North American Registry of Midwives (NARM) Practice Exam

When is primitive placental circulation established?

1. Within the first week of gestation

2. In the first two weeks of gestation

3. After 4 weeks of gestation

4. By the end of the first trimester

The correct answer is: In the first two weeks of gestation

Primitive placental circulation is established in the first two weeks of gestation. During this period, critical developments occur that set the foundation for the placenta and its role in facilitating nutrient and gas exchange between the mother and the developing embryo. Initially, after fertilization, the embryo undergoes cleavage, leading to the formation of a blastocyst. As this structure implants into the uterine lining, it initiates the formation of the placenta. Early vascularization begins, allowing for the establishment of a primitive form of blood circulation that enables the embryo to start receiving essential nutrients and oxygen from maternal blood. This early circulation is crucial as it supports the rapidly growing embryo before the development of more complex and fully functional placental circulation, which will mature by the end of the first trimester. Understanding this timeline helps midwives and healthcare professionals recognize the critical stages of early pregnancy development and the importance of early prenatal care.