Analysis of changes in routine blood parameters and thyroid hormone levels in women at different stages of pregnancy and their correlations with TPOAb

Objective To investigate the patterns of changes in routine blood parameters， thyroid hormone levels， and their correlations with thyroid peroxidase antibodies （TPOAb） among women at different stages of pregnancy， so as to provide a theoretical basis for maternal and child health care and diagnosis and treatment.

Methods A total of 732 pregnant women at different stages of pregnancy who underwent health examinations at the First Maternity and Infant Hospital affiliated to Tongji University from May 2020 to August 2022 were selected as the observation group. The group comprised 245 women in the first trimester （≤12 weeks）， 247 women in the second trimester （between13 and 27 weeks） and 240 women in the third trimester （≥28 weeks）. Additionally， 240 non-pregnant， healthy women of child-bearing age who conducted their health checkups in the same hospital were selected as the control group. All the research subjects were required to provide peripheral venous blood samples to measure hemoglobin （Hb）， standard deviation of red blood cell distribution width （RDW-SD）， coefficient of variation of red blood cell distribution width （RDW-CV）， platelet （Plt） count， platelet distribution width （PDW）， as well as thyroid stimulating hormone （TSH）， total thyroxine （TT4）， total triiodothyronine （TT3）， free thyroxine （FT4）， free triiodothyronine （FT3）， and TPOAb. The results were statistically analyzed.

Results With advancing gestational age， Hb levels were significantly lower in the second and third trimesters than in the first trimester and the control group （F=68.25， P<0.001）， while RDW-SD and RDW-CV were significantly higher （F=41.34， P<0.001； F=3.64， P=0.012）. Plt levels throughout pregnancy were significantly lower than that in the control group （F=43.21， P<0.001）. TSH levels were significantly lower in the first and second trimesters than in the control group （Z=53.49， P<0.001）， but gradually increased with gestational age. TT3 and TT4 levels were significantly higher than those in the control group throughout pregnancy （F＝148.25， P<0.001； F＝210.83， P<0.001）， while FT3 and FT4 levels were significantly lower in the second and third trimesters than in the first trimester and the control group （F=42.95， P<0.001； F=101.73， P<0.001）. The abnormal rate of TPOAb was significantly higher than that in the control group throughout pregnancy （χ²＝25.61， P<0.001）. Among pregnant women， those with TPOAb positivity had significantly higher TSH levels and RDW-CV than those with TPOAb negativity （Z＝5.70， P<0.001； t＝2.39， P＝0.018）.

Conclusion The levels of Hb， Plt， and thyroid hormones in pregnant women are closely related to gestational age. With increasing gestational age， the abnormal rate of TPOAb decreases， but the TSH levels and RDW-CV of TPOAb positive pregnant women are higher， requiring clinical attention and screening to improve maternal and child health.