Poster Presentation Society of Obstetric Medicine of Australia and New Zealand ASM 2015

Subclinical Hypothyroidism in Women Undergoing In Vitro Fertilization and their Pregnancy Outcomes (#100)

Claire Felmingham 1 , Tiki Osianlis 2 , Beverley Vollenhoven 1 2 3
  1. Monash University, Melbourne
  2. Monash IVF, Melbourne
  3. Monash Medical Centre, Melbourne


Subclinical hypothyroidism (SCH), defined as a TSH between 2.5-5.0mIU/L, may cause increased rates of infertility and miscarriage. The evidence regarding this association is conflicting, and whether women with SCH should be treated with levothyroxine (LT4) leading up to and throughout pregnancy remains unclear.


To investigate whether SCH affects the clinical pregnancy and miscarriage rates following IVF, and whether treating SCH with LT4 improves these outcomes. 


We undertook a retrospective patient-matched analysis at Monash IVF, involving 59 cycles belonging to women with treated SCH, 153 cycles belonging to women with untreated SCH, and a total of 424 control cycles belonging to euthyroid women, all occurring between January 2010 and June 2014. Cycles were divided according to TSH concentration, past diagnoses of thyroid conditions, and LT4 treatment status. Overtly hypothyroid and hyperthyroid women were excluded from the study. Controls were matched to cases according to patient age, day of embryo transfer, number of eggs collected, and type of insemination. Pregnancy outcomes measured include embryo utilization rate, fertilization rate, pregnancy rate and miscarriage rate.


Embryo utilization rate improved in cycles belonging to women with treated SCH (53.50%) compared with cycles belonging to women with untreated SCH (41.20%), p=0.0002. Embryo utilization rate was also higher in cycles belonging to women with treated SCH (53.50%) when compared with their euthyroid controls (41.80%), p=0.0007. There was no difference in fertilization rate or utilization rate between the untreated SCH cycles and their euthyroid controls. There were also no statistically significant differences in pregnancy or miscarriage rate between any of the groups


This study has shown that LT4 treatment of SCH during IVF treatment may improve the embryo utilization rate, when compared with untreated SCH. However ultimately we have seen no differences in pregnancy or miscarriage rates between any of the groups. Therefore we cannot support the recommendations for LT4 treatment of women with SCH leading up to and during pregnancy.