This case study was conducted to explore the concern and adaptative behaviors of a multifetal woman during the first trimester of assisted reproduction. Data was collected through participant observation from the fourth week of the pregnancy to the twelfth week. Content analysis was used to analyse behavior records. The findings revealed that the woman's concern behaviors were directed towards three aspects:the mother herself, the fetus, and medical management. Mother-related concerns included presumptive signs and positive signs of pregnancy, and physical functions of continuing the pregnancy to term. Fetus-related concerns included fetal number, gender, fetal growth, and health status. Medical management concerns included gencral examination and multifetal pregnancy management. The woman's adaptative behaviors included:(1)affirmation-seeking behaviors,(2)accommodation behaviors,(3)affection adaptation behaviors. Affirmation-seeking behaviors are divided into proving and identifying behaviors. Accommodation behaviors are divided into conserving and complying behaviors. Affetion adaptation behaviors included reliance, isolation, lower expectation and repeat description.