Increased Miscarriage Rate in Thyroid Antibody-negative Women with TSH Levels between 2.5-5.0 in the First Trimester of Pregnancy
From ENDO 2010 The Endocrine Society Annual Meeting, San Diego, June 19-22, 2010
Studies over the last two decades have demonstrated an increased miscarriage rate in euthyroid women who are thyroid antibody positive. Similarly, women with overt hypothyroidism have an increased rate of spontaneous pregnancy loss. The impact on pregnancy loss with thyroid-stimulating hormone (TSH) levels between 2.5-5.0 in thyroid antibody negative women is unknown. The present abstract is a component of a larger study in southern Italy in which 4562 women were screened for TSH and thyroid peroxidase (TPO) in the first trimester of pregnancy. Women were randomly assigned to a universal screening (US) group or a case finding (CF) group and stratified as high risk or low risk for thyroid disease. All women in the US group and high-risk women in the CF group had TSH and thyroid peroxidase antibody performed immediately. Women in the CF low-risk group had their sera assayed postpartum. Antibody-positive women with a TSH >2.5 were treated with levothyroxine. The results on pregnancy outcome are in press.1 The present study evaluated the miscarriage rate in thyroid antibody negative pregnant women with TSH levels between 2.5-5.0 as compared to thyroid antibody-negative women with TSH levels <2.5. None of these women were treated with levothyroxine. In the first trimester of pregnancy 4123 women were TPO negative with a TSH of <5.0 (mean time of screening was 8.8 weeks). The rate of spontaneous pregnancy loss was 6.1% (39/642) in women with a TSH between 2.5-5.0 and 3.6% (127/3481) in women with a TSH <2.5 (p=0.006).
This study demonstrated a significant increase in the rate of spontaneous pregnancy loss in antibody-negative women who have first trimester TSH levels between 2.5-5.0 as compared to antibody-negative women with first trimester TSH levels <2.5. These data provide further evidence that the normal range for women in the first trimester of pregnancy is <2.5. Future studies are needed to evaluate the impact on the miscarriage rate of levothyroxine treatment in antibody-negative women with TSH between 2.5-5.0 in the first trimester of pregnancy.
Negro R, Schwartz A, Gismondi R, et al. George Washington University, Washington, DC, USA; University of Illinois-Chicago, Chicago, Illinois, USA; Casa di Cura "Salus" Brindisi, Italy; "V Fazzi" Hospital, Lecce, Italy
These data implied that in pregnancy "compensated hypothyroidism" in thyroid antibody-negative euthyroid women may not be well compensated. Approximately 1-2% of pregnant women receive levothyroxine treatment for overt hypothyroidism. This condition, which commonly has an autoimmune cause, is defined as a low plasma free thyroxine (T4) concentration and a raised plasma TSH concentration. Another 2.5% of pregnant women have subclinical (compensated) hypothyroidism, which is defined as a raised plasma TSH concentration with a normal free T4 concentration.2 It has been suggested that in hypothyroid women anticipating pregnancy (with serum TSH in the lower quartile of normal range) pre-conception adjustment of levothyroxine doses may result in adequate maternal thyroid function.3 This procedure seems safe and inexpensive; it may be a worthwhile treatment, not only to prevent miscarriage but also in view of the well-known potential effects of even marginal maternal hypothyroid function on the subsequent IQ of the progeny.The data also suggest a role for universal screening in all newly pregnant women with testing for serum TPO antibodies and TSH levels.4
Fima Lifshitz, MD
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