Document Type : Original Article
Authors
1 Department of Obstetrics and Gynecology, Taleghani University Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran;Department of Obstetrics and Gynecology, Shahid Beheshti University of Medical Sciences
2 Department of Community Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Abstract
Keywords
Thyroid disorders are among the common endocrine
problems in pregnant women. It is now well
known that not only overt, but also subclinical hypothyroidism
(SCH) has adverse effects on maternal
and fetal outcome (
We therefore studied the thyroid function of pregnant women to know the prevalence of subclinical hypothyroidism.
This descriptive cross-sectional study was done on 3158 pregnant women in Taleghani Hospital in Tehran, Shahid Beheshti University of Medical Sciences from October 2008-March 2012. For all pregnant women in the first prenatal care and during routine laboratory workup, screening of thyroid function was done by TSH level in endocrine laboratory in Taleghani Hospital by the chemiluminescent immunoassay (Elecsys 2010, Hitachi, Diamond, Japan). If TSH level was >2.5 mIU/L in the first trimester or TSH >3 mIU/L in the second or third trimester, free T4 measurement was done by chemiluminescent immunoassay to know whether it is subclinical or overt hypothyroidism. If serum FT4 was in the normal range (0.8-1.7 ng/dl) SCH was diagnosed and if below the normal range, OH was the diagnosis.
Their demographic (maternal age, gestational age, parity) and clinical details were collected as part of routine antenatal care and were recorded. We asked the women about personal and family history of thyroid disease. Duration of gestation was calculated from last menstrual period and verified by ultrasonography. The Ethical Committee of Shahid Beheshti University of Medical Sciences approved this study and informed consent was taken from all participants. SPSS software version 20 were used for data analysis including t test.
The age of patients ranged from 17-38 years old with mean ± SD (27 ± 5) (
Distribution of patient age of overt and subclinical hypothyroidism in pregnant women in Tehran between 2008 and 2012
Age(Y) | Frequency | Percent | Cumulative frequency |
---|---|---|---|
18 | 12.2 | 12.2 | |
36 | 24.5 | 36.7 | |
61 | 41.5 | 78.2 | |
32 | 21.8 | 100 | |
147 | |||
Prevalence of overt and subclicinal hypothyroidism in pregnant women in Tehran (2008-2012)
Type of hypothyroidism | No.of patients | Prevalence |
---|---|---|
131(89.1%) | 4.15% | |
16(10.9%) | 0.5% | |
147(100%) | 4.65% | |
Most of the women with subclinical hypothyroidism were diagnosed in the first trimester and many women were undetected till the second and third trimesters (
According to table 3 there was a significant difference in mean age (about 3.5 years) of patients in overt and subclinical groups (p=0.02) .This means that universal screening is necessary because most of the pregnancies occur in young women.
Relationship between mean age and gestational age and type of hypothyroidism in pregnant women in Tehran (2008-2012)
Diagnosis | Age(Y) | Number of patients in each trimester | ||||
---|---|---|---|---|---|---|
Mean | SD | First | Second | Third | Total | |
26.85 | 4.989 | 76 | 31 | 24 | 131 | |
30.38 | 4.856 | 9 | 4 | 3 | 16 | |
27.24 | 5.079 | 85 | 35 | 27 | 147 | |
We found the prevalence of subclinical hypothyroidism to be 4.15%. According to the study by Casey et al. the prevalence of subclinical hypothyroidism during early pregnancy is common, affecting about 2.5% pregnant women (
This suggests that subclinical hypothyroidism is more common in Iranian pregnant women. Subclinical hypothyroidism during early pregnancy has been shown to be associated with impaired neuropsychological development of children and several other adverse outcomes, including preterm delivery, preeclampsia and increased fetal mortality (
There is a high percentage of pregnant women that reach second and third trimester of pregnancy with undiagnosed thyroid disease. It is therefore necessary to screen women with a serum TSH, if they are pregnant or deciding to become pregnant.