At 12 weeks, a baby is about the size of a plum or a lime, with an average length of approximately 2.1 to 2.5 inches (5.4 to 6.4 cm) from head to bottom (crown to rump). The baby typically weighs around 0.49 ounces (14 grams) at this stage.
The baby is fully formed with functioning organs, muscles, limbs, and bones beginning to ossify. Reflexes such as opening and closing fingers, curling toes, and even responding to touch are developing by this time.
