Low level lead exposure and pregnancy outcomes in an observational birth cohort study: dose–response relationships

Table 1 Associations between maternal B-Pb and birth outcomes modelled with adjusted multivariable fractional polynomial models in ALSPAC

	n	Unstandardised B regression coefficient (95 % confidence interval)	Fit in adjusted mfp model (final powers)^a
Adjusted model
Birthweight (g)	3096	−9.93 (−20.27, 0.41)	1
Head circumference (cm)	2741	−0.03 (−0.06, 0.00)	1
Crown–heel length (cm)	2706	−0.05 (−0.10, 0.00)	1
Adjusted model with exclusion of values >10 µg/dl
Birthweight (g)	3084	−11.07 (−22.12, 0.18)	1
Head circumference (cm)	2732	−0.04 (−0.07, 0.00)	1
Crown-heel length (cm)	2697	−0.06 (−0.11, 0.00)	1
Adjusted model for sensitivity analysis^b
Birthweight (g)	2785	−8.16 (−18.97, 2.65)	1
Head circumference (cm)	2466	−0.04 (−0.08, 0.01)	1
Crown–heel length (cm)	2436	−0.08 (−0.15, 0.00)	1

mfp multivariable fractional polynomial
^aAdjusted for maternal educational attainment, smoking, gestational age (centred at 40 weeks), maternal height and pre-pregnancy weight, and sex of the infant. 1, linear
^bExclusion of upper and lower 5 % of B-Pb values