Maternal Thyroid Hypofunction and Pregnancy Outcome

Abstract

OBJECTIVE-To estimate whether maternal thyroid hypofunction is associated with complications. METHODS-A total of 10,990 patients had first-and second-trimester serum assayed for thyroid-stimulating hormone (TSH), free thyroxine (freeT4), and antithyroglobulin and antithyroid peroxidase antibodies. Thyroid hypofunction was defined as 1) subclinical hypothyroidism: TSH levels above the 97.5th percentile and free T4 between the 2.5th and 97.5th percentiles or 2) hypothyroxinemia: TSH between the 2.5th and 97.5th percentiles and free T4 below the 2.5th percentile. Adverse outcomes were evaluated. Patients with thyroid hypofunction were compared with euthyroid patients (TSH and free T4 between the 2.5th and 97.5th percentiles). Patients with and without antibodies were compared. Multivariable logistic regression analysis adjusted for confounders was used. RESULTS-Subclinical hypothyroidism was documented in 2.2% (240 of 10,990) in the first and 2.2% (243 of 10,990) in the second trimester. Hypothyroxinemia was documented in 2.1% (232 of 10,990) in the first and 2.3% (247 of 10,990) in the second trimester. Subclinical hypothyroidism was not associated with adverse outcomes. In the first trimester, hypothyroxinemia was associated with preterm labor (adjusted odds ratio [aOR] 1.62; 95% confidence interval [CI] 1.00-2.62) and macrosomia (aOR 1.97; 95% CI 1.37-2.83). In the second trimester, it was associated with gestational diabetes (aOR 1.7; 95% CI 1.02-2.84). Fifteen percent (1,585 of 10,990) in the first and 14% (1,491 of 10,990) in the second trimester had antithyroid antibodies. When both antibodies were positive in either trimester, there was an increased risk for preterm premature rupture of membranes (P = .002 and P<.001, respectively).

Autoimmune Thyroid Disease in Pregnancy: A Review

“…In some studies, preterm delivery has been found to be 3-fold more common in hypothyroid pregnant women and has also been associated with an increase in spontaneous abortions, [52][53][54] although no adverse outcomes were found in a very large study of mild (subclinical) disease. 55 Another worrying danger associated with maternal hypothyroxinemia (especially when present during the first trimester) is the adverse consequences to child neuropsychointellectual development, as has been demonstrated by several studies 6,16,25,56,57 (Table 3). Whether very mild hypothyroidism has the same associations remains uncertain.…”

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

“…Furthermore, high TSH levels in women during pregnancy have been associated with an increased risk of neurocognitive deficits in the offspring (17). Other studies, however, have not found any adverse outcomes associated with SCH (18)(19)(20)(21). Moreover, there is uncertainty regarding the impact of levothyroxine replacement on improving outcomes in pregnant women with SCH (4).…”

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.…”