{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Human chorionic gonadotropin (hCG) fulfills dual roles in assisted reproductive technology. On one hand, when administered as an exogenous trigger to induce final oocyte maturation, hCG is used—either alone or alongside other agents such as GnRH agonists or kisspeptin—to optimize the retrieval of mature oocytes. Data indicate that follicles measuring between 12–19 mm on the day of trigger are most effective in yielding mature oocytes, regardless of the specific trigger used (see"}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "and."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n On the other hand, endogenous hCG levels, particularly those measured 21 days after embryo transfer ("}, {"type": "b", "children": [{"type": "t", "text": "hCG21"}]}, {"type": "t", "text": "), serve as a critical biomarker for early pregnancy evaluation. Measurement of hCG21 is integrated into mathematical models to accurately differentiate between intrauterine, ectopic, and biochemical pregnancies, thereby allowing clinicians to stratify patients according to risk and tailor management strategies accordingly."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": " In addition, early hCG assessments—such as those on day 14 post-transfer—have been incorporated into predictive models for ongoing pregnancy, bolstering early clinical decision-making."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Finally, when used alongside ultrasound, sensitive plasma hCG determinations aid in distinguishing normal intrauterine pregnancies from ectopic gestations, which is essential for prompt and accurate diagnosis."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": "\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Ali Abbara, Lan N Vuong, Vu N A Ho, et al. 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