Endometrium in pregnancy is known as:
A. Decidua
B. Decubitus
C. Trophoblast
D. Gravid endometrium
Correct Answer: A. Decidua
Explanation: The endometrium in pregnancy is known as the decidua.
After implantation of the fertilized ovum, the endometrial tissue undergoes significant changes (decidualization) and is then called the decidua . It is divided into three parts:
• Decidua basalis : the part beneath the implanted embryo that forms the maternal portion of the placenta.
• Decidua capsularis : the part that covers the embryo and later fuses with the decidua parietalis.
• Decidua parietalis (or decidua vera): the remaining endometrium lining the rest of the uterine cavity.
So, the correct and most precise answer is: decidua.
Other Options Details are given below 👇
Here are clear, concise descriptions of all the options (commonly encountered in obstetrics, gynecology, and placental pathology):
A. Decidua
• The modified endometrium (inner lining of the uterus) during pregnancy.
• It is the maternal part of the placenta.
• Divided into three subtypes:
• Decidua basalis (under the implanted blastocyst, forms the maternal part of the placenta)
• Decidua capsularis (covers the conceptus, later fuses with decidua parietalis)
• Decidua parietalis (the rest of the uterine lining not involved in placental formation)
• Rich in glycogen and undergoes decidual reaction (large, pale, epithelioid cells).
B. Decubitus
• This term is unrelated to pregnancy.
• It means “lying down” (from Latin decumbere).
• Commonly used in medicine as decubitus ulcer = pressure ulcer or bed sore (skin and tissue damage caused by prolonged pressure, usually in bedridden patients).
• In multiple-choice questions involving pregnancy/placenta, “decubitus” is usually a distractor (wrong option) because it sounds similar to “decidua” but has nothing to do with it.
C. Trophoblast
• The outer layer of cells of the blastocyst (early embryo).
• Fetal in origin (not maternal).
• Responsible for implantation and formation of the placenta.
Differentiates into:
• Cytotrophoblast (inner cellular layer) Syncytiotrophoblast (outer multinucleated syncytium that invades the decidua and produces hCG)
– Forms the fetal part of the placenta (chorionic villi, chorionic plate, etc.).
D. Gravid endometrium
• Literally means “pregnant endometrium.”
• General term for the uterine lining (endometrium) during pregnancy.
• The gravid endometrium is essentially the same as the decidua (the term “decidua” is the more specific and widely used medical term for the transformed gravid endometrium).
• So, “gravid endometrium” = decidua (decidua is the preferred term in modern obstetrics and pathology).
Summary for quick recall (especially in exams)
• Maternal component of placenta → Decidua (A) or gravid endometrium (D) – both correct in different wording
• Fetal component of placenta → Trophoblast (C)
• Completely unrelated distractor → Decubitus (B) – means pressure ulcer
Most questions asking “maternal part of placenta” accept decidua as the answer; “gravid endometrium” is sometimes used synonymously.
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Authors & Editor: GS India Academy Team.