Impact of subclinical hypothyroidism in women with recurrent early pregnancy loss.

OBJECTIVE: To assess the impact of subclinical hypothyroidism (SCH) in women with recurrent early pregnancy loss (REPL).

DESIGN: Observational cohort study.

SETTING: REPL program in an academic medical center.

PATIENT(S): 286 women with a history of ≥2 pregnancy losses <10 weeks.

INTERVENTION(S): From 2004-2007, no treatment for women with SCH (thyroid-stimulating hormone [TSH] >2.5 mIU/L with a normal free thyroxine or free thyroxine index); from 2008 onward, levothyroxine treatment prepregnancy to maintain TSH ≤2.5 mIU/L.

MAIN OUTCOME MEASURE(S): Live-birth rate (LBR).

RESULT(S): The prevalence of SCH was 55 (19%) of 286 in this REPL cohort. The cumulative LBR was 27 (69%) of 39 for women with SCH versus 104 (74%) of 141 for euthyroid women. The per-pregnancy LBR was 34 (49%) of 69 for SCH versus 129 (58%) of 221 for euthyroid women. When the LBR was compared between treated and untreated SCH, the cumulative LBR was 17 (71%) of 24 versus 10 (67%) of 15, respectively. The per-pregnancy LBR for SCH treated versus untreated women was 22 (48%) of 46 versus 12 (52%) of 23, respectively.

CONCLUSION(S): Although there was a high prevalence of SCH in the REPL cohort, there was no statistically significant difference in the subsequent live-birth rate when comparing women with SCH and euthyroid women, or treated and untreated SCH.