Prematurity, or delivery before the baby is ready to be born, is one of the most important causes of death in newborns and babies. It is also associated with major health problems later in life, leading to long term health and economic costs. Prevention of preterm delivery is difficult as the factors involved in causing premature birth are not well understood. Thyroid hormone level in the mother are very important in the growth and development of the baby, especially early in pregnancy. Thyroid hormones are also important for the normal development of the placenta, a critical component to maintain pregnancy. Research has shown that high thyroid hormone levels (hyperthyroidism) or low thyroid hormones (hypothyroidism) are associated with poor outcomes for the mother and the developing newborn. However, most studies have not followed levels during pregnancy and have only checked levels once during the first or the second trimester of pregnancy. In addition, the influence of mild thyroid dysfunction is not known. This study aimed to determine whether mild variations of thyroid function, measured four times during pregnancy, are associated with preterm delivery in women without thyroid disease.
THE FULL ARTICLE TITLE:
Johns LE et al. Longitudinal profiles of thyroid hormone parameters in pregnancy and associations with preterm birth. PLoS One 2017;12: e0169542.
SUMMARY OF THE STUDY
Women were recruited before 15 weeks of pregnancy at the Brigham and Women’s hospital in Boston. A total of 130 women who delivered babies before 37 weeks of gestation (premature deliveries) were cases and 352 women were controls. Women who had thyroid disease before or during pregnancy were excluded (41 women). Samples were collected up to four times during pregnancy, at a 10, 18, 26, and 35 weeks of gestation. TSH, active, free T4 (FT4), Total T4, and total T3 were measured. They studied the difference in the changes of thyroid-function measurements and the association of thyroid function at each time point with premature birth. The final study population included 116 patients with preterm birth and 323 controls, for which 1443 blood samples were available.