Chief source of progesterone during pregnancy is?

ESIC Nursing Officer 2016 (Shift -2)

Obstetrics & Gynaecology

Medium

Appeared in: ESIC Nursing Officer 2016 (Shift -2)

Explanation

The placenta is the primary endocrine organ responsible for hormone production for the majority of the pregnancy.
After the first 8-10 weeks, a critical event called the 'luteal-placental shift' occurs, where the placenta takes over progesterone synthesis from the corpus luteum.
From the end of the first trimester until delivery, the placenta produces increasingly large amounts of progesterone, reaching approximately 250 mg per day.
This massive production of progesterone is essential for maintaining uterine quiescence, preventing premature contractions, and supporting overall pregnancy health.

Option A: The ovary as a whole is not the primary source. It contains the corpus luteum, which is only the main source in the very early stages of pregnancy.
Option B: The adrenal cortex produces various steroid hormones, but its contribution to progesterone levels during pregnancy is minimal compared to the placenta.
Option D: The corpus luteum is the chief source of progesterone only for the first 8-10 weeks of pregnancy. The question asks for the chief source during the entire pregnancy, for which the placenta's contribution is far greater in both duration and volume.

Visual 1: Graph - A line graph showing progesterone levels throughout the 40 weeks of gestation. The graph should clearly label the initial production by the corpus luteum, the crossover point of the 'luteal-placental shift' around 8-10 weeks, and the steep, continuous rise in production by the placenta until term.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Sources of progesterone production during pregnancy as background academic context rather than a clinical decision trigger.
Understanding the luteal-placental shift is critical in early pregnancy management. Patients who undergo surgical removal of the corpus luteum (e.g., for an ovarian cyst) before 10 weeks' gestation require progesterone supplementation to prevent miscarriage.
Progesterone is often called the 'hormone of pregnancy' because it relaxes the uterine muscle, preventing premature contractions. Low progesterone levels can be a factor in recurrent pregnancy loss.
What if? If a patient on an IVF cycle has her corpus luteum function suppressed by medications, she will be prescribed exogenous progesterone support from the time of embryo transfer until the placenta is producing enough on its own, typically around 10-12 weeks gestation.

How to Approach the Question

First, analyze the question to identify the key terms: 'chief source' and 'during pregnancy'. 'Chief' implies the largest or most important source, and 'during pregnancy' refers to the entire gestational period.
Recall the timeline of hormonal production in pregnancy. Remember that there are two main sources of progesterone at different times.
Compare the roles of the corpus luteum and the placenta. The corpus luteum is essential early on, but its function is temporary.
The placenta takes over and produces progesterone for a much longer period (from ~10 weeks to term) and in much greater quantities.
Conclude that because the placenta's contribution is larger and spans most of the pregnancy, it is the 'chief source' overall.

Concept Tested & Keywords

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