system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
In fetal circulation, pulmonary vascular resistance is more than systemic vascular resistance. At which stage, it becomes normal to adult level?
assistant
The correct answer is  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.”