Table 1.

Measures

MEASURES	Description
Children’s cognitive skills
PIAT mathematics score	84 multiple-choice items. Standardized to have mean of 100 and standard deviation of 15
PIAT reading recognition score	84 words for a child to read silently, then say it aloud. Standardized to have a mean of 100 and standard deviation of 15.
Intrauterine factors
Maternal prepregnancy BMI	Calculated from self-reported adult height and weight just before each pregnancy. Categorized to underweight, normal weight, overweight, and obese according to the World Health Organization BMI categories.
Maternal gestational weight gain	Reported weight changes of mother during each pregnancy: categorized into below, within, and above recommendation using the 2009 IOM Guideline according to prepregnancy BMI categories.
Birth weight	Mother reported birth weight in kilograms.
Family background
HOME-SF cognitive stimulation score	A permanent measure constructed from HOME-SF cognitive stimulation subscale by averaging all scores of a child over entire observation window. Questions and raw scores differ by age groups (less than 3 years, ages 3 – 5, ages 6 – 9, and ages 10 – 14). Some items of the HOME-SF included: numbers of books or toys child has, how many times child gets out of house, how many times child eats meals with both parents, and if the play environment is safe.
Household income in 2008 US dollars	A permanent measure constructed from household income and number of persons in the household deflated to 2008 US dollars. It is an average of per-capita income from birth of a child to the age of his/her PIAT assessment.
Maternal factors
Education	Expressed as maximum years of education completed
Cognitive skills	Age adjusted percentile score of Armed Force Qualification Test (AFQT). Developed by the Department of Defense, and a measure of trainability and a primary criterion of enlistment eligibility for the Armed Forces. Four areas of ASVAB, arithmetic reasoning, word knowledge, paragraph comprehension, and mathematics knowledge, make up AFQT scores.
Age of mother at birth of child	Reported in years.
Child factors
Gender	Male vs. female (female=1)
Height at PIAT assessment	Height percentile for age and gender, calculated from mother reported or measured height using the CDC growth chart program.
PPVT age of child at PIAT assessment	Reported in months. Determined by the Peabody Picture Vocabulary Test score. PPVT> 60mon is the eligibility for the PIAT assessment.
Birth order	Dichotomous measure: first child =1
Race/ethnicity	Mother reported race/ethnicity: Hispanic, African American, White, and Asian.