Maternal iron metabolism gene variants modify umbilical cord blood lead levels by gene-environment interaction: a birth cohort study

Table 1 Characteristics of mother-infant pairs from Ottawa County, OK, stratified by availability of genotype information ^a

Characteristic	Complete genotype information		Unavailable genotype information
Characteristic	n = 476	Descriptive measure^b	n = 232	Descriptive measure^b
Mothers
Age at birth of infant (years)	476	24.5 (5.5)	228	24.6 (5.2)
Race/Ethnicity^c
White	341	70%	185	79%
Native American	120	25%	65	28%
Hispanic	24	5%	4	1.7%
Asian	16	3.3%	3	1.3%
African American	4	0.8%	1	0.4%
Education
< 12th grade	118	25%	66	28%
≥ 12th grade	358	75%	166	72%
Hematocrit at delivery (%)	468	34.3 (3.8)	225	34 (3.4)
Hematocrit at 28 weeks gestation (%)	409	35.5 (3.4)	197	34.9 (3.3)
Blood lead at delivery (μg/dL)^d	476	0.61 (1.87)	183	0.54 (1.7)
Infants
Gender (% female)	475	45%	230	48%
Gestational age (weeks)	473	39.2 (1.3)	229	38.8 (1.5)
Birth weight (g)	476	3385 (485)	229	3300 (438)
Birth length (cm)	464	49.8 (3)	227	50.4 (2.4)
Birth head circumference (cm)	458	34.7 (2.3)	225	34.3 (2)
Hematocrit at birth (%)	132	55.2 (7.8)	225	55.9 (7.2)
Serum ferritin at birth (ng/mL)	244	154 (92)	177	156 (97)
Umbilical cord blood lead (μg/dL)^d	476	0.42 (2.12)	180	0.38 (1.8)

^aComplete data are missing for certain characteristics; ^bArithmetic mean ± SD or% as indicated; ^cOverlap between categories exists because individuals could self-identify as belonging to two or more races; ^dGeometric mean ± GSD.

ISSN: 1476-069X