• They included mothers and their children from both the SELMA study (n = 963) and TIDES (n = 370) who had complete data on prenatal urinary phthalate metabolite levels, language delay, and modeled covariables.
• They collected data from November 1, 2007 to June 30, 2013, and conducted data analysis from November 1, 2016, to June 30, 2018 for SELMA; data collection for TIDES began in January 1, 2010 and ended in March 29, 2016, and data analysis was performed from September 15, 2016 to June 30, 2018.
• A language development questionnaire that asked the number of words their children could understand or use at a median of 30 months of age (SELMA) and 37 months of age (TIDES) were completed by mothers.
• They categorized the responses as fewer than 25, 25 to 50, and more than 50 words, with 50 words or fewer classified as language delay.

Results

• As per data, 963 mothers, 455 (47.2%) girls, and 508 [52.8%] boys were included from the SELMA study, while 370 mothers, 185 (50.0%) girls, and 185 (50.0%) boys were included from TIDES.
• In both SELMA (96 reported) and TIDES (37 reported), the prevalence of language delay was 10.0%, with higher rates of delay in boys than girls (SELMA: 69 [13.5%] vs 27 [6.0%]; TIDES: 12 [12.4%] vs 14 [7.6%]).
• In crude analyses, they noted statistically significant association of the metabolite levels of dibutyl phthalate and butyl benzyl phthalate with language delay in both cohorts.
• Results demonstrated that in adjusted analyses, a doubling of prenatal exposure of dibutyl phthalate and butyl benzyl phthalate metabolites increased the odds ratio (OR) for language delay by approximately 25% to 40%, with statistically significant results in the SELMA study (dibutyl phthalate OR, 1.29 [95% CI, 1.03-1.63;P=.03]; butyl benzyl phthalate OR, 1.26 [95% CI, 1.07-1.49;P=.003]).
• Findings suggested an association of a doubling of prenatal monoethyl phthalate exposure with an approximately 15% increase in the OR for language delay in the SELMA study (OR, 1.14; 95% CI, 1.00-1.31; P=.05), but no such association was found in TIDES (OR, 0.98; 95% CI, 0.79-1.23).