Prevalence of hypothyroidism in pregnancy and its feto-maternal outcome

Background: Thyroid disorders are among the most common endocrine disorders in pregnant females. Hypothyroidism is more common during pregnancy than hyperthyroidism. The overall prevalence of subclinical hypothyroidism in general population has been reported to be 4% -8.5% while overt hypothyroidism is 0.2 – 0.3% (2). Objective: To evaluate the prevalence of hypothyroidism in pregnancy and to determine association of feto-maternal outcome with hypothyroidism. Material and Methods: A Prospective study conducted over 120 patients who came to routine antenatal care and/or admitted in labour room of Subharti Hospital, Dehradun over a period of 01 year. Women with singleton pregnancy irrespective of the period of gestation were randomly selected for the study. Patients thus selected were divided into two groups: Control Group: This comprised of pregnant females in whom serum TSH and FT4 levels were found to be within normal range on estimation. Study Group: This group included pregnant females who were diagnosed as cases of subclinical hypothyroidism on the basis of raised TSH and normal TF4 levels and overt hypothyroidism on basis of raised TSH and decreased TF4. Results: The prevalence of hypothyroidism came out to be 24.29%. Higher rate of still births, hyperbilirubinemia and admission to neonatal ICU (foetal distress, meconium stained liquor) in the hypothyroid group were observed. Conclusion: Hypothyroidismcontinues to be an important medical condition in pregnancy with significant feto-maternal morbidity. Due to the adverse effect of maternal thyroid disorder on maternal and fetal outcome, timely diagnosis and initiation of treatment of hypothyroid disorders is essential.


Introduction
Thyroid disorders are among the most common endocrine disorders in pregnant females. Hypothyroidism is more common during pregnancy than hyperthyroidism [1]. Pregnancy is associated with significant but reversible changes in maternal thyroid physiology that can lead to confusion on the diagnosis or evaluation of thyroid abnormalities. Subclinical hypothyroidism is defined as increase in serum TSH usually (4-10Mu/L) associated with normal concentration of serum thyroxine and triiodothyronine.
Overt hypothyroidism is diagnosed when high serum thyrotropin level is accompanied by abnormal low thyroxine level. The overall prevalence of subclinical hypothyroidism in general population has been reported Manuscript received: 20 th December 2018 Reviewed: 30 th December 2018 Author Corrected: 6 th January 2019 Accepted for Publication: 10 th January 2019 to be 4% -8.5% while overt hypothyroidism is 0.2 -0.3% [2] Women with hypothyroidism can still conceive, although infertility rates are higher and failure of in vitro fertilization is more likely. Pregnant women with hypothyroidism have a greater risk of early and late obstetric complications such as miscarriage, anaemia, gestational hypertension, placental abruption, premature delivery, post-partum haemorrhage and admission of their baby to neonatal intensive care (particularly for RDS) [3].
The detrimental effects of maternal thyroid deficiency on foetal development are thought to depend on the severity and early onset of a reduced availability of maternal thyroid hormones. Recent studies indicate that undiagnosed (and hence untreated) hypothyroidism during the first half of pregnancy is associated with a risk of poorer neurodevelopment outcome in the progeny [4].

Material and Methods
Thestudy was conducted over 120 patients who came to routine antenatal care or were admitted in labour room of Subharti Hospital, Dehradun over a period of one year (from 1st May 2015 to 30th April 2016).

Inclusion criteria
Among the pregnant women who attended antenatal clinic or were admitted in labour room, women with singleton pregnancy irrespective of the period of gestation were randomly selected for the study. Patients were divided into two groups:

Control Group:
This comprised of pregnant females in whom serum TSH and FT4 levels were found to be within normal range on estimation.

Study Group:
This group included pregnant females who were diagnosed as cases of subclinical hypo-thyroidism on the basis of raised TSH and normal TF4 levels and overt hypothyroidism on basis of raised TSH and decreased TF4. 10 cases were diagnosed as hypothyroid but had pregnancy loss were dropped out from the study as they could not be followed for maternal and fetal outcome

Original Research Article
Obsgyne Review: Journal of Obstetrics and Gynecology Available online at: www.medresearch.in 9 |P a g e  Table 2 shows the relationship of screening for detection of hypothyroidism with high risk factor. Out of 100 patient underwent screening, 13 patients from control group and 7 patients from study group showed risk factor such as, bad obstetrics history such as still birth or recurrent abortions. Diabetes was present in 1 patient from control group and in 2 patients from study group.
On statistical analysis the correlation was found to be significant (p<0.05) patients with history of Type-I DM and BOH.  Foetal distress, MSAF was observed in 25 patients of control group and in 9 patients of study group. On statistical analysis the result was found to be significant P < 0.05.

Original Research Article
Obsgyne Review: Journal of Obstetrics and Gynecology Available online at: www.medresearch.in 10 |P a g e On statistical analysis the incidence of still births and ICU admission rates & hyperbilirubinemia were found to be significant between two groups.

Discussion
Considering the widespread clinical implications of gestational hypothyroidism and its sequelae, the present study was aimed to study the prevalence of hypothyroidism in pregnancy and its feto-maternal outcomes. The study was carried out on 107 patients, who presented to antenatal care in Subharti Hospital Dehradun over a period of one year from 1 st May 2015 to 30 th April 2016.
The women were followed up till delivery. The study population consisted of 81 normal patients and 19 hypothyroid patients diagnosed and followed up. 7 hypothyroid patients were dropped out from study. In our study, the prevalence of hypothyroidism came out to be 24.29% while in a study by Saki F et al. found the prevalence of hypothyroidism 13.7% out of which 2.4% was clinical and 11.3% was sub-clinical [5].
Another study by Sahu HT et al. noted that the prevalence of thyroid dysfunction was high, with subclinical hypothyroidism in 6.47% and overt hypothyroidism in 4.58% women [6]. The variation in prevalence of hypothyroidism may be due to difference in defined normal range of TSH.
Considering the distribution of cases in study population, in the study group, 19 women were included, these were the women who were diagnosed as hypothyroid on the basis of serum TSH and Free T4 levels. In control group, 81 women who had normal thyroid function test on screening. They included the remaining 81 patients of study population.  [6,7,8].

Relationship of Screening for hypothyroidism with individual high risk factors
Positive correlation was found between risk factors as bad obstetric history and Type -I diabetes. 35% with BOH developed hypothyroidism which was statistically significant with P<0.05.16 patients, out of 19 hypothyroid patients in the study group had one or the other risk factor, whereas 3 patients (15.78%) were without any risk factors.De vivo et al also found that the occurrence and timing of pregnancy loss is related to hypothyroidism [9]. Bijay Viadyaet al. showed that the prevalence of raised TSH was higher in the high risk group [10].

Study by Brain M. Casey, Jodi S. Dash et al in 2005
showed that pregnancy in women with subclinical hypothyroidism was three times more likely to be complicated by placental abruption when compared with healthy pregnant women [11]. Similar results were shown by Goel P, et al in their study on 30 patients with subclinical hypothyroidism in 2005. They found an incidence of 0.3% placental abruption in their study group which was not significant [12].

Comparison of mode of delivery in the control and study groups
In the present study, we found that 8 out of 19 (42.11%) in the study groupcompared to 16 of 81 (19.76%) patients in the control group were delivered by caesarean section as on statistical analysis the difference was significant (p<0.05).
Comparable results were shown in a study by Sahu

Original Research Article
Obsgyne Review: Journal of Obstetrics and Gynecology Available online at: www.medresearch.in 11 |P a g e

Comparison of preterm birth in control and study group
The present study showed preterm birth defined as delivery before 34 weeks 42.11% in the study group compared to 9.87% of controls, which was found to be statistically significant with p<0.05 (p value 0.003). Study by Brain M. Casey, Jodi S et al in 2005 Aziz Nuzhat, Reddi Pranathi et al in 2006 also showed increased incidence of preterm delivery in hypothyroid group [7,14].

Comparison of cases according to birth weights
The present study showed significant proportion of babies having low birth weight 31.6% of infants weighed <2.0kg in the study group as compared to 6.17% of the control group (p value 0.002). Similar results were observed in studies conducted by Aziz Nuzhat et al., Idris I., Srinivasan et al [7,13]. Another similar study by Goel P et al. showed 13.3% incidence of low birth weight with 20% evidence of foetal distress [12].

Comparison of cases according to fetal distress
The present study showed 47.36% of study group having foetal distress in labour, 3 babies out of 19 had still birth that is 15.8% and 1 out of 19 had congenital anomalies i.e.5.3%. The foetal distress was found to be significant (p<0.05) in relation to the control group and were comparable to the studies by Brain M Casey et al.which showed that admission to the neonatal intensive care nursery and respiratory distress were twice as likely in infants delivered of women with sub clinical hypothyroidism [14]. Another similar study by Goel P et al. observed 13.3% incidence of low birth weight and 20% had evidence of foetal distress [12].
Considering the above feto-maternal complications the most practical approach is to screen all pregnant women for hypothyroidism as early in pregnancy as possible (on before conception). In the case of the mother, screening would result in early diagnosis and treatment of hypothyroidism. The implications are staggering when one considers that there is a significant increase in intrauterine deaths, spontaneous abortions, premature births and pre-eclampsia in women with gestational hypothyroidism.
In the infant, major malformation and loss of IQ could be prevented by early diagnosis and treatment of the mother. It is believed that if screening of all pregnant women in implemented, the mother, the infant and society will all benefit.

Conclusion
A total of 107 patients were included in the study and were screened by estimation of serum TSH and FT4 to determine the presence of hypothyroidism. Only 100 women were followed up from their antenatal visit up till delivery Feto-maternal outcome of these patients was recorded, while 7 were dropped out because of early pregnancy loss. The salient observations made in this study are as follows:  The prevalence of hypothyroidism was 24.29% in this study.
 The present study concluded that history of recurrent pregnancy loss and diabetes are significantly associated with hypothyroidism.
 The study showed that there was increased rate of gestational hypertension, preeclampsia, preterm delivery and low birth weight babies in hypothyroid group which was statistically significant.
 The study also showed that rate of foetal distress during labour (47.36% Vs 30.86%) was also high and hence rate of emergency caesarean section (42.11 Vs 19.76%) was high in hypothyroid group. This value is also statistically significant.
 The study also showed that there was higher rate of still births, hyper bilirubinaemia and admission to neonatal ICU (foetal distress, meconium stained liquor) in the hypothyroid group.

What this study adds to existing knowledge
The present study therefore concludes that hypothyroidism continues to be an important medical condition in pregnancy with significant feto-maternal morbidity. This study therefore recommends that early identification and proper management of this condition is the only intervention to ameliorate and decrease is attendant morbidity and mortality.
Funding: Nil, Conflict of interest: Nil Permission from IRB: Yes