"Pregnancy outcomes in 24,883 women were analyzed for pregnancy hypertension, classified as gestational hypertension, mild preeclampsia, or severe preeclampsia. The incidence of hypertensive disorders were compared between the three cohorts. The overall incidences of hypertension in pregnancy were 6.2%, 8.5%, and 10.9% in the subclinical hyperthyroid, euthyroid, and subclinical hypothyroid groups, respectively, and were found to be significant when unadjusted (P=.016). After adjusting for confounding factors, there was a significant association between subclinical hypothyroidism and severe preeclampsia (adjusted odds ratio 1.6, 95% confidence interval 1.1–2.4; P=.03).
CONCLUSION: Women with subclinical hypothyroidism identified during pregnancy have an increased risk for severe preeclampsia when compared with euthyroid women."
"For the purposes of the current study, normal values were considered to be those that comprised the range from the 2.5th to 97.5th percentiles for the entire cohort. For TSH, these values were 0.03 to 4.13 milliunits/L and for free T4 these values ranged from 0.9 to 2.0 ng/dL. All women screened and delivered at Parkland Hospital and without evidence of overt thyroid dysfunction were included... Women with serum TSH values within the normal range were considered to be euthyroid. Those with an abnormally low TSH but normal free T4 levels were classified as having subclinical hyperthyroidism. Conversely, women with abnormally high TSH but normal free T4 levels were classified as having subclinical hypothyroidism."
"The one salient finding of this study that included nearly 25,000 pregnant women was that those identified to have subclinical hypothyroidism had a significantly increased risk for development of severe preeclampsia when compared with euthyroid women. This association is particularly strong because its significance persisted after adjustment for factors known to increase preeclampsia risks, such as age, parity, race, and weight."
Something else I learned from this study: ".... individuals with subclinical hypothyroidism have impaired endothelium-derived vasodilatation from diminished nitric oxide secretion that is restored after thyroxine (T4) replacement."
http://journals.lww.com/greenjournal/Fu ... of.17.aspx