Previous studies have reported that during pregnancy, maternal subclinical hypothyroidism (elevated TSH with normal FT4) as well as isolated hypothyroxinemia (decreased FT4 with normal TSH) are associated with adverse maternal and child outcomes, including preterm delivery and low birth weight. However, most studies have not determined maternal thyroid hormone levels in different trimesters….mdedge.com, Preschool boys’ behaviors traced back to moms’ thyroid hormones, 2022
Researchers recruited pregnant women going for their first antenatal checkup at the Ma’anshan Maternal and Child Health Hospital in China from May 2013 to September 2014 and identified 1,860 mother-child pairs.
They determined maternal thyroid hormone levels from blood samples taken during the first, second, and third trimester: on average, gestational week 10, 25, and 34, respectively.
The researchers found that TSH levels increased somewhat from trimester 1 to trimester 2 and then decreased slightly in trimester 3. Most women (68%) had a low TSH trajectory, 28% had a moderate TSH trajectory, and 4% had a high TSH trajectory.
FT4 levels dropped sharply from trimester 1 to trimester 2 and then increased somewhat in trimester 3. About half of the women (52%) had a moderate FT4 trajectory, 33% had a low FT4 trajectory, and 15% had a high FT4 trajectory.
Most women (96.5%) had a low and stable TPOAb level, and the rest (3.5%) had high and decreasing TPOAb levels.