Drugs in pregnancy: all-or-none period: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · Drugs in pregnancy: all-or-none period

Sample item

A woman takes a known teratogen in the first week after conception, before she knows she is pregnant. According to the principles of teratology, what is the most likely outcome?

ASpecific limb malformationsBEither loss of the conceptus or normal developmentCGrowth restriction in the third trimesterDCardiac septal defects only

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Either loss of the conceptus or normal development

During the first two weeks after conception, before organogenesis, an insult usually either kills the embryo or is repaired by the totipotent cells, which is the all-or-none effect. Structural malformations are most likely when exposure falls within organogenesis, from about the third to the eighth week.

Option by option

A. Specific limb malformations
Limb malformations arise from exposure during limb development in organogenesis.
B. Either loss of the conceptus or normal development (correct)
Correct. Pre-implantation exposure gives an all-or-none outcome.
C. Growth restriction in the third trimester
Growth restriction results from exposure later in gestation, in the fetal period.
D. Cardiac septal defects only
Cardiac defects arise from exposure during heart formation in organogenesis.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Either loss of the conceptus or normal development. During the first two weeks after conception, before organogenesis, an insult usually either kills the embryo or is repaired by the totipotent cells, which is the all-or-none effect.

Why is "Specific limb malformations" not the answer?

Limb malformations arise from exposure during limb development in organogenesis.

Why is "Growth restriction in the third trimester" not the answer?

Growth restriction results from exposure later in gestation, in the fetal period.

Why is "Cardiac septal defects only" not the answer?

Cardiac defects arise from exposure during heart formation in organogenesis.

What concept does this question test?

It tests Drugs in pregnancy: all-or-none period in Pharmacology. Structural malformations are most likely when exposure falls within organogenesis, from about the third to the eighth week.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Drugs in pregnancy: all-or-none period?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.