Early pregnancy is maintained by

Appeared in: UPPSC 2017

Explanation

The corpus luteum is a temporary endocrine structure formed from the ovarian follicle after ovulation.
If fertilization occurs, the developing embryo produces human chorionic gonadotropin (hCG).
hCG 'rescues' the corpus luteum, stimulating it to produce progesterone, which is vital for maintaining the uterine lining (endometrium) in early pregnancy.
This function is critical for the first 7 to 10 weeks of gestation, until the placenta is mature enough to take over hormone production.

Option A: The placenta becomes the primary source of progesterone only after the first trimester, a process known as the luteal-placental shift.
Option C: The breasts undergo changes during pregnancy to prepare for lactation, but they do not produce the hormones necessary to sustain the pregnancy itself.
Option D: A Graafian follicle is the structure that contains the egg before ovulation. After ovulation, it transforms into the corpus luteum.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal maintenance of early pregnancy as background academic context rather than a clinical decision trigger.
Understanding this hormonal pathway is crucial for managing threatened abortions and patients with a history of recurrent miscarriages. Progesterone supplementation (luteal phase support) is a common intervention in these cases.
Measurement of serum hCG is the basis for modern pregnancy tests. Serial hCG levels are often monitored to assess the viability of an early pregnancy.
What if? - A patient has a 'luteal phase defect,' where the corpus luteum produces insufficient progesterone. This can prevent proper implantation or lead to early pregnancy loss because the uterine lining is not adequately maintained. Treatment often involves administering exogenous progesterone.

How to Approach the Question

First, identify the key phrase in the question: 'Early pregnancy'. This specifies the time frame is the initial weeks after conception.
Next, recall the sequence of hormonal events following fertilization. The embryo must send a signal to the mother's body to prevent menstruation.
Evaluate each option's role in the reproductive cycle. The Graafian follicle releases the egg. The breast prepares for lactation. The corpus luteum and placenta both produce progesterone.
Differentiate the timing of the roles of the corpus luteum and the placenta. The corpus luteum is the primary source of progesterone immediately after conception, stimulated by hCG.
Conclude that the corpus luteum is responsible for maintaining early pregnancy, while the placenta takes over this role later.

Concept Tested & Keywords

Q791KUrCAfh7QbQC70LoM0

E6 Medicine Harrison 22e Part 2 p. 1033-1035

E6 Physiology Guyton 4SAE Part 3 p. 60-62

E6 Obstetrics Williams p. 38-57

Practise the full UPPSC 2017

Attempt every question from this paper in a timed mock, then review the full solution for each one.