TSH testing will be performed using the Ultrasensitive hTSH II method on an AbbottAxsym. (Abbott Diagnostics, Abbott Park, Illinois.) This is a Microparticle Enzyme Immunoassay (MEIA) method. The analytical sensitivity of the Axsym Ultrasensitive hTSH II is 0.03 uIU/mL. The intraassay coefficient of variation (CV) is 4.35% and the interassay coefficient of variation (CV) is 5.73%. A TSH greater than 2.5 μU/ml in the first trimester, or greater than 3.0 μU/ml in the second or third trimester was considered abnormal. Glinoer et al has demonstrated that 18% of women without thyroid disease have a suppressed Thyroid Stimulating Hormone (TSH) . Therefore, in our previous study TSH values below 0.3 μU/ml were not considered abnormal during pregnancy unless it occurred after the 20th week of gestation.