Table 3.

Study I: PFOA and pregnancy outcome based on birth records: association of PFOA with preterm birth, Mid-Ohio Valley, 1990–2004.

< 37 weeks gestation					< 32 weeks gestation
Estimated PFOA	Term births (n)	Cases (n)	Crude OR	Adjusteda OR (95% CI)	Cases (n)	Crude OR	Adjusteda OR (95% CI)
IQR(lnPFOA)b increase		3,695		3,613		0.99		1.02 (0.96, 1.08)		491		0.95		0.98 (0.86, 1.11)
100-ng/mL increase		3,695		3,613		1.01		1.02 (0.94, 1.10)		491		0.88		0.90 (0.74, 1.10)
< 40th percentile (1.0 to < 6.1 ng/mLc)		1,460		1,467		1.0		1.0		197		1.0		1.0
40th to < 60th percentile (6.1 to < 10.2 ng/mL)		755		720		1.0		1.0 (0.8, 1.1)		108		1.0		1.0 (0.7, 1.4)
60th to < 80th percentile (10.2 to < 21.0 ng/mL)		733		714		1.0		1.0 (0.9, 1.2)		95		1.0		1.1 (0.8, 1.4)
≥ 80th percentile (21.0 to 717.6 ng/mL)		747		712		1.0		1.0 (0.9, 1.2)		91		0.9		1.0 (0.7, 1.3)
aAdjusted for maternal age, education, parity, smoking status, exposure year, state of residence. bEffect estimates represent the change in outcome for a shift from the 25th percentile to the 75th percentile in estimated PFOA serum levels [IQR(lnPFOA) = 1.50]. cThe category boundaries are from the first imputed data set.