Thyroid stimulating hormone (TSH) level variations in early pregnancy and feto-maternal outcome; retrospective study

Abstract

Introduction: Thyroid disease is the second most common endocrine disorder affecting women of reproductive age. The debate continues which TSH levels need to be considered as a reflection of subclinical hypothyroidism in pregnancy. Our aim was to find out if variations in the level of thyroid stimulating hormone (TSH) in early pregnancy of women not known to have thyroid disease or anti-thyroid antibodies were linked to different fetomaternal outcomes. Materials and Methods: Retrospective comparative study that compared group 1 (TSH level 0.1-1.99 mIU/L) and group 2 (TSH level 2.0-4 mIU/L). Each group was further subdivided into primigravidae and multipara with a total of 1527 pregnant women included in the study. Results: The body mass index (BMI), was statistically higher in primiparous women in group 2 (P2) than primiparous in group 1 (P1), (mean BMI 28.0 vs. 26.9, respectively, P value 0.014). The odds ratio of miscarriage in the primigravidae in group 2 was 1.24. This was not statistically significant (95% confidence interval; 0.42-3.63). The miscarriage rate was not also statistically different between multipara (odds ratio 1.04, 95% CI 0.6-1.7). For the primigravid groups, the odds of developing gestational diabetes mellitus was significantly higher in group 2 than in group 1 (Odds Ratio = 2.6, 95% CI 1.2-5.4). This was not seen in multiparous women. This difference could be explained by the higher BMI in group 2. There was a significant difference in the mean arterial blood pressure in multipara between the 2 groups. Although the values of the mean blood pressure (85 and 84 mmHg) were close, the P-value of the t-test performed was 0.007 possibly due to the difference in variance and sample size of each group. There were no statistical difference in the mean gestational age at delivery, preterm birth, mode of delivery and birth weight of term and preterm deliveries. Conclusions: In singleton pregnancies of women without thyroid dysfunction and with negative anti-thyroid antibodies, variations of the TSH level in early pregnancy up to 4.0 mIU/L were not associated with a significant difference in most of the fetomaternal outcomes. TSH values between 2.0-4.0 mIU/L were found to be associated with gestational diabetes in primigravid women and higher mean arterial blood pressure in multiparous women.