Table 3.

Associations between serum PFOA and PFOS and preterm birth (< 37 weeks).

PFC metric	Crude OR All births n= 1,628 (158 cases)	AdjustedaOR (95% CI) All births n = 1,628 (158 cases)	AdjustedaOR (95% CI) First prospectivebn = 783 (73 cases)
PFOA
Per in unit increase	0.95	0.93 (0.78, 1.10)	1.09 (0.86, 1.37)
Per IQR increasec	0.96	0.95 (0.88, 1.04)	1.01 (0.92, 1.10)
Quintile (ng/mL)		p-trend= 0.629	p-trend= 0.409
0 to < 6.9	1.0 (reference)	1.0 (reference)	1.0 (reference)
6.9 to < 11.1	1.69	1.56 (0.88, 2.76)	1.11 (0.42, 2.89)
11.1 to < 18.9	1.26	1.19 (0.66, 2.14)	1.30 (0.51, 3.27)
18.9 to < 37.2	1.32	1.21 (0.67, 2.19)	1.49 (0.62, 3.61)
≥ 37.2	1.13	1.01 (0.55, 1.86)	1.32 (0.53, 3.32)
PFOS
Per in unit increase	1.04	1.02 (0.78, 1.35)	1.02 (0.72, 1.45)
Per IQR increasec	1.03	1.03 (0.83, 1.27)	0.95 (0.73, 1.25)
Quintile (ng/mL)		p-trend= 0.976	p-trend = 0.818
0 to < 8.6	1.0 (reference)	1.0 (reference)	1.0 (reference)
8.6 to < 12.1	1.21	1.11 (0.63, 1.94)	1.07 (0.44, 2.59)
12.1 to < 15.9	0.82	0.76 (0.42, 1.36)	0.63 (0.25, 1.59)
15.9 to < 21.4	1.09	1.00 (0.56, 1.78)	1.08 (0.47, 2.46)
≥ 21.4	1.09	1.07 (0.58, 1.95)	0.86 (0.36, 2.04)
aAdjusted for maternal age (cubic terms), educational level (< 12 years, 12, 13–15, ≥ 16), smoking status (current, former, non), parity (0, ≥ 1), BMI (underweight, normal, overweight, obese), self-reported diabetes, time between conception and serum measurement (year strata). bFirst pregnancy conceived after serum measurement among nonpregnant women. cUntransformed, IQR PFOS = 10 ng/mL, IQR PFOA = 22 ng/mL.