Regarding the placenta and chorion, which of the following statements is NOT true?& x20; - NORCET 9 Mains - 2025

NORCET 9 Mains - 2025

Obstetrics & Gynaecology

Hard

Appeared in: NORCET 9 Mains - 2025

Explanation

The statement is false because maternal and fetal blood do not mix directly.
A multi-layered structure called the placental barrier separates the two circulations.
Maternal blood in the intervillous space is in direct contact with the syncytiotrophoblast, the outermost layer of the chorionic villi.
The fetal capillaries are located deep within the villous core, separated from maternal blood by the syncytiotrophoblast, cytotrophoblast, and connective tissue.
This separation is essential for nutrient exchange while preventing maternal immune rejection of the fetus.

Option B: This statement is true. The chorion frondosum, also known as the 'leafy chorion,' is the part of the chorion that develops extensive villi and forms the fetal side of the placenta.
Option C: This statement is true. As the amniotic sac grows, it obliterates the chorionic cavity and fuses with the chorion laeve, forming the amniochorionic membrane. This fusion is typically complete by the end of the first trimester (around 12 weeks).
Option D: This statement is true. The decidua basalis is the portion of the maternal endometrium (decidua) that lies directly under the site of implantation and develops into the maternal side of the placenta.

Visual 1: Diagram - Cross-section of a chorionic villus. This visual should clearly label the layers of the placental barrier: syncytiotrophoblast, cytotrophoblast, villous stroma (connective tissue), and the fetal capillary with its endothelium, all surrounded by maternal blood in the intervillous space.
Visual 2: Diagram - Early placental development. This visual can show the blastocyst implanting into the decidua, with the differentiation of the chorion into the chorion frondosum (at the decidua basalis) and the chorion laeve. It should also illustrate the relationship between the amnion, chorion, and decidua.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and physiology of the placenta and fetal membranes as background academic context rather than a clinical decision trigger.
The integrity of the placental barrier is vital for a healthy pregnancy. It protects the fetus from the mother's immune system, which would otherwise recognize the fetus as foreign (due to paternal antigens) and mount an attack.
The barrier is selectively permeable, allowing passage of nutrients, oxygen, and maternal antibodies (IgG) while blocking most bacteria and large molecules. However, some viruses (like Rubella, CMV, Zika) and drugs can cross it, highlighting the importance of avoiding certain exposures during pregnancy.
Breaks in the placental barrier, which can occur during delivery or due to trauma, can cause maternal-fetal hemorrhage. This can lead to fetal anemia or, if the mother is Rh-negative and the fetus is Rh-positive, maternal sensitization and risk of hemolytic disease in future pregnancies.

How to Approach the Question

First, identify the negative framing of the question by spotting the keyword 'NOT'. This means you are looking for the one false statement among four options.
Systematically evaluate each statement based on your knowledge of placental and fetal membrane anatomy.
Recall the fundamental principle that maternal and fetal blood circulations are separate systems that exchange substances across a barrier.
For option A, consider the structure of a chorionic villus. Maternal blood is outside the villus, while fetal capillaries are inside. This implies a barrier must exist.
For options B, C, and D, recall the definitions of the key terms: chorion frondosum (fetal placenta), decidua basalis (maternal placenta), and amniochorionic membrane (fused amnion and chorion).
By confirming that statements B, C, and D are correct anatomical facts, you can deduce by elimination that statement A must be the incorrect one.

Concept Tested & Keywords

QviuFVMBYpFRtdKBeNR8bA