Approximate weight of the placenta at term?

Appeared in: KPSC Staff Nurse - 2018

Explanation

At term, the placenta's weight is approximately 1/6th of the baby's weight.
An average term placenta weighs about 500 grams, while an average term baby weighs about 3000 grams (3 kg).
The resulting ratio of 500g to 3000g simplifies to 1:6, making this the standard accepted approximation.

Option A: A ratio of 1/4th would imply a placental weight of about 750g for a 3kg baby. This is excessively heavy and considered abnormal, often suggesting pathology like severe maternal diabetes or placental edema.
Option C: A ratio of 1/7th would imply a placental weight of about 430g for a 3kg baby. While placentas can be this size, it is on the lower end of the normal range, and 1/6th is the more widely accepted average.
Option D: A ratio of 1/3rd would mean the placenta weighs 1000g for a 3kg baby. This is grossly abnormal and would indicate severe placental pathology, such as massive edema (hydrops placentae) or a tumor.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Placental to fetal weight ratio at term as background academic context rather than a clinical decision trigger.
The Placental-to-Fetal Weight Ratio (PFWR) is a crucial indicator of intrauterine health and placental efficiency. Nurses may be involved in the examination of the placenta post-delivery.
A high ratio (larger placenta) can be linked to maternal diabetes, anemia, or infections, indicating a less efficient placenta.
A low ratio (smaller placenta) is often associated with fetal growth restriction, pre-eclampsia, and other forms of placental insufficiency.

How to Approach the Question

This is a factual recall question testing knowledge of normal physiological parameters in obstetrics.
First, identify the core concept being asked: the relationship between placental weight and baby's weight at term.
Recall the standard average weights for a term infant and placenta. A term baby is approximately 3000g (3kg), and a term placenta is approximately 500g.
Calculate the ratio by dividing the baby's weight by the placenta's weight (3000 / 500 = 6) or by expressing it as a fraction (500/3000 = 1/6).
Compare this calculated ratio to the given options.
Select the option that matches the standard 1:6 ratio.

Concept Tested & Keywords

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

E6 Anatomy Grays 43e Vol 1 Part 3 p. 10-12

Practise the full KPSC Staff Nurse - 2018

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