D around the average of the two closest measurements. For the reason that determination of gestational age by ultrasound was not obtainable for the majority of participants, duration of pregnancy was primarily based primarily around the Ballard Examination for Foetal Maturity (N = 192) (Ballard et al., 1991). This instrument estimates gestation duration by assessing physical and neuromuscular maturity. When the Ballard examination information have been not obtainable, duration of gestation was primarily based on benefits from the ultrasound performed before 15 weeks of pregnancy (N = ten) or if missing, around the date of the final menstrual period as well as a health-related exam performed by a midwife at the initial prenatal stop by (N = 28). two.five Statistical analyses two.five.1 Control variables–Pre- and postnatal maternal interviews have been carried out to assess prospective confounding variables pertaining to demographic background, pregnancy history, and foetal exposure to other toxicants, including nicotine and alcohol. Maternal height was measured by our research assistants; maternal pre-pregnancy weight was obtained from medical charts or, when missing, from maternal recall at prenatal interview. An initial screening of potential confounding variables was performed by assessing the bivariate correlation of each control variable with each and every outcome measure. Handle variables tested had been maternal age, weight, parity, maternal tobacco (quantity of cigarettes/day) and alcohol consumption (typical absolute alcohol each day in the course of pregnancy), socioeconomic status, sex of the baby, and cord blood lead concentrations. Covariates were initially retained as potential confounders if they were correlated with outcomes at p 0.20. 2.5.2 Model testing–Cord blood concentrations of ECs had been log-transformed to cut down skewness. Relationships between growth measurements and PCB 153, Hg, and HCB had been examined. Many regression models have been employed to test direct associations of PCB 153,NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptEnviron Int. Author manuscript; offered in PMC 2014 April 01.Trimethylamine N-oxide site Dallaire et al.Hippuric acid References PageHCB, and Hg on weight, length, head circumference and duration of pregnancy.PMID:24025603 Since duration of pregnancy may well be inside the causal pathway involving contaminant levels and growth outcomes, this variable was deemed as an outcome and was not adjusted for inside the many linear models of growth parameters. Every potential confounder was entered individually within the linear model for every single outcome to which it was associated, beginning with the possible confounder using the strongest association, and retained if its inclusion modified the related with the contaminant by no less than 10 . Sex from the child was included as an obligatory confounder in all predictive models of birth outcomes. Control variables retained in every single final model are presented in footnotes of Table 3. Path models have been made use of to test indirect associations of ECs and DHA on development parameters by way of their relationship with pregnancy duration. They estimate simultaneously a series of regressions with a number of dependant variables (Kline, 2010). The path model tested within this study is shown in Figure 1. Confounding variables integrated in path models have been the identical as those retained in a number of regression models. A bilateral p-value 0.05 was thought of statistically considerable. Models had been tested with the statistical package Mplus 5.21. 2.5.3 Missing Data–The proportion of missing information for the predictive and outcome variables ranged from 0 56.five . The highest numbe.