Effects of maternal first trimester thyroid stimulant hormone levels on birth weights of fetuses born at term

Objective: We aimed to investigation the relationship between first trimester maternal thyroid stimulant hormone (TSH) levels and fetal birth weight in pregnants with TSH results within normal ranges. Methods: A total of 193 patients meeting study criteria were separated into two groups according to their TSH levels found at first trimester as those between 0.4 and 2.5 mU/L, and those between 2.5 and 4.2 mU/L. There were 162 patients in the first group (Group 1) with TSH level between 0.4 and 2.5 mU/L, and 31 patients in the second group (Group 2) with TSH level between 2.5 and 4.2 mU/L. Birth weights were also categorized under three groups which were 3500 g. These three fetal weight groups and two TSH groups established according to their first trimester measurements were compared. Results: When both groups were compared in terms of demographic data and fetal weight, there was no significant difference between two groups in terms of the parameters analyzed. In both TSH groups, distribution percentages of the patients were found statistically similar according to fetal birth weights. Conclusion: We found that normal TSH levels have no effect on fetal birth weight and that a further examination may not be required in terms of thyroid functions when TSH level is found within normal ranges at first trimester in terms of affecting fetal weight.