sentence: For PeCDF , PCB-126 , and PCB-169 , the differences in their geometric means , expressed as a percent [ 95 % confidence interval ( CI ) ] were 1.1 % ( – 6.8 to 9.7 ) , 12.2 % ( 4.1 to 20.9 ) , and 6.8 % ( – 0.3 to 14.4 ) , respectively ; their intraclass correlation coefficients between the measurements of 2001 and 2002 were 0.98 , 0.85 , and 0.94 , respectively.The concentration of the chemical at the time of pregnancy was estimated as the concentration at sampling × 2 .