Background: Studies have shown that altered thyroid function in early pregnancy may affect normal placental development and hence fetal growth. Our hypothesis is that maternal thyroid function in the first trimester is altered in pregnancies that subsequently deliver small for gestational age (SGA) neonates.
Methods: Maternal serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were measured at 11(+0) to 13(+6) weeks' gestation in 212 singleton pregnancies with no history of thyroid disease that subsequently delivered SGA neonates and the values were compared with the results of 3598 normal pregnancies delivering neonates with birth weight above the 5th percentile for gestation.
Results: There were no significant differences between the normal and SGA groups in median multiple of the median (MoM) TSH (1.07 vs. 1.061 MoM), FT4 (0.992 vs. 1.010 MoM), and FT3 (0.991 vs. 0.990 MoM).
Conclusion: In women with no history of thyroid disease delivering SGA neonates, thyroid function during the first trimester of pregnancy is not significantly different from women delivering non-SGA neonates.