In which gestational age the Chronic villus sampling (CVS) can be performed trans-cervically?

DHS 2018 shift 1st

Obstetrics & Gynaecology

Easy

Appeared in: DHS 2018 shift 1st

Explanation

Chorionic Villus Sampling (CVS) is a prenatal diagnostic test that is typically performed between 10 and 13 weeks of gestation.
This time frame provides the benefit of an early diagnosis, allowing parents more time for decision-making.
Performing the procedure within this window is crucial for safety, as conducting it before 10 weeks is associated with a significantly increased risk of fetal limb-reduction defects.
The 10-12 week option falls perfectly within this established safe and effective period for CVS.

Option A: Performing CVS at 7-9 weeks is contraindicated due to a well-documented and unacceptably high risk of causing severe fetal anomalies, specifically oromandibular limb hypogenesis and limb-reduction defects.
Option C: This gestational age is the standard window for performing amniocentesis, not CVS. By 16-18 weeks, the amniotic sac is well-developed, making amniocentesis the preferred and safer procedure for genetic testing.
Option D: This is too late in the pregnancy for CVS. If genetic testing is required at this advanced stage, amniocentesis or fetal blood sampling (cordocentesis) would be the appropriate diagnostic tools.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Optimal gestational age for Chorionic Villus Sampling (CVS) as background academic context rather than a clinical decision trigger.
A key nursing role is to ensure the patient understands the risks (miscarriage, infection, limb defects if done too early) and benefits (early diagnosis) before providing informed consent for CVS.
Nurses must verify the patient's Rh status. If the mother is Rh-negative, it is critical to ensure Rho(D) immune globulin is administered after the procedure to prevent isoimmunization.
Accurate gestational age dating is paramount before scheduling a CVS to ensure the procedure is performed within the safe 10-13 week window.

How to Approach the Question

First, identify the core subject of the question, which is the timing of a prenatal procedure. Note the typo "Chronic" and recognize it as "Chorionic" Villus Sampling (CVS).
Recall the two main invasive prenatal diagnostic tests: CVS and amniocentesis.
Remember the key difference in their timing: CVS is performed earlier in pregnancy than amniocentesis.
This knowledge allows you to eliminate the later gestational age options (16-18 weeks and 20-22 weeks), as they are more typical for amniocentesis.
Now, compare the two early options: 7-9 weeks and 10-12 weeks.
Consider the principle of fetal safety. Procedures performed very early in organogenesis often carry higher risks. Recall or deduce that CVS has a known risk of limb defects if performed too early.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 37-56

E6 Midwifery Obstetrics and Gynecology Nursing Sandeep Kaur p. 52-63