Prevalence of hypothyroidism in pregnancy

 

Vyakaranam Hema^1*, Sirineni Yamuna², Kasam Ujwala⁴, Kushanapalli Anusha⁵

 

Abstract              Background: Maternal hypothyroidism may place the mother at an increased risk of adverse obstetrical outcomes. Untreated hypothyroidism is associated with increased risk for preeclampsia, low birth weight, placental abruption, miscarriage, and perinatal mortality. Maternal hypothyroidism is a common clinical problem and its early detection is very important. Aim of the study: To study prevalence of hypothyroidism in pregnancy at Cure well Hospital, Srinivas Colony, Warangal, Telangana. Material and Methods: This was a prospective cross sectional study done on 76 pregnant women at department of obstetrics and gynecology at Cure Well Hospital, Srinivas Colony, Warangal, Telangana for duration of six months. Results: The prevalence of hypothyroidism was 11% in our study. 51.3% cases were among 18-24 years followed by 42.1% among 26-30 years and 60.5% had subclinical hypothyroidism, 39.4% had overt hypothyroidism. Primigravidae were more commonly affected by hypothyroidism in pregnancy. Conclusion: The over all prevalence of hypothyroidism in pregnancy is quite high and maternal hypothyroidism is mostly seen in primigravida cases. Early detection, prompt initiation of treatment and adequate follow-up of hypothyroidism in pregnancy is very important for the fetal and maternal well being.

Key Words: Hypothyroidism, Serum TSH, Primigravida, Subclinical hypothyroidism

 

INTRODUCTION

Pregnancy is a physiological state of complex metabolic stress that involves significant changes in hormonal milieu. It has a profound influence on thyroid gland structure as well as function. Hypothyroidism during pregnancy constitutes a significant health challenge, as it is associated with adverse maternal outcome along with an impact on neonatal cognitive development. The foetal thyroid gland starts to function only after 12-14 weeks of gestation. As a consequence, the growing foetus remains dependent upon maternal thyroid hormones during this phase of early gestation.^1,2 Thyroid hormones (thyroxine and triiodothyronine) are vital for normal foetal neurological development^3,4 and decreased levels predispose the child to develop cognitive delay in early adolescence.⁵ The prevalence of hypothyroidism during pregnancy is variable, and this variability is mostly attributed to differences in geographical areas, analytical measurement and trimester-specific TSH limits used in diagnosis.⁶ In general, the prevalence rates were estimated to be 0.25%-2.5% for subclinical hypothyroidism (SCH), 0.2%-0.3% for overt hypothyroidism (OH)⁷ and 5%-15% for euthyroidism with autoimmune disease.⁸ Classification of hypothyroidism recognized during pregnancy is essential for epidemiological as well as clinical reasons. The American Thyroid Association (ATA) has defined hypothyroidism during pregnancy as the state of increased TSH level when other rare causes, such as TSH-secreting pituitary tumor and thyroid hormone resistance are excluded. Primary maternal hypothyroidism (MH) observed during pregnancy should be distinguished from preexisting hypothyroidism diagnosed prior to the pregnancy. Two main varieties of primary MH are recognized by the ATA: overt hypothyroidism (OH) and subclinical hypothyroidism (SCH) based on the presence of elevated TSH and whether FT₄ level is decreased or within normal range. However, cases of isolated hypothyroxinaemia (IH) with normal TSH have also been recognized by the ATA as a third sub-type of MH.⁹ Women with hypothyroidism have decreased fertility; even if they conceive, risk of abortion is increased, and risk of gestational hypertension, anemia, abruptio placenta and postpartum hemorrhage are increased.¹⁰ A number of pioneering studies by Man et al.,¹¹ Haddow et al.,¹² and newer studies by Rovet et al.¹³ and Pop et al.,¹⁴ have conclusively proven that children born to mothers with hypothyroidism have a significantly increased risk of impairment in intelligence quotient (IQ) scores, neuropsychological developmental indices and learning abilities.

 

AIM OF THE STUDY

To study the prevalence of hypothyroidism in pregnancy at Cure Well Hospital, Srinivas Colony, Warangal, Telangana.

 

MATERIALS AND METHODS

This was a prospective cross-sectional study done over a period of six months from August 2019 to February 2020.

All consecutive pregnant women who gave written consent were included in the study.

The present study included pregnant women aged 18-35 years and presenting at first trimester of pregnancy attending the antenatal clinic in Obstetrics department of Cure Well Hospital, Warangal Telangana.

No ethical issues were involved in the study.

 

METHODOLOGY

Pregnant women included in the study were selected randomly.

A questionnaire was prepared and detailed history was taken from all the pregnant women including age of the woman, gestational age, parity, menstrual history, obstetrics history, history of past illness if any, history of any drug intake and others. A total of 664 pregnant women attended antenatal clinical at our hospital during the study period of which 76 pregnant women had elevated TSH and these 76 women were considered for the present study. They were dived into 2 groups based on FT3 and FT4 status into Subclinical hypothyroids (SCH) and overt hypothyroids (OHT). General examination was done and the blood samples from all the cases were sent for investigations such as routine investigations of complete blood picture (CBP) and coplete urine analysis (CUE), blood group and Rh typing. Biochemical investigations included thyroid function test and fasting blood sugar, total cholesterol, triglycerides, serum creatinine, and blood urea nitrogen. Estimation of thyroid stimulating hormone (TSH), free T4, and anti‑TPO antibodies was carried out using Chemiluminescence immunoassay (CLIA) technology.

Inclusion criteria:

Pregnant women who are willing to participate in the study

Age 18 years to 35 years

Pregnant women with clinical history of hypothyroidism

Pregnant women with raised TSH and normal T3 or T4

Pregnant women with raised TSH and low T3 or T4

Exclusion criteria:

Patients who are unwilling to participate in the study

Age less than 18 years and more than 35 years

Pregnant women with raised T3 or T4 levels

Pregnant women with other medical history

Data was entered into excel sheets and the percentages and ratios were calculated.

 

RESULTS

A total 76 cases were included in the study. The age ranged from 18 to 35 years and the mean age of the study population was 23.5 years. Serum TSH value was tested in 1st trimester between 6-10 weeks period of gestation for all pregnant women. The estimation of free T4 levels was done to reclassify those with thyroid dysfunction as subclinical or overt hypothyroidism.

 

Table 1: Age distribution

In the present study age ranged from 18 to 35 years. Majority were among the 18-24 years age group. Least number of hypothyroid pregnant women were in the 31-35 years age group.

 

Table 2: Distribution according to parity

In the present study, majority were primigravida, 63.1% (48/76) and 36.8%(28/76) were multigravida.

 

Table 3: Distribution according to thyroid function status

Subclinical hypothyroidism cases were more common than overt hypothyroidism.

PREVALENCE:

The prevalence of hypothyroidism was 11 %

Prevalence: Total number of cases with hypothyroidism x 100/

Total number of pregnant cases = 76 x100

---------

 664

 = 11%

Prevalence of subclinical ypothyroidism was 6.05%.

Prevalence of overt hypothyroidism was 3.94%.

 

DISCUSSION

Comparative studies related to age distribution: In the present study, majority of the cases were among 18-24 years, ie. 51.3% (39/76), followed by 26-30 years ie, 42.1% (32/76). The mean age of the study population was 23.5 years. In the study by Kiran et al.¹⁵ they observed majority of cases in advanced age group ie, in the 26-33 years age group ie, 403 (56.9%) cases, and next common age group was 34 to 40 years with 200 (28.2%) cases. In the study by Dhanwal DK et al. study¹⁶ the mean age of the study population was 25.5 ± 5.6 years whereas in our study, the mean age of study population was 23.5 years.

Comparative studies related to gestational age: In the present study, majority of the women 63.1% (48/76) were primigravida, and 36.8% (28/76) were multigravida. Similar findings were observed in a study by Chandrasekhara P et al.¹⁷ where 175 (42.78%) patients were primigravida and 234 (57.22%) patients were multigravida. Kiran et al.¹⁵ in their study reported 221 (32.2%) as primiparous and 110 (16.0%) as multiparous. Our findings compare well with the above studies.

Comparative studies related to hypothyroidism: In our study, we observed 60.5% (46/76) cases having subclinical hypothyroidism, 39.4% (30/76) cases having overt hypothyroidism and 08 cases (10%) of hypothyroid pregnant women who were positive for anti‑TPO antibodies of which 05 had subclinical hypothyroidism and 03 had overt hypothyroidism. In the study done by Chandrasekhara P et al.¹⁷ they observed 20 cases (83.33%) as subclinical hypothyroidism and 04 (16.77%) cases as overt hypothyroidism and 06 (25%) cases had raised anti TPO levels of which 03 had subclinical hypothyroidism and 03 had overt hypothyroidism. Whereas, Dhanwal DK et al.¹⁶ reported 13.1% of pregnant women to be hypothyroid (n = 388) and 40% (n = 155) of hypothyroid pregnant women were positive for anti‑TPO antibodies. Kiran et al.¹⁵ observed that hypothyroidism diagnosed during pregnancy Uncategorized was 14 (2.0%), Overt hypothyroidism was 13 (1.8%) and Subclinical hypothyroidism was 43 (6.1%).

Comparative studies related to prevalence: In the present study, the prevalence of hypothyroidism was 11%. In the study done by Pillai NS et al.¹⁸ the prevalence of thyroid dysfunction was 10.8%, whereas, Agrawal U et al.¹⁹ observed the prevalence of hypothyroidism in pregnancy around 2.5% and Dhanwal DK et al.¹⁶ reported the prevalence of hypothyroidism as 15.1% in first trimester. In the study by Goel P et al.²⁰ the overall prevalence of hypothyroidism was 6.3% (overt 2.9% and subclinical 3.4%) in pregnancy. The prevalence of hypothyroidism was comparable to the other studies.

 

CONCLUSION

The overall prevalence of hypothyroidism in pregnancy is quite high and maternal hypothyroidism is mostly seen in primigravida cases. Early detection, prompt initiation of treatment and adequate follow-up of hypothyroidism in pregnancy is very important for the fetal and maternal well being.

 

REFERENCES

1. de Escobar GM, Obregón MJ, del Rey FE. Maternal thyroid hormones early in pregnancy and fetal brain development. Best Pract Res Clin Endocrinol Metab. 2004;18:225-248.
2. de Escobar GM, Obregón MJ, del Rey FE. Iodine deficiency and brain development in the first half of pregnancy. Public Health Nutr. 2007;10:1554-1570. 
3. Matsuura N, Konishi J. Transient hypothyroidism in infants born to mothers with chronic thyroiditis- a nationwide study of twenty-three cases. The Transient Hypothyroidism Study Group. Endocrinol Jpn. 1990;37:369-379.
4. Williams GR. Neurodevelopmental and neurophysiological actions of thyroid hormone. J Neuroendocrinol. 2008;20:784-794.
5. Henrichs J, Bongers-Schokking JJ, Schenk JJ, Ghassabian A, Schmidt HG, Visser TJ, et al.. Maternal thyroid function during early pregnancy and cognitive functioning in early childhood: the generation R study. J Clin Endocrinol Metab. 2010;95:4227-4234. 
6. Amouzegar A, Mehran L, Sarvghadi F, Delshad H, Azizi F, Lazarus JH. Comparison of the American Thyroid Association with the Endocrine Society practice guidelines for the screening and treatment of hypothyroidism during pregnancy. Hormones (Athens). 2014;13:307-313.
7. Thung SF, Funai EF, Grobman WA. The cost-effectiveness of universal screening in pregnancy for subclinical hypothyroidism. Am J Obstet Gynecol. 2009;200:267.e1-267.e7.
8. Glinoer D, Abalovich M. Unresolved questions in managing hypothyroidism during pregnancy. BMJ. 2007;335:300-302.
9. Stagnaro-Green A, Abalovich M, Alexander E, Azizi F, Mestman J, Negro R, et al.. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid. 2011;21:1081-1125.
10. Abalovich M, Gutierrez S, Alcaraz G, Maccallini G, Garcia A, Levalle O. Overt and subclinical hypothyroidism complicating pregnancy. Thyroid 2002;12:63-6.
11. Man EB, Jones WS, Holden RH, Mellits ED. Thyroid function in human pregnancy, Retardation of progeny aged 7 years: Relationships to maternal age and maternal thyroid function. Am J Obstet Gynecol 1971;111:905-16.
12. Haddow JE, Palomaki GE, Allan WC, Williams JR, Knight GJ, Gagnon J, et al.. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999;341:549-55.
13. Rovet JF. Neurodevelopmental consequences of maternal hypothyroidism during pregnancy (abstract 88;annual Meeting of the American Thyroid Association). Thyroid 2004;14:710
14. Pop VJ, Kuijpens JL, van Baar AL, Verkerk G, van Son MM, de Vijlder JJ, et al.. Low maternal free thyroxine concentrations during early pregnancy are associated with impaired psychomotor development in infancy. Clin Endocrinol (Oxf) 1999;50:149-55.
15. Kiran Z, Sheikh A, Malik S, Meraj A, Masood M, Ismail S, et al.. Maternal characteristics and outcomes affected by hypothyroidism during pregnancy (maternal hypothyroidism on pregnancy outcomes, MHPO-1)BMC Pregnancy and Childbirth (2019) 19:476.
16. Dhanwal DK, Bajaj S, Rajput R, Subramaniam KAV, Chowdhury S, Bhandari R, et al.. Prevalence of hypothyroidism in pregnancy: An epidemiological study from 11 cities in 9 states of India. Indian Journal of Endocrinology and Metabolism 2016;20;387-390.
17. Chandrasekhara P, Aslam M, Kala K, Sultana F. A Study of Thyroid Disorder During Pregnancy. Assam Journal of Internal Medicine 2015;5(2):21-25.
18. Pillai NS, Bennett J. Prevalence of hypothyroidism amongst pregnant women: a study done in rural set up. Int J Reprod Contracept Obstet Gynecol. 2018;7(4):1586-1591.
19. Agrawal U, Shrivastava P, Shrivastava S. Hypothyroidism and anemia in pregnancy Int J Adv Med. 2016;3(4):851-854.
20. Goel P. Kaur J. Saha PK, Tandon R, Devi L. Prevalence, Associated Risk Factors and Effects of Hypothyroidism in Pregnancy: A Study from North India Gynecol Obstet Invest 2012;74:89–94.