Limb buds start to form cartilage, which will become bone. Paddle-like hands and feet emerge from developing arms and legs. Inner ear develops.
At roughly 2 cm long, the heart has been beating for three weeks. The foetus’ body begins to respond to touch (proprioception develops); although the mother will not be able to feel movement until the fourth or fifth month. Gums are formed. Nerves spread through the body, connecting to each other and to muscles, eyes, ears, etc.
Facial bones are formed. External genitals begin to form. Fingers and toes separate. Eyelids close until week 28 to protect developing eyes. The foetus begins to kick, stretch, and hiccup (as the diaphragm develops), but the movement cannot be felt yet.
Reflexes develop – fingers open and close, toes curl, and opening and closing the mouth. Peach-fuzz hair begins to grow on the skin. All the organs, muscles, limbs and bones are in place, and the sex organs are well developed.
Baby’s ear at 14 weeks.
At 16 weeks, the baby is approximately 14 cm tall and only 170 g in weight. Eyebrows, eyelashes, and fine hair appear. The child can grasp with his hands, kick, and even somersault. Fingerprints are forming.
The fetus now sleeps, awakens, and exercises its muscles energetically. Fingernails appear. Sex organs are visible using an ultrasound device (the doctor can tell if it is a boy or a girl).
Footprints and fingerprints have formed. Though still small and fragile, the baby is growing rapidly and could possibly survive if born at this stage.
Hearing, smell, and touch are now developed and functioning. The heartbeat can now be heard through a stethoscope. More and more fat appears under skin, increasing the foetus’ weight.
All bones, except in the skull, continues to harden. Skin becomes softer, plumper, and less wrinkly, transparent, and red. Ability to see color red develops (first color seen).
Full-term but continues to build fat layer for temperature regulation after birth.