Thyroid Function in Women Found to Have Early Pregnancy Loss

Background: Pregnancy influences thyroid function and may bring to light mild and latent disorders. Thyroid dysfunction has been related to obstetrical complications such as premature delivery, gestational hypertension, preeclampsia, and placental abruption. The aim of our study was to evaluate whether the occurrence and timing of pregnancy loss could be related to thyroid autoimmunity or subclinical hypothyroidism (SH) per se.

Methods: Two hundred sixteen apparently healthy pregnant women with no previous history of thyroid disease and with diagnosis of early miscarriage (before the 12th week of gestation) were enrolled. Miscarriages were classified as very early pregnancy loss (EPL) or embryo loss (crown rump length < or =10 mm) and EPL or fetal loss (crown rump length > 10 mm). Women were subdivided into four groups: euthyroid (ET), SH, overt hypothyroidism, and thyroid autoimmunity group.

Results: One hundred seventy-six women had a normal thyroid function (84.6%), 24 patients were found to have positive thyroid antibodies (11.5%), 8 women (3.8%) an SH, and 8 cases were excluded. Thyroid-stimulating hormone levels were found to be higher in the very early (1.4 +/- 1.0 mU/L) than in the EPL group (1.1 +/- 0.7 mU/L) (p = 0.04), and in patients affected by SH (3.9 +/- 0.1 mU/L) compared to ET (1.0 +/- 0.5 mU/L) (p < 0.001) and autoimmune women (1.0 +/- 0.4 mU/L) (p < 0.001). Although the multivariate logistic regression analysis revealed that both autoimmunity and SH were independently correlated with the onset of very EPL, abortion was more precocious in the SH group (6.5 +/- 0.9 weeks), followed by the autoimmune (8.2 +/- 2.1 weeks) and ET groups (8.2 +/- 1.6 weeks) (p = 0.02).

Conclusions: Both thyroid diseases SH and autoimmune disorder are independently associated with very early embryo loss, but women suffering from SH have a lower gestational age at abortion.