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Isolated hypothyroxinemia tied to adverse maternal, neonatal outcomes
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Isolated hypothyroxinemia during the first trimester of pregnancy is associated with an increased risk for breech presentation, infant macrosomia and cesarean sections, study data show.
Chantal Daumerie , MD, PhD, professor in the division of endocrinology, Cliniques universitaires Saint-Luc in Belgium, and colleagues evaluated 783 women seen for a first-trimester prenatal visit at Cliniques universitaires Saint-Luc between June 2014 and June 2015 to determine the prevalence of first-trimester severe hypothyroxinemia and to evaluate the consequences of the condition on maternal and fetal outcomes.
Overall, 68 participants had first-trimester isolated hypothyroxinemia, 83 had a thyroid-stimulating hormone concentration higher than 2.5 mU/L, 79 had a TSH concentration lower than 0.2 mU/L and 553 were euthyroid.
A selected group of euthyroid controls (n = 165) and a selected group of participants with first-trimester isolated hypothyroxinemia (n = 55) were used to compare maternal and neonatal outcomes. Compared with the control group, the isolated hypothyroxinemia group had an increased BMI at preconception (P = .003), during the first trimester (P = .004) and at the time of delivery (P = .001). However, overall median gestational weight gain was similar between the two groups. More participants in the isolated hypothyroxinemia group underwent cesarean section (32.7%) compared with controls (17.6%; P = .026). More participants in the isolated hypothyroxinemia group showed fetal position in breech presentation (14.3% vs. 3.6% of controls; P = .006). More infants born to mothers in the isolated hypothyroxinemia group had macrosomia compared with infants born to mothers in the control group (P = .026). Gestational diabetes occurred in more participants in the isolated hypothyroxinemia group (14.3%) compared with controls (9.1%).
“The prevalence of [isolated hypothyroxinemia] during the first trimester of pregnancy, defined as [free thyroxine] concentration below the fifth percentile of the institutional range in conjunction with a normal TSH concentration, was 8.7% in our unselected Belgian population,” the researchers wrote. “[Isolated hypothyroxinemia] was associated with an increased maternal BMI and a susceptibility to develop gestational diabetes. Overweight could be a potential risk factor for thyroid dysfunction in pregnant women and, specifically, hypothyroxinemia. There was also evidence that hypothyroxinemia in early pregnancy is related to an increased risk of breech presentation at birth, a significant increase in macrosomia and in cesarean sections.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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