Preconception TSH linked to adverse maternal outcomes
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In a large cohort of Chinese women, preconception thyroid-stimulating hormone levels were linked to maternal outcomes, including preterm delivery, low birth weight and large for gestational age birth weight, according to study results.
Hanze Du, MD, PhD, of the Chinese Academy of Medical Sciences in Beijing, and colleagues wrote that few studies exist on the relationship between maternal preconception thyroid function and pregnancy outcomes, and the results remain controversial.
“The safe range of preconception TSH is still unclear,” the researchers wrote.
The researchers analyzed data from the prospective population-based study National Free Preconception Checkups Project involving 175,112 Chinese women from 30 provinces who became pregnant after enrollment, between 2010 and 2012. Researchers collected and assessed maternal TSH level within 6 months before pregnancy, along with different pregnancy outcomes.
Mean maternal age at delivery was 25.3 years, and median TSH level was 1.85 mIU/L within 6 months before pregnancy.
Data indicated a J-shaped association between TSH and large for gestational age birth weight (P < .001). Lower TSH yielded an increased OR for low birth weight (P = .003) and preterm delivery (P < .001) when TSH was lower than 1.27 mIU/L or 0.91 mIU/L.
Researchers did not observe a significant association between preconception TSH and small for gestational age birth weight, macrosomia, fetal anomalies, stillbirth, natural or induced abortion, or cesarean delivery. They did find that the TSH range for OR lower than 1 was within 0.91 mIU/L to 1.82 mIU/L in a dose-response association.
In addition, women with low TSH levels (< 0.4 mIU/L and 0.4-0.9 mIU/L) and high TSH levels (1.83-2.49 mIU/L, 2.5-3.99 mIU/L and > 4 mIU/L) were at increased risk for preterm delivery and large for gestational age infants compared with women with levels of 0.91 mIU/L to 1.82 mIU/L. No significant association was found with TSH groups and the risk for low birth weight, except for those with TSH levels less than 0.4 mIU/L.
“Preconception TSH was associated with various adverse maternal outcomes, including preterm delivery, large for gestational age and low birth weight,” Du and colleagues concluded. “Preconception TSH had a bidirectional effect on large for gestational age, and there might exist a new influence mechanism of TSH on birth weight. TSH within 0.91 mIU/L to 1.82 mIU/L was the potential safe range for preconception women.”
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