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The outcome of pregnancy is normal in women with subclinical hyperthyroidism
The
background of the study. Hyperthyroidism in pregnant women is
associated with an increase in maternal morbidity and fetal morbidity
and mortality. In this study, the frequency of disorders of pregnancy
and of abnormal fetal outcomes was determined in women with subclinical
hyperthyroidism.
How the study was done. Serum thyrotropin (TSH) was measured in 25,765 women who later delivered singleton infants. Serum free thyroxine (T4) was measured in women who had a serum TSH concentration ≤0.2 mU/L. Women with a high serum free T4 concentration were considered to have overt hyperthyroidism, and were evaluated further. Women who had normal serum free T4 concentrations and low serum TSH concentrations were considered to have subclinical hyperthyroidism, and were not further evaluated.
The outcomes of pregnancy in these women were compared with the outcomes in women who had normal serum TSH concentrations. The outcomes included gestational hypertension, preeclampsia, gestational age at delivery, birth weight, major malformations, and perinatal mortality.
The results of the study. Among the 25,765 women, 433 (1.7 percent) had subclinical hyperthyroidism and 23,124 were normal. The average age of the women in both groups was 25 years. Those with subclinical hyperthyroidism had a slightly lower body-mass index (30 vs. 31 kg/m2) and fewer were nulliparous (28 vs. 36 percent).
The frequency of gestational hypertension was lower in the women with subclinical hyperthyroidism (6 vs. 9 percent). There were no differences in the frequency of preeclampsia, diabetes mellitus, placental abruption, gestational age at delivery, or cesarean delivery. There were no differences in gestational age at delivery, birth weight, percentage of infants with low birth weight, or any other fetal outcome.
The conclusions of the study. The course and outcome of pregnancy are normal in women who have subclinical hyperthyroidism during their pregnancy.
The original article. Casey BM, Dashe JS, Wells CE, McIntire DD, Leveno KJ, Cunningham FG. Subclinical hyperthyroidism and pregnancy outcomes. Obstet Gynecol 2006;107:337-41.
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| Thyroid Digest Index | | | July 2006 Thyroid Digest |
