MATERNAL THYROID FUNCTION DURING PREGNANCY, ACTA UNIVERSITATIS OULUENSIS D Medica 1092
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|Tekijät:||MÄNNISTÖ TUIJA|| |
Maternal thyroid dysfunction and/or antibodies are present in 5-10% of pregnancies and may beassociated with increased risks of adverse pregnancy and perinatal outcomes. In the present studymaternal thyroid function and antibody status in the Northern Finland Birth Cohort 1986 wasanalyzed using early pregnancy serum samples.
The impact of long-term storage on the stability of thyroid hormones and antibodies wasstudied and while TSH and thyroid hormone levels were not affected by storage time theconcentrations of thyroid antibodies appeared to be significantly increased after 10 years ofstorage. Normal maternal thyroid function was evaluated by calculating thyroid hormonereference intervals in the thyroid antibody-negative population using a biobank of stored serumsamples. Thyrotropin, free thyroxine and triiodothyronine reference intervals in the first andsecond trimester were 0.07–3.1 mU/L and 0.10–3.5 mU/L, 11.4–22.4 pmol/L and 11–18.9 pmol/L; and 3.4–7.0 pmol/L and 3.5–7.3 pmol/L, respectively, in this population (Abbott Architectmethod).
Compared with thyroid antibody-negative mothers, antibody-positive mothers hadsignificantly higher TSH and lower fT4 concentrations and an increased risk of experiencing deathof an infant in the perinatal period with odds ratios (ORs) of 3.1 (95% confidence interval 1.4–7.1)for thyroid-peroxidase and OR 2.6 (1.1–6.2) for thyroglobulin antibody positivity. These infantswere more often born very preterm, which could possibly explain these increased risks. Positivethyroid antibody status was not associated with preterm birth in this study. No other majorpregnancy or perinatal complications were observed among mothers or newborns of mothers withthyroid dysfunction/antibodies. Mothers, who had hypothyroidism or thyroid antibodies duringpregnancy, had a very high risk of subsequent thyroid disease: hazard ratio (HR) 17.7 (7.8–40.6)for overt hypothyroidism, 4.2 (2.3–7.4) for thyroid-peroxidase and 3.3 (1.9–6.0) for thyroglobulinantibody positivity. Mothers with hypothyroidism during pregnancy had increased risk ofsubsequent diabetes, (HR 6.0 [2.2–16.4]).
Women at risk of thyroid dysfunction should be recognized and their prepregnancy counseling,blood sampling and treatment is probably beneficial. Whether universal screening of all pregnantwomen is justified is still under debate.