The fetus makes breathing motions about 14 percent of the time, drawing amniotic fluid inside the lungs. The fetal respiratory rate can rise as high as inhale/exhale cycles per minute at 22 to 26 weeks. This rate changes according to maternal carbon dioxide (CO2) levels, strongly suggesting that the respiratory center in the brainstem of the fetus already detects and responds to changes in CO2 levels in the blood.

44  inhale/exhale cycles per minute

Explanation:

According to a  research carried out by Natale et al, 1988 on the  patterns of fetal breathing activity in the human fetus at 24 to 28 weeks of gestation using Ultrasonic evaluation under a continuous 24-hour observations showed that The fetus makes breathing motions about 14 percent of the time in order to draw amniotic fluid inside the lungs, of which the  respiratory rate can rise as high as 44 inhale/exhale cycles per minute at 22 to 26 weeks of which this rate can change in relation  to maternal carbon dioxide levels, causing the fetus's  respiratory center to respond to alterations in carbon dioxide levels as carried out by Connors et al, 1989 in the research  on the role of Control of fetal breathing in the human fetus together with the carbon dioxide role in the generation of human fetal breathing movements.