Serum human chorionic gonadotropin (hCG) levels were measured on day 14, and TVS was performed 4 weeks after ET. Clinical pregnancy was diagnosed if a gestational sac was observed, and a viable pregnancy was confirmed when cardiac activity was detected. If more than one gestational sac was foun...
As hCG stimulates the thyroid to produce more free thyroxine (FT4), which may lead to decreased thyroid-stimulating hormone (TSH) levels, the reference ranges of thyroid-related indicators may differ between singleton and twin pregnancies in the first trimester. This study aimed to establish ...