How old is the 12-week fetus?

At 12 weeks of pregnancy, the size of the fetus should be 12 cm in head and arm length, 9-10 cm in length and about 14 g in weight. At this time, the fetus has developed perfectly. Through abdominal B-ultrasound examination, fetal limb activities can be observed; however, the growth and development of the fetus will be affected by the menstrual cycle and vary.