Fertility clinics may be exposing patients to excessive iodine during routine tests

<p>Objective: To examine factors associated with fertility following hysterosalpingography (HSG) using an oil-soluble contrast medium (OSCM).</p><p>Design: In a prospective cohort study on 196 women undergoing OSCM HSG, we showed that iodine excess was almost universal (98%) and mild subclinical hypothyroidism was frequent (38%). Here, we report the analyses of secondary outcomes examining factors associated with the likelihood of pregnancy following the HSG.</p><p>Setting: Auckland, New Zealand (2019-2021).</p><p>Sample: 196 women with primary or secondary infertility who underwent OSCM HSG.</p><p>Methods: Baseline and serial urine iodine concentrations (UIC) and thyroid function tests were measured over six months following the HSG. Pregnancy and treatment with levothyroxine during the study period were documented.</p><p>Results: Following OSCM HSG, pregnancy rates were 49% in women aged &lt;40 years (77/158) but considerably lower (16%) among those &gt;= 40 years (6/38). Similarly, live birth rates were markedly lower in women &gt;= 40 years (17%; 1/6) versus &lt;40 years (73%; 56/77). 29% of participants were iodine deficient at baseline despite advice recommending iodine fortification. Following HSG, the likelihood of pregnancy in women with moderate iodine deficiency was 64% higher than in women with normal iodine levels (p=0.048). Among women aged &lt;40 years who had subclinical hypothyroidism (n=75), levothyroxine treatment was associated with higher pregnancy rates compared to untreated women [63% (26/48) vs 37% (10/27), respectively; p=0.047].</p><p>Conclusion: OSCM HSG was associated with higher pregnancy rates in women &lt;= 40 than in those aged &gt;40 years. Iodine deficiency was relatively common in this cohort, and increased iodine levels from OSCM exposure may contribute to the improved fertility observed with this procedure.</p>