Which of the following is true regarding placenta formation?

DSSSB 14 August 2024

Obstetrics & Gynaecology

Easy

Appeared in: DSSSB 14 August 2024

Explanation

The formation of the discrete placenta, which involves the proliferation of the fetal chorion frondosum and maternal decidua basalis, begins around the 6th week of gestation.
This structural development is considered complete by the 12th week of gestation.
By the end of the first trimester (around 12 weeks), the placenta is fully functional and takes over the production of hormones (like progesterone) from the corpus luteum to maintain the pregnancy.
After 12 weeks, the placenta continues to grow in size and weight but its fundamental structure is already established.

Option B: This timeline is incorrect. Placental formation is completed by the 12th week; it does not begin at this time. The period from 12 to 28 weeks involves placental growth and maturation, not initial formation.
Option C: This timeline is incorrect. Formation begins much earlier than the 10th week and is completed long before the 36th week. The placenta is fully mature by the third trimester, not still forming.
Option D: This timeline is too early. While initial development of chorionic villi begins after implantation (around week 3-4), the formation of the discrete, complex placental organ is not complete by the 6th week.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Timeline of placenta formation during gestation as background academic context rather than a clinical decision trigger.
A properly formed placenta is essential for a healthy pregnancy. It facilitates the transfer of nutrients, oxygen, and antibodies to the fetus while removing waste products.
Defects in early placental development (placentation) are linked to serious pregnancy complications, including miscarriage, pre-eclampsia, and fetal growth restriction (FGR).
Nurses educate expectant mothers about the importance of the first trimester for both fetal and placental development, emphasizing factors like nutrition and avoiding teratogens.

How to Approach the Question

This is a factual recall question testing knowledge of a specific timeline in obstetrics.
First, identify the key concept: the timeframe for 'placenta formation'. Note the keywords 'begins' and 'completed'.
Recall that the first trimester (up to about 13 weeks) is the critical period for organogenesis, which includes the formation of the placenta as a discrete organ.
The end of the first trimester (around 12 weeks) is a key milestone where the placenta becomes fully functional and takes over hormone production from the corpus luteum. This helps anchor the 'completed by' date.
Evaluate each option against this knowledge. The 6th to 12th week window aligns with the establishment of the placenta as a distinct structure that is fully functional by the end of the first trimester.
Eliminate other options as they fall outside this established biological timeline.

Concept Tested & Keywords

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E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur p. 51-62