Thyroid autoimmunity and abortion: a prospective study in women undergoing in vitro fertilization.

OBJECTIVE

To determine whether an association exists between the presence of thyroid peroxidase (TPO) antibodies before pregnancy and miscarriage in women without a history of habitual abortion.

DESIGN

Prospective study and nested case-control study.

SETTING

Inner-city teaching hospital.

PATIENT(S): Four hundred eighty-nine women in an IVF program.

INTERVENTION(S): In the prospective study, we measured levels of TPO antibodies and TSH. In the nested case-control study, we also measured levels of anticardiolipin antibodies.

MAIN OUTCOME MEASURE: Miscarriage.

RESULT(S): One hundred seventy-three women were observed, of whom 31% (54/173) became pregnant. Pregnancy occurred in 48% (12/25) of the antibody-positive women and in 28% (42/148) of the antibody-negative women. Among those who became pregnant, miscarriage occurred in 33% (4/12) of TPO antibody-positive women and in 19% (8/42) of TPO antibody-negative women. The TSH level was abnormal (<0.2 microIU/mL) in only one of the TPO antibody-positive women who miscarried. The presence of anticardiolipin antibodies was not associated with miscarriage.

CONCLUSION(S): No association was found between the presence of TPO antibodies before pregnancy and miscarriage in women without a history of habitual abortion. The presence of TPO antibodies did not adversely affect a woman's chances of becoming pregnant.