Association between isolated hypothyroxinaemia in early pregnancy and perinatal outcomes

Background: The effect of isolated maternal hypothyroxinaemia (IMH) on pregnancy complications and neonatal outcomes in human beings is still controversial. Methods: This was a retrospective cohort study based on the electronic medical register system. The records of women with a singleton pregnancy who sought antenatal examination between January 2014 and December 2015 at Shanghai First Maternity and Infant Hospital were extracted from the electronic medical records system. Thyroid-stimulating hormone (TSH), free thyroxine (fT4) and anti-thyroperoxidase autoantibody (TPO-Ab) was measured before 20 gestational weeks, and a multiple logistic regression model was used to estimate the odds ratios of pregnancy complications and neonatal outcomes between euthyroid women and those with isolated hypothyroxinaemia. Results: A total of 8173 women were included in this study, of whom 34 2 (4.18%) were diagnosed with IMH. Regression analysis showed that IMH diagnosed in the second trimester (13-20 weeks) was associated with an increased risk of hypertensive disorders of pregnancy (OR = 2.66, 95% CI: 1.38-5.10) and placenta abruption (OR = 3.64, 95% CI: 1.07-12.41), but not with preterm delivery (OR = 1.09, 95% CI: 0.50-2.40), small or large gestational age of infant (OR = 0.91, 95% CI: 0.39-2.12; OR = 1.16, 95% CI: 0.72-1.86), macrosomia (OR = 1.71, 95% CI: 0.95-3.07), gestational diabetes mellitus (OR = 1.36, 95% CI: 0.86-2.15) and placenta previa (OR = 1.62, 95% CI: 0.39-7.37). Conclusion: IMH could be a risk factor for hypertensive disorders of pregnancy.