Perinatal Significance of Isolated Maternal Hypothyroxinemia Identified in the First Half of Pregnancy

Abstract

Isolated maternal hypothyroxinemia has no adverse effects on perinatal outcome. Moreover, unlike subclinical hypothyroidism, there was a low prevalence of thyroid peroxidase antibodies and no correlation between TSH and free T(4) levels in women with hypothyroxinemia, leading us to question its biological significance.

11 Hypothyroidism in Pregnancy

“…Interestingly, in a very recent study by Henrichs et al [44] carried out in The Netherlands on a cohort of 3659 women, the prevalence of mild hypothyroxinemia (FT4 < 10th percentile) was 8.5% and that of severe hypothyroxinemia (FT4 < 5th percentile) 4.3%. These figures are significantly higher than those reported in previous studies conducted in iodine sufficient regions [40,42].…”

“…In another study, risks of adverse pregnancy outcomes were not increased in over 200 pregnant women with isolated hypothyroxinemia [40].…”

“…However, there are wide differences among the studies, related mainly to differences in iodine nutrition status. Indeed, in regions where iodine intake is sufficient, as is the case in the United States, the prevalence of isolated hypothyroxinemia ranges between 1.3% [40] and 2.3% [41]. In contrast, in mildly to moderately iodine deficient regions, isolated hypothyroxinemia affects a much higher percentage of women, reaching values up to 25-30% [42,43].…”

Subclinical Hypothyroidism in Pregnancy: A Systematic Review and Meta-Analysis

“…Multiple studies have reported an association of SCH with an increase in the risk of adverse pregnancy and neonatal outcomes, including pregnancy loss, preterm delivery, gestational diabetes, gestational hypertension, preeclampsia, placental abruption, premature rupture of membranes, intrauterine growth restriction, low birth weight, small for gestational age, low Apgar score, and neonatal death (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Furthermore, high TSH levels in women during pregnancy have been associated with an increased risk of neurocognitive deficits in the offspring (17).…”

Treatment of Subclinical Hypothyroidism or Hypothyroxinemia in Pregnancy

“…[8][9][10][11] However, the risks of these adverse outcomes are not increased among women with hypothyroxinemia in pregnancy. 12,13 These findings led several professional organizations to recommend routine prenatal screening for and treatment of subclinical thyroid disease during pregnancy. 14 This recommendation could affect more than 15% of pregnant women, depending on the thyrotropin and free T 4 thresholds used.…”