The development of the respiratory system in the fetus<>begins<>at about 4 weeks
Between the 5th and the 12th weeks of pregnancy, while the fetus is growing and developing, nerve cells form in the digestive tract, beginning in the mouth  and finishing in the anus.
The development of the respiratory system in the fetus begins at about 4 weeks.
The development of the respiratory system in the fetus begins at about?