Treatment of Subclinical Hypothyroidism Not Warranted During Pregnancy

Pregnant woman at the doctor's office.
Pregnant woman at the doctor’s office.
Current trial evidence does not support the treatment of subclinical hypothyroidism diagnosed in pregnancy.

Treatment of subclinical hypothyroidism in pregnancy failed to confer any benefit on important obstetric and neonatal outcomes and had no effect on childhood IQ and neurobehavioral outcomes, according to a study published in BMJ Open.

It remains unclear whether subclinical hypothyroidism in pregnancy — a condition that occurs in more than 25% of pregnant women — is associated with adverse obstetric outcomes, as observational studies to date have reported inconsistent associations. In this study, the researchers conducted a systematic review and meta-analysis to assess the impact of subclinical hypothyroidism diagnosed in pregnancy and to determine whether levothyroxine treatment would be beneficial to obstetric or childhood outcomes compared with control treatment. A total of 3 randomized controlled trials with a combined cohort of 1837 participants were included. Data from an unpublished study supplemented the meta-analysis.

Two studies included in the meta-analysis assessed maternal and neonatal outcomes and 2 studies investigated childhood IQ. No significant differences were observed between those receiving levothyroxine vs control groups for any obstetric outcomes. A single trial not included in the meta-analysis indicated that rates of stillbirth or miscarriage were similar in both groups (1% vs 2% for levothyroxine and placebo, respectively; P =.36). Additionally, rates of gestational diabetes (7% both arms; P =.66), gestational hypertension (10% vs 11%; P =.69), preeclampsia (6% both groups; P =.76), and neonatal death (0 vs <1%; P =.5) were similar between levothyroxine and placebo groups. For childhood IQ, the meta-analysis showed no significant difference between levothyroxine vs control (mean difference −0.69; 95% CI, −2.15 to 0.78; P =0.36).

“Current trial evidence does not support the treatment of subclinical hypothyroidism diagnosed in pregnancy,” concluded the researchers.

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Yamamoto JM, Benham JL, Nerenberg KA, Donovan LE. Impact of levothyroxine therapy on obstetric, neonatal and childhood outcomes in women with subclinical hypothyroidism diagnosed in pregnancy: a systematic review and meta-analysis of randomised controlled trials. BMJ Open. 2018;8:e022837