December 21, 2018
2 min read

Levothyroxine improves pregnancy outcomes in women with hypothyroidism

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Levothyroxine treatment for pregnant women with hypothyroidism can reduce pregnancy and perinatal complications, such as gestational hypertension, preeclampsia and early and late preterm births, according to findings published in Thyroid.

“Untreated hypothyroidism is a threat to fertility, pregnancy and fetal development,” Suvi Turunen, MD, of the department of obstetrics and gynecology at Oulu University Hospital in Finland, and colleagues wrote. “Pregnancy increases thyroid hormone requirements, and the need for levothyroxine substitution is known to increase during pregnancy in up to 85% of hypothyroid women. Therefore, women with diminished thyroid reserve are especially at risk for suboptimal treatment.”

Turunen and colleagues conducted a national, register-based cohort study of all singleton births in Finland between 2004 and 2013 (n = 571,785). Data were collected from the Finnish Medical Birth Register.

The researchers also collected data on levothyroxine purchases during pregnancy and in the 3 months before conception, with consistent use defined as having a purchase during each trimester of pregnancy.

During the study period, hypothyroidism was reported in 16,364 pregnancies, making up 3% of the total. In addition, consistent levothyroxine purchasing was met by 37.5% of women with hypothyroidism

Compared with women without hypothyroidism, those with hypothyroidism experienced more gestational diabetes (OR = 1.2; 95% CI, 1.1-1.3), placenta previa (OR = 1.4; 95% CI, 1.2-1.7), elective cesarean section (OR = 1.2; 95% CI, 1.2-1.3) and acute cesarean section (OR = 1.2; 95% CI, 1.1-1.2). Conversely, gestational hypertension (OR = 1.1; 95% CI, 1-1.3) and severe preeclampsia (OR = 0.7; 95% CI, 0.5-1.1) were not significantly associated with hypothyroidism among women who consistently used levothyroxine.

Some perinatal outcomes were also positively affected by levothyroxine use. Women using levothyroxine experienced fewer early (OR = 0.4; 95% CI, 0.3-0.6) and late preterm births (OR = 1; 95% CI, 0.9-1.2) than those without consistent levothyroxine use. However, neonatal ICU admission (OR = 1.2; 95% CI, 1.2-1.3) and large for gestational age newborns (OR = 1.3; 95% CI, 1.2-1.4) were significantly associated with hypothyroidism in the mother regardless of levothyroxine use.

“The odds of gestational hypertension, severe preeclampsia, preterm births and congenital anomalies seemed to be driven by nonconsistent levothyroxine use, as we did not observe these increased odds for mothers with consistent levothyroxine use,” the researchers wrote. – by Phil Neuffer

Disclosures: The authors report no relevant financial disclosures.