200 Chapter 9 predefined definition of intravasation or oil emboli and therefore 44 of the 48 studies had to be classified as ‘high risk of bias’ regarding the measurement of the occurrence of intravasation. Thyroid (dys) function We’ve noted that the maternal and foetal thyroid function after HSG is receiving more attention in the past years, both in literature and in clinical practice. The iodine content in oil-based contrast is 480IU/l, while the iodine content of the various types of water-based contrast that are used for HSG ranges from 270-320IU/l. Additionally, oil-based contrast resorbs at a much slower rate than water-based contrast meaning that the exposure to excess iodine is much longer when oil-based contrast is used (18). Iodine affects the thyroid gland and both cases of hyperthyroidism and hypothyroidism following the use of iodinated contrast have been described, the latter being more common. Thyroid abnormalities post-HSG are most prevalent in women displaying subclinical hyperthyroidism or subclinical hypothyroidism prior to HSG (7). A recent prospective cohort study showed that 38% of the 188 previously euthyroid women developed subclinical hypothyroidism in the weeks after an HSG with oil-based contrast, and nearly all (98%) women showed iodine excess as defined by urinary iodine contents (19). The mean dosage of oil-based contrast was 6.2ml (standard deviation 2.6), a relation between the dosage and thyroid function post-HSG was unfortunately not described in the paper. An older study describes the occurrence of hypothyroidism in 22.5% of the 31 women one month after an HSG with oil-based contrast, versus 9.5% of the 42 women one month after an HSG with water-based contrast (20). In the study by Mathews et al the TSH levels dropped back to normal around 12-16 weeks on average. These studies underline the importance of a comparison in thyroid abnormalities after an HSG with oil-based contrast versus water-based contrast. Additionally, as the authors conclude, the effect of temporary thyroid dysfunction on pregnancy chances and foetal development should be analysed further. A foetus is dependent on its mothers thyroid hormones for development during the first trimester, the foetal thyroid gland starts endogenous thyroid hormone production around week 16 (21). Intra-uterine deprivation of thyroid hormone impairs foetal neurological development (22). Persistent maternal iodine excess could potentially lead to congenital hypo- or hyperthyroidism in the neonate, although retrospective analysis of infants born to mothers participating in the H2Oil study showed no thyroid abnormalities in the heel-prick screening of the neonates (9, 23). Despite these reassuring results, it is still possible that these infants experienced temporary hypo- or hyperthyroidism in utero with unknown sequelae.
RkJQdWJsaXNoZXIy MTk4NDMw