Thyroid Research and Practice

ORIGINAL ARTICLE
Year
: 2013  |  Volume : 10  |  Issue : 2  |  Page : 65--67

Screening for thyroid dysfunction during pregnancy


Jitesh M Shah, Meghana N Mehta, Hiral B Viradia 
 Department of Obstetrics and Gynecology, Surat Municipal Institute of Medical Education and Research (SMIMER), Surat, Gujarat, India

Correspondence Address:
Jitesh M Shah
D-503, Citizen Heights, Opp. Nanavati Motors, Punagam Road, Magob, Surat- 395 010, Gujarat
India

Abstract

Introduction: Thyroid disorders are the second most common endocrine disorders during pregnancy after diabetes mellitus. Materials and Methods: This is a prospective study involving 2000 pregnant women attending antenatal clinic. Women were screened by serum TSH (thyroid stimulating hormone) estimation by chemiluminescent method after informed consent. Estimation of free T3 (FT3) and free T4 (FT4) were advised if the screening test was abnormal. All pregnant women were followed throughout the pregnancy, labor and postpartum period to note any adverse feto-maternal outcome. Results were analyzed by Chi square test. Results: 82.5% of women belong to age group 21-30 years. 45% women were primigravida and 55% were multigravida. Serum TSH level was normal in 94.2% women. 3.5% women had sub clinical hypothyroidism, 0.9% women had overt hypothyroidism and 0.6% had overt hyperthyroidism. Of all women diagnosed of having hypothyroidism 92% had absence of any high risk factor and 85.7% of women diagnosed of having hyperthyroidism had no high risk factor for thyroid disorders. Conclusion: Even though universal screening for thyroid dysfunction is not yet a recommendation, it should be considered.



How to cite this article:
Shah JM, Mehta MN, Viradia HB. Screening for thyroid dysfunction during pregnancy.Thyroid Res Pract 2013;10:65-67


How to cite this URL:
Shah JM, Mehta MN, Viradia HB. Screening for thyroid dysfunction during pregnancy. Thyroid Res Pract [serial online] 2013 [cited 2020 Aug 5 ];10:65-67
Available from: http://www.thetrp.net/text.asp?2013/10/2/65/110585


Full Text

 Introduction



Thyroid disorders are the second most common endocrine disorders during pregnancy after diabetes mellitus. [1],[2],[3] The incidence of sub clinical hypothyroidism is 2 to 3%, of overt hypothyroidism is 0.3 to 0.5% and of hyperthyroidism is 0.1 to 0.4% during pregnancy. [4],[5] Thyroid dysfunction during pregnancy may lead to adverse fetal and maternal outcome. [6],[7],[8]

 Materials and Methods



This is a prospective study involving 2000 pregnant women attending antenatal clinic from April 2009 to December 2011. Approval of institutional ethics committee was obtained prior to conducting the study. Women were screened by serum TSH (thyroid stimulating hormone) estimation by chemiluminescent method after informed consent.

Inclusion criteria: Pregnant woman at her first antenatal visit.

Exclusion criteria: (i) pregnant woman who is a known case of thyroid disease (ii) pregnant woman willing for MTP (iii) refusal of woman to enroll into study (iv) pregnancy with vesicular mole or ectopic pregnancy.

Estimation of free T3 (FT3) and free T4 (FT4) were advised if the screening test was abnormal. Women with overt hypothyroidism and sub clinical hypothyroidism were treated with levothyroxin and women with overt hyperthyroidism were treated with propylthiouracil. Women with sub clinical hyperthyroidism were not treated with any medicine and monitored at regular interval with detailed thyroid function tests. Women with thyroid disorders were monitored by repeat tests every 4 - 6 weeks interval and the doses of the medication were adjusted to keep serum TSH within normal limit. Cord blood TSH estimation was done after delivery to screen for neonatal thyroid disorder in case of women with thyroid disorders.

All pregnant women were followed throughout the pregnancy, labor and postpartum period to note neonatal and maternal outcome. Results were analyzed by Chi square test.

 Results



As shown in [Table 1], 82.5% of women belong to age group 21 to 30 years. Twelve percent women had teenage pregnancy. Forty five percent women were primigravida and 55% were multigravida. Serum TSH level was normal in 94.2% women. Three point five percent women had sub clinical hypothyroidism, 0.9% women had overt hypothyroidism and 0.6% had overt hyperthyroidism [Table 2]. [Table 3] shows that out of all women diagnosed of having hypothyroidism 92% had absence of any high risk factor and 85.7% of women diagnosed of having hyperthyroidism had no high risk factor for thyroid disorders. [Table 4] shows the incidences of various obstetric complications in euthyroid women and in women with thyroid disorders. Complications like spontaneous abortion, hyper emesis gravidarum, pre eclampsia, fetal growth restriction and preterm labor were more in women with thyroid disorders but the differences were not statistically significant (P= 0.068). [Table 5] shows that two new born babies were affected by hypothyroidism born out of 116 pregnant women having thyroid disorder. Mother of one newborn was suffering from overt hypothyroidism and that of other was suffering from overt hyperthyroidism.{Table 1}{Table 2}{Table 3}{Table 4}{Table 5}

 Discussion



Autoimmune thyroiditis remains the most common cause for both hypothyroidism and hyperthyroidism. Grave's disease accounts for more than 85% cases of hyperthyroidism and Hashimoto thyroiditis remains the common cause for hypothyroidism. Endemic iodine deficiency is also a common cause for hypothyroidism during pregnancy. Therefore, iodine status should be normalized in the regions of iodine deficiency. The WHO recommends 200 micrograms of daily iodine intake by the mother. The fetal thyroid gland begins to produce thyroid hormone at about 10 to 12 weeks of gestation, so during first trimester, fetus depends on maternal supply of thyroid hormones which is necessary for fetal growth. From second trimester onwards, the demand is met by the mother and fetus. [1],[2],[4] The availability of thyroxin to the developing fetal neurons is vital for their maturation and proper function. Maternal alteration in thyroid function, overt or sub clinical, can adversely affect the fetus directly by way of transplacental passage of abnormal level of maternal hormone, thyroid antibodies or prescribed medication or indirectly by way of altered maternal gravid physiology. It is desirable to detect any disease in its early stage as early treatment prevents complications. Sub clinical thyroid dysfunction is more prevalent and frequently remains undiagnosed unless a specific screening test is initiated. Screening for thyroid disease is an area often open to argument and criticism. The American association of clinical endocrinology in 2002 has recommended routine screening for thyroid disorders by serum TSH before or during first trimester of pregnancy.

The American College of Obstetrics and Gynecologist in 2002 has recommended that there are insufficient data to warrant routine screening of asymptomatic women (Level C). [9] ACOG recommends thyroid function tests in women having high risk factor for thyroid disorder. High risk factors for thyroid disorders include: (i) H/O of thyroid disorder or therapeutic radiation to head and neck, (ii) signs and symptoms suggestive of thyroid disorder, (iii) family H/O thyroid disorder, (iv) presence of thyroid swelling, (v) presence of thyroid antibodies, (vi) H/O of type I diabetes mellitus, autoimmunity, infertility or miscarriage. In our study, 92% of women with hypothyroidism and 85.7% of women with hyperthyroidism were without any of risk factor for thyroid disorder. The study conducted by Chang et al, Horacek et al, Wang et al and Dosiou et al, showed that about 30-80% cases of hypothyroidism would be missed if only high risk case finding strategy was used for screening. [10],[11],[12],[13] The study conducted by Horacek et al and Wang et al, showed that about 80 to 88% cases of hyperthyroidism would be missed if only high risk case finding strategy was used for screening. Therefore, universal screening for thyroid disorders is recommended. [1],[4],[14],[15]

Various maternal and fetal adverse effects of thyroid disorders in pregnancy are abortion, prematurity, preeclampsia, anemia, Placental abruption, post partum hemorrhage, IUGR, neonatal thyroid dysfunction, neonatal respiratory distress, low IQ of new born etc. [1],[4],[7],[8],[16] In our study incidences of various complications like spontaneous abortion, hyper emesis gravidarum, preeclampsia, IUGR and preterm labor were higher in women with thyroid dysfunction than in euthyroid women but the difference was not significant which may be due to early diagnosis and treatment. The incidences of preterm labor, PIH and LBW were 22%, 17.4% and 12.4% respectively in Nuzhat et al, study. Congenital hypothyroidism occurs in 1 in 2500 to 1 in 4000 babies. Serum T3 and T4 levels rise 30 minutes after delivery and persist for 5 days. This is due to TSH elevation caused by the stress of delivery. So newborn screening should be done from the cord blood or 5 days after delivery. [17]

 Conclusion



Even though universal screening for thyroid dysfunction is not yet a recommendation, it should be considered. Screening by estimation of serum TSH level is sufficient and should be done preconceptionally or early in first trimester.

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