Table 1.

Characteristics of Project Viva mother–infant pairs with umbilical cord blood and midchildhood blood methylation measurement.

Characteristic	Birth ($n=268$)	Midchildhood ($n=240$)
Maternal
Prepregnancy BMI, ${\mathrm{kg}/\mathrm{m}}^2$: Mean (SD)	24.2 (5.0)	24.5 (4.9)
Age at enrollment, years: Mean (SD)	31.9 (4.7)	32.1 (5.3)
Nulliparous: $n$ (%)	131 (48.9)	113 (47.1)
College graduate: $n$ (%)	185 (69.0)	169 (70.4)
Smoking status: $n$ (%)
Never	178 (66.4)	168 (70.0)
Former	55 (20.5)	47 (19.6)
During pregnancy	35 (13.1)	25 (10.4)
Maternal white race/ethnicity: $n$ (%)	212 (79.1)	173 (72.1)
2nd-trimester Pb, $\mathrm{\mu }\mathrm{g}/\text{dL}$: Mean (SD)	1.22 (0.63)	1.20 (0.53)
Child
Female: $n$ (%)	138 (51.5)	121 (50.4)
Gestational age at birth, wk: Mean (SD)	39.7 (1.6)	39.5 (1.7)
Age at blood collection, years: Mean (SD)	–	7.9 (0.8)

Note: BMI, body mass index; Pb, lead; SD, standard deviation.