Overt and Subclinical Hypothyroidism Complicating Pregnancy

Abstract

We studied the evolution of 150 pregnancies corresponding to 114 women (16-39 years old) with primary hypothyroidism. Fifty-one pregnancies (34%) were conceived under hypothyroidism: 16 overt (X +/- standard deviation [SD], thyroxine [T4]: 2.44 +/- 0.7 microg/dL; thyrotropin [TSH]: 33.4 +/- 8.82 mIU/L), and 35 subclinical hypothyroidism (T4: 6.93 +/- 1.88 microg/dL; TSH: 12.87 +/- 8.43 mIU/L); 99 pregnancies were conceived under euthyroidism while undergoing thyroid therapy. When treatment with levothyroxine was inadequate, the outcome of pregnancy was abortion in 60% of overtly hypothyroid patients and in 71.4% of subclinically hypothyroid patients, premature delivery in 20% and 7.2% respectively, and term delivery in 20% and 21.4%, respectively. When treatment was adequate, 100% of overtly hypothyroid patients and 90.5% of subclinically hypothyroid patients carried pregnancies to term; there were no abortions in any of the groups. Abortions, premature and term deliveries in patients who were euthyroid on levothyroxine at the time of conception were 4%, 11.1% and 84.9% respectively. Of the patients receiving levothyroxine therapy before conception, 69.5% had to increase the dose (mean increase 46.2 +/- 29.6 microg/d). Of 126 evaluated newborns, 110 were delivered at term while 16 were premature. Eight newborns, 4 were premature, had congenital malformations (6.3%), and 4 died. Our results show that the evolution of pregnancies did not depend on whether the hypothyroidism was overt or subclinical but mainly on the treatment received. The adequate treatment of hypothyroidism during gestation minimizes risks and generally, makes it possible for pregnancies to be carried to term without complications.

Thyroid stimulating hormone levels rise after assisted reproductive technology

“…Hypothyroidism, both overt and subclinical, affects 3-5 % of reproductive-aged women [6,16]. The effects of overt hypothyroidism on fertility include impaired ovulation [13], lower clinical pregnancy rates after assisted reproductive technology (ART) [17], higher miscarriage rates [5] and poor obstetrical outcomes [1,4]. In early pregnancy, high human chorionic gonadotropin (HCG) levels stimulate thyroid function through their receptor homology.…”

To study the neonatal outcomes in pregnancies with hypothyroidism in a tertiary referral centre

“…12 Maternal thyroid hypofunctions and pregnancy outcomes has also been studied in Western Countries by many authors including Glinoer et al Green S et al Negro et al and Abalovich et al [14][15][16] Their studies have established a strong association between the hypothyroidism and adverse pregnancy outcomes.…”

11 Hypothyroidism in Pregnancy

“…In areas of iodine sufficiency, the most common cause of hypothyroidism in pregnant women is chronic autoimmune thyroiditis [49]. Anti-thyroid antibodies were found in 18% of Australian women in the late first trimester and were associated with subtle effects on thyroid function [50].…”

“…Women with hypothyroidism have decreased fertility; even if they conceive, risk of abortion is increased, and risk of gestational hypertension, anemia, abruption placenta and postpartum hemorrhage is increased [49] The association between overt maternal hypothyroidism, particularly in early pregnancy, and adverse obstetric outcomes is well-established. In a study of women during the second trimester of pregnancy, the prevalence of fetal death was over 4-fold higher in mothers with a TSH concentration ≥6 mIU/L, compared to those whose mothers had a TSH <6 mIU/L (3.8% vs. 0.9%) [37] Untreated hypothyroidism is associated with increased risk of preeclampsia, low birth weight, placental abruption, miscarriage, and perinatal mortality [53,54].…”

“…The risk of pregnancy complications is greater in women with overt, rather than subclinical hypothyroidism [49].…”