Study site and subjects
A hospital-based case-control study was conducted in Pingguo County,
Guangxi, China.
Pingguo County is located in in the southern of China, which is an
iodine-sufficient area and a suitable research site for thyroid
dysfunction.
Participants were recruited from the population of pregnant women during
their routine inspection in Pingguo Maternal and Child Health Hospital
from May 2017 to August 2018. The hospital provides service for pregnant
women and children. This study was approved by the Medical Research
Ethics Committee of the local Maternity and Child Health Hospital, and
all the women involved in this study gave informed consent.
Pregnant women aged 18 - 46 years who lived in Pingguo for more than 6
months and only screened in the second trimester (gestational age
between 14 and 27 weeks) were invited to participate in the study. The
exclusion criteria were as follows: 1) pregnant women with a history of
thyroid disease, such as Christine disease; 2) pregnant women with a
family history of mental retardation or organic mental disorder and
dementia, hereditary endocrine and metabolic diseases, cancer,
congenital malformations, and developmental dysplasia;
3) pregnant women addicted to the
drugs and/or alcohol; 4) pregnant women lived in Pingguo County less
than 6 months; 5) pregnant women with communicable diseases, including
HIV, tuberculosis and HBV; and 6) those withholding consent to
participate. In this study, 550 eligible pregnant women (gestational age
ranging between 14 and 27 weeks) were recruited from May 2017 to August
2018.