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J Clin Endocrinol Metab. 2010 Sep;95(9):E44-8. doi: 10.1210/jc.2010-0340. Epub 2010 Jun 9.

Increased pregnancy loss rate in thyroid antibody negative women with TSH levels between 2.5 and 5.0 in the first trimester of pregnancy.

Author information

1
Division of Endocrinology, V. Fazzi Hospital, 73100 Lecce, Italy. dr.negro@libero.it.

Abstract

CONTEXT:

The definition of what constitutes a normal TSH during pregnancy is in flux. Recent studies suggested that the first trimester upper limit of normal for TSH should be 2.5 mIU/liter.

OBJECTIVE:

The objective of the study was to evaluate the pregnancy loss and preterm delivery rate in first-trimester thyroid peroxidase antibody-negative women with TSH values between 2.5 and 5.0 mIU/liter.

DESIGN:

The present study is a component of a recently published large-scale prospective trial that evaluated the impact of levothyroxine treatment on maternal and neonatal complications in thyroid peroxidase-positive women with TSH levels above 2.5 mIU/liter. The present study evaluated 4123 thyroid peroxidase antibody-negative women with TSH levels at or below 5.0 mIU/liter. Women were divided into two groups based on their initial TSH: group A, TSH level below 2.5 mIU/liter, excluding hyperthyroid women defined as an undetectable TSH with an elevated free T(4), and group B, TSH level between 2.5 and 5.0 mIU/liter.

SETTING:

The study was conducted at two ambulatory clinics of community hospitals in southern Italy.

PATIENTS:

A total of 4123 women were evaluated.

INTERVENTION:

There was no intervention.

MAIN OUTCOME MEASURES:

The incidence of pregnancy loss and preterm delivery in group A as compared with group B was measured.

RESULTS:

The rate of pregnancy loss was significantly higher in group B as compared with group A (6.1 vs. 3.6% respectively, P = 0.006). There was no difference in the rate of preterm delivery between the two groups.

CONCLUSIONS:

The increased incidence of pregnancy loss in pregnant women with TSH levels between 2.5 and 5.0 mIU/liter provides strong physiological evidence to support redefining the TSH upper limit of normal in the first trimester to 2.5 mIU/liter.

PMID:
20534758
DOI:
10.1210/jc.2010-0340
[Indexed for MEDLINE]

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