Chorionic sac at 13^th week. Smooth chorion is formed by gradual degeneration and disappearance of the chorionic villi. Villus chorion maintains its chorionic villi and ultimately gives rise to placenta. Placenta is a lobulated structure which contains cotyledons. Blood circulates through the intervillous spaces of the cotyledons.

A 13 week fetus. The crown to rump length is 82 cm. At this stage, still the eyelids are fused.

A 17 week fetus. Although it appears mature, a fetus at this stage is unable to survive if it aborts spontaneously, as in this case.

A 25 week fetus (Fetal position). Skin has a wrinkled appearance and the subcutaneous fat is minimal at this stage.

A 29 week fetus (Cephalic presentation). To view the fetus, the anterior wall of the uterus and its membranes are folded back. At this stage, the fetus has rotated so that its head is at the cervix of the uterus and its buttock is towards the fundus of the uterus.

A 36 week fetus. At this stage, the skin has developed sufficient amount of subcutaneous fat.