Anembryonic gestation
（重定向自Blighted ovum）
An anembryonic gestation (also known as a blighted ovum) is a pregnancy in which the very early pregnancy appears normal on an ultrasound scan, but as the pregnancy progresses a visible embryo never develops or develops and is reabsorbed. In a normal pregnancy, an embryo would be visible on an ultrasound by six weeks after the woman's last menstrual period.