Using Mifepristone, therapeutic abortion can be effectively induced until______ weeks of gestation?
First, I need to recall what mifepristone does. Mifepristone is an antiprogestin, right? It blocks progesterone receptors, which are essential for maintaining the uterine lining during pregnancy. Without progesterone's action, the lining breaks down, leading to abortion. Then there's misoprostol, which is usually used in combination with mifepristone to induce contractions and cervical dilation.
The key point here is the gestational age limit. I remember that the combination of mifepristone and misoprostol is effective up to a certain week. I think it's up to 10 weeks. Wait, but some sources might say 9 weeks. Let me double-check. The FDA approved it up to 10 weeks, but in some countries, guidelines might differ. However, the standard answer in exams like NEET PG or USMLE is usually 10 weeks. So the correct answer here is probably 10 weeks, which would be one of the options.
Now, the options aren't given, but the correct answer is likely 10 weeks. The other options might be numbers like 6, 8, 12, or 14. Let's say the options are A. 6, B. 8, C. 10, D. 12. Then the correct answer is C.
Why is it 10 weeks? Because beyond that, the placenta is more firmly implanted, and the effectiveness decreases. Also, the risk of complications increases. So the mechanism of action is more effective in early pregnancy.
For the wrong options: 6 weeks is too early; the method is effective beyond that. 8 weeks is within the effective range but not the upper limit. 12 weeks is beyond the limit, so mifepristone alone isn't effective, but the combination might still work in some cases up to 12, but the standard is 10. So the answer should be 10 weeks.
**Core Concept**
Mifepristone induces abortion by competitively inhibiting progesterone receptors, preventing corpus luteum maintenance and endometrial support. Its efficacy is time-sensitive due to placental progesterone production, which becomes dominant after a specific gestational age.
**Why the Correct Answer is Right**
Mifepristone combined with misoprostol is FDA-approved for medical abortion up to **10 weeks** of gestation. Before 10 weeks, the corpus luteum is the primary source of progesterone, making it susceptible to mifepristone. Beyond this, placental progesterone synthesis dominates, reducing the drug’s effectiveness. The regimen achieves >95% success until ~10 weeks, after which surgical methods are preferred.
**Why Each Wrong Option is Incorrect**
**Option A: 6 weeks** – Mifepristone is effective beyond 6 weeks; this underestimates its therapeutic window.
**Option B: 8 weeks** – While effective at 8 weeks, this is not the upper limit of efficacy.
**Option D: 1