In fetal circulation, pulmonary vascular resistance is more than systemic vascular resistance. At which stage, it becomes normal to adult level?

By 2 months of age, pulmonary resistance may approximate adult levels. “Immediately after birth, the lungs expand with air, dropping the pulmonary vascular resistance; and as the placenta is disconnected from the systemic circuit, the systemic resistance nearly doubles. The pulmonary arterioles continue to change gradually. The media becomes thinner and the lumen becomes wider. Thus, the pulmonary vascular resistance falls, almost reaching adult levels by the time the child is close to 8 weeks of age.”