Biomarker analysis of Fraction-1 from unexposed women. Serum samples from unexposed pregnant (n = 30) (purple bars) and non-pregnant (n = 60) (blue bars) women were separated on HPLC, followed by E-Screen analysis of the reconstituted Fr-1 (0–5.5 minutes). For samples from pregnant women, subfractions s4 (1.8–2.3 minutes) and s8 (3.8–4.3 minutes) was removed before E-Screen analysis. Results are expressed as the relative proliferative effect (RPE) to E2. Values shown are mean ± SD from triplicate wells. The broken line represents the mean background of the experimental series (the mean of negative controls + 3x SD).