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A prospective study of hypothyroidism during pregnant attending tertiary care hospital in south India

Normal functioning of thyroid gland is essential during pregnancy for both mother and growing foetus. For normal growth and development of foetus adequate transplacental transfer of thyroid hormone is essential as synthesis and secretion of thyroid hormone in foetus start only after 20 week of gestation. Disorder of thyroid function is common during pregnancy and hypothyroidism is more common then hyperthyroidism affecting 3–5% of all pregnant women. There are various factor which is responsible for abnormal thyroid function like during pregnancy there occurs increase in thyroid hormone binding globulin (TBG) level which increase the need for T3 and T4 production throughout pregnancy. There is increased degradation of thyroid hormone by placental, chorion, and amnion type 3 inner ring deiodinase. Serum thyroid antibody positivity is also common during pregnancy.


INTRODUCTION
Normal functioning of thyroid gland is essential during pregnancy for both mother and growing foetus. For normal growth and development of foetus adequate transplacental transfer of thyroid hormone is essential as synthesis and secretion of thyroid hormone in foetus start only after 20 week of gestation. 1,2 Disorder of thyroid function is common during pregnancy and hypothyroidism is more common then hyperthyroidism affecting 3-5% of all pregnant women. 3,4 There are various factor which is responsible for abnormal thyroid function like during pregnancy there occurs increase in thyroid hormone binding globulin (TBG) level which increase the need for T3 and T4 production throughout pregnancy. There is increased degradation of thyroid hormone by placental, chorion, and amnion type 3 inner ring deiodinase. Serum thyroid antibody positivity is also common during pregnancy. [5][6][7] There is a well established association between maternal hypothyroidism and adverse outcome of pregnancy. 8,9 Maternal hypothyroidism is associated with both maternal adverse effects like preeclampsia, ecclampsia, pregnancy induced hypertension and gestational diabetes mellitus and foetus complication like low birth weight, pre term birth, neurological deformities and abnormal presentation. 10,11 Dhanwal DK, Bajaj S, Rajput R, et al in their prevalence study from 11 cities in 9 states of India has concluded that there is a high prevalence of hypothyroidism (13.13%), in pregnant women during the first trimester from India and universal screening of hypothyroidism may be desirable in our country. 12 Kalra B, Choudhary M, Thakral M, Kalra S et al has concluded that Hypothyroidism is common in term pregnancies. If treated adequately, healthy fetomaternal outcomes can be achieved. 13 Present study has been undertaken to know the prevalence of hypothyroidism in our region and its presentation and also to follow the patients till delivery after adequate treatment.

Place of study
Present study has been conducted in the department of obstetrics and gynaecology Konaseema institute of medical science Amalapuram Andhra Pradesh India.

Duration of study
It has been conducted from January 2018 to August 2020.

Type of study
This is a prospective observational study.

Selection of patients
All pregnant women attending antenatal outpatient department for their first antenatal check-up were approached and in addition to routine lab investigation thyroid function test was advised. Out of them patients were selected based o following inclusion and exclusion criteria.

Inclusion criteria
1) All singleton pregnancy in first and second trimester 2) Overt and subclinical patients with or without treatment

Sample size
Based on above criteria 120 patients were enrolled for this study.

Method
In present study 120 patients with overt and subclinical hypothyroidism were included in this study. Detailed histories of patients were taken and clinical examination was done and data was collected in a predesigned Performa. We used standard diagnostic criteria for diagnosis of overt and subclinical hypothyroidism 15, 16. For estimation of thyroid hormone we used radioimmunoassay and Solid Phase Two-Site ImmunoRadoMetric Assay technique. All women enrolled for this study were followed for till delivery to see that they develop any complication and know the outcome of pregnancy. All patients were treated as per standard treatment protocol.

Statistical analysis
Data were recorded in excel sheet and statistical Analysis was done with software SPSS-14 version. Data were calculated as percentage and proportions.

RESULTS
In present study during study period 980 patients attending obstetrics outpatient department were evaluated for hypothyroidism out of them 120 patients with hypothyroidism were enrolled for this study.

DISCUSSION
We have evaluated 980 women with pregnancy for hypothyroidism during our study period of two years and eight months and observed that 12.22% women have hypothyroidism. Dhanwal DK, Bajaj S, Rajput R, et al has reported from his multicentric study that prevalace of hypothyroidism during pregnancy in India to be 13.13% and in Andhra Pradesh to 8.94% which is little less than our study but close to whole India prevalence. 12 Korde VR, Barse SP, Barla JS et al has reported that in his study the prevalence was 14% which is similar to our study. 16 We have observed that hypothyroidism during pregnancy is more common in primi. Most common age was from 31 to 40 years and was commonly detected before 10 weeks of gestation which is supported by the work of Vimal Nambiar, Varsha S. Jagtap, Vijaya Sarathi et al. 17 In present study most of the patient TSH was between 5 to 10 mIU/ml and at the time of admission 60% patient were taking treatment and 40 % patient were not treated. Which is supported by the work of Vimal Nambiar et al and Teng X, Shan Z, Chen Y, Lai Y, Yu J, Shan L, et al. 17,18 In our study pregnancy induced hypertension, oligohydramnios and preterm delivery was more common than abortion in second trimester and missed abortion. This finding corroborates with the study of Tudosa R, Vartej P, Horhoianu I, Ghica C, Mateescu S, Dumitrache Iet al and Casey BM, Dashe JS, Wells CE, et al. 19,20 Regarding mode of delivery in our study normal vaginal delivery was most common (48.33%). Tudosa R, Vartej P, Horhoianu I, Ghica C, Mateescu S, Dumitrache I et al has reported that spontaneous delivery was 53.33% which is little higher the our study. Elective CS was mode of delivery in 28.33% and emergency CS was mode of delivery in 16.66% which is less than the study of Tudosa R, Vartej P et al. 19 Casey BM, Dashe JS, Wells CE, et al has concluded that Preterm birth, defined as delivery at or before 34 weeks of gestation, was almost 2-fold higher in women with subclinical hypothyroidism which support our study. 20

CONCLUSION
From our study we can conclude that the prevalence of hypothyroidism in our region was 12.22%. Hypothyroidism during pregnancy is more common in primi. Most common age group was third decade and was commonly detected before 10 weeks of gestation. Pregnancy induced hypertension, oligohydramnios and preterm delivery was more common than abortion in second trimester and missed abortion. Normal vaginal delivery was common then elective or emergency CS.