The Presence of Thyroid Peroxidase Antibody Is Associated with Lower Placental Weight in Maternal Thyroid Dysfunction.

Thyroid dysfunction (TD) is caused by thyroid peroxidase (TPO) antibody, as seen in Hashimoto's disease. TD is a common problem of reproductive age and may impair fetal development. Here, we determined the effect of TPO antibody on perinatal outcomes in Japanese women with TD before conception. A retrospective study involving cases of maternal TD with term singleton birth was conducted. The subjects with TD were divided into two groups according to the presence (n = 22) or absence (n = 20) of TPO antibody. The control groups matched for age, parity, and gestational weeks were selected for TPO antibody-positive (n = 44) and -negative TD subjects (n = 40), respectively. Using the standard curve of Japanese placental weight, the frequency of placental weight less than the 50th percentile (small placenta) was examined. Placental weight was lower among TPO antibody-positive TD subjects, compared with TPO antibody-negative TD subjects (p < 0.01). However, other outcomes were similar between the groups. Importantly, compared with control mothers, placental weight was significantly lower (p < 0.01), birth weight tended to be lower (p = 0.07), and the incidence of gestational diabetes mellitus was higher (p = 0.02) among TPO antibody-positive subjects. There was no significant difference in placental weight between TPO antibody-negative subjects and controls. The frequency of small placenta was significantly higher in TPO antibody-positive subjects (odds ratio: 16.7) even when considering diabetes and pregnancy induced hypertension. Thus, the presence of TPO antibody is associated with lower placental weight among Japanese women having TD.