Enfermedad tiroidea y gestaciónEvolución y resultados del embarazo según el sexo fetal y el estado tiroideo

Abstract

Maternal thyroid status influences gestational outcomes but there is limited information about the relationship in different pregnancy periods, fetal sex could be a predictive variable for gestational outcomes, as it is the case in the general population and there are some data suggesting that fetal sex could act be a modifying variable of the effect of maternal thyroid status. OBJECTIVES: In women with thyroid disfunction, to evaluate pregnancy outcomes according to maternal thyroid status in different periods of pregnancy, fetal sex and fetal sex as an effect modifier. METHODOLOGY: Retrospective analysis of women attended at the Clinic of Endocrinological Diseases and Pregnancy of Hospital de la Santa Creu i Sant Pau in the period 1986 - 2014 either due to treatment with thyroid hormone or maternal hyperthyroidism during pregnancy. Main exposure variable: maternal thyroid status in each trimester or globally during pregnancy. The association of the exposure variables and gestational outcomes was assessed with a multivariate analysis. Interaction terms of fetal sex with maternal thyroid variables were included. RESULTS: Period of hormonal disturbance. In women treated with thyroid hormone, in first trimester, subclinical hypothyroidism was associated with a lower birth weight (β -0.073, p <0.049). In third trimester, hypothyroidism was associated with low Apgar at 1st minute at the expense of clinical hypothyroidism (aOR 10.404, 95% CI 1.021-106.002) and with pregnancy-induced hypertension at the expense of subclinical hypothyroidism (aOR 4.389, 95% CI 1.471-13.099). In women followed by hyperthyroidism, clinical hyperthyroidism in the third trimester was associated with lower birth weight (β -0.235, p <0.041). Fetal sex. In women treated with thyroid hormone during pregnancy, male sex was associated with birth weight (β 0.139, p <0.001), macrosomia (aOR 2.150, 95% CI 1.020-4.532), LGA (aOR 5.782, 95% CI 1,067-31,340) and neonatal respiratory distress (aOR 0.027, 95% CI 0.002-0.348). Fetal sex as an effect modifier. In women treated with thyroid hormone, the association of first trimester subclinical hyperthyroidism with large-for-gestational-age newborns (LGA) was only observed in male newborns (aOR 8.284, 95% CI 1.952-35.157). In women followed by hyperthyroidism, the association of clinical hyperthyroidism in the third trimester with birth weight was only observed in female newborns (β -0.350, p <0.009). CONCLUSIONS: 1-The associations of the maternal thyroid status with pregnancy outcomes vary according to pregnancy period and are more apparent in the first and third trimesters. 2-In women treated with levothyroxine, male fetuses have more unfavorable pregnancy outcomes. 3-Fetal sex modifies the relationship between maternal thyroid status and pregnancy outcomes.