患者　 2 4岁 ,第一胎。末次月经 1996年 3月 2 3日 ,预产期同年 12月 30日 ,平时月经周期 (5 / 15～ 30 )天 ,量中 ,无痛经史。于停经 46天有早孕反应 ,孕 3+月阴道出血 2天。Ｂ超提示 :宫内妊娠 ,前置胎盘。孕 4+月Ｂ超复查同上 ,孕 5月觉胎动 ,孕 2 3+3 周首次产前检查。测 Patient 24 years old, first child. The last menstrual March 23, 1996, the expected date of birth on December 30 the same year, the usual menstrual cycle (5/15 ~ 30) days, the amount of no history of dysmenorrhea. 46 days in menopause have early pregnancy reaction, vaginal bleeding 3+ months 2 days. B-Tip: intrauterine pregnancy, placenta previa. Pregnancy 4+ month B-ultrasound review Ibid, pregnancy in May feel fetal movement, pregnancy 23 +3 weeks first prenatal examination. Measurement