Associations of gestational phthalate exposure and non-nutritive suck among infants from the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) birth cohort study

Abstract

Background: Infant non-nutritive suck (NNS), or sucking on a pacifier with no nutrients being delivered, has been used as in index of brain function and has been linked to subsequent neurodevelopment. Yet, no data are available connecting NNS to environmental exposures in utero. The goal of this study was to examine the relationship between gestational exposure to phthalates (a group of chemicals found in personal care products, PVC plastics, and other products) and NNS among infants in a birth cohort study in Puerto Rico. Methods: Urinary phthalate metabolite levels were measured in women at up to three time points in pregnancy as a measure of in utero exposure to the child. We calculated the geometric mean of each metabolite for each woman as a measure of exposure across gestation. Infants had their NNS sampled using our custom research pacifier between 4–6 (± 2 weeks) weeks of age, yielding the following NNS dependent measures: cycles/burst, frequency, amplitude, bursts/min, and cycles/min. Results: Two hundred and eight mother-infant dyads completed this study We used multiple linear regression to assess associations between individual phthalate metabolites and NNS measurements, adjusting for infant sex, birthweight, and urinary specific gravity. An interquartile range (IQR) increase in mono carboxyisononyl phthalate across pregnancy was associated with 3.5% (95%CI: −6.2, −0.8%) lower NNS frequency and 8.9% (0.6, 17.3%) higher NNS amplitude. Similarly, an IQR increase in mono-2-ethylhexyl phthalate was also associated with 3.4% (−6.5, −0.2%) lower NNS frequency, while an IQR increase in di-2-ethylhexyl terephthalate metabolites was associated with 11.2% (2.9, 19.5%) higher NNS amplitude. Gestational exposure to phthalates may alter NNS amplitude and frequency in full-term infants. These findings indicate that the infants may be increasing their NNS amplitude to compensate for their slower NNS frequency. These preliminary findings could have important clinical implications for earlier detection of exposure-related deficits in neurofunction as well as implications for subsequent neurodevelopment and related interventions.

Gestational Exposure to Phthalates and Phthalate Replacements in Relation to Neurodevelopmental Delays in Early Childhood

“…More children had communication domain DQ scores 2SD below the population mean (n = 21, 17%) in the 24 months sample compared to the other time points ( Supplementary Figure S2 ). Most measured phthalate metabolites were detected in greater than 80 % of prenatal urine samples as previously reported [ 37 , 38 ]. The distributions of maternal urinary phthalate metabolite levels over the gestation are presented in Supplementary Figure S1 and Supplementary Table S3 .…”

Non-nutritive suck as a window into infant development: unraveling the implications of non-nutritive suck through the understanding of 1) typical non-nutritive suck patterning, 2) variations across populations (cleft lip and palate), and 3) connections to neurodevelopmental outcomes

“…data underlying the findings are available in S1 Dataset. The correlations within the NNS variables were consistent with previously reported associations (78,102). For instance, NNS cycles/burst and duration are highly correlated, but are both included in the analysis as some clinical sites may only count the number of cycles within a burst and others may count the duration of the burst.…”

Impact of intrapartum oxytocin administration on neonatal sucking behavior and breastfeeding

“…Previous studies have investigated the association between NNS and fetal exposure to substances other than oxytocin. Zimmerman et al 35 examined the association between phthalate exposure during pregnancy and NNS. They reported a lower sucking frequency and higher amplitude in the exposed group of infants.…”