What is the primary mechanism of action of mifepristone when used for medical abortion?
It induces uterine contractions.
It acts as a prostaglandin analog.
It blocks progesterone receptors.
It inhibits folic acid synthesis.
The Correct Answer is C
Mifepristone is a synthetic steroid used for medical abortion. It works by antagonizing progesterone receptors, leading to decidual breakdown, cervical softening, and increased uterine sensitivity to prostaglandins. Progesterone is essential for maintaining pregnancy by stabilizing the endometrium and suppressing uterine contractions. Mifepristone is typically followed by misoprostol to induce uterine expulsion. Side effects include bleeding, cramping, nausea, and diarrhea. Contraindications include ectopic pregnancy, chronic adrenal failure, and long-term corticosteroid use.
Rationale for correct answer
3. Mifepristone blocks progesterone receptors, disrupting the hormonal support required to maintain the endometrial lining. This leads to decidual necrosis and detachment of the trophoblast. The question asks for the primary mechanism, which is receptor blockade, not downstream effects. This action initiates the abortion process before prostaglandins are administered.
Rationale for incorrect answers
1. Mifepristone does not directly induce uterine contractions. That role is fulfilled by misoprostol, a prostaglandin E1 analog given after mifepristone. While mifepristone increases uterine sensitivity to prostaglandins, its primary action is hormonal antagonism, not myometrial stimulation.
2. Mifepristone is not a prostaglandin analog. It is a steroidal compound that acts on hormone receptors, not prostaglandin pathways. Misoprostol, given after mifepristone, is the prostaglandin analog responsible for uterine contractions and cervical dilation.
4. Mifepristone does not inhibit folic acid synthesis. That mechanism is associated with drugs like methotrexate, which is used in ectopic pregnancy management. Mifepristone acts on progesterone, not folate metabolism, and has no antifolate properties.
Take home points
- Mifepristone blocks progesterone receptors to initiate medical abortion.
- Misoprostol is used after mifepristone to induce uterine contractions.
- Methotrexate inhibits folic acid synthesis and is used in ectopic pregnancy.
- Progesterone maintains pregnancy by stabilizing the endometrium and suppressing contractions.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Vacuum aspiration is a surgical method used for early pregnancy termination. It involves suction evacuation of uterine contents using a manual or electric vacuum source. It is most effective between 5 to 12 weeks gestation. The procedure requires cervical dilation, carries low risk of infection, and has a complication rate below 1%. It is contraindicated in ectopic pregnancy, coagulopathy, and severe pelvic infection. Compared to medical abortion, vacuum aspiration offers immediate completion and tissue confirmation.
Rationale for correct answer
1. Vacuum aspiration is most commonly used in the first trimester, specifically between 5 to 12 weeks gestation. At this stage, the uterine contents are soft and easily evacuated by suction. The question asks for the most common use, which aligns with early gestational termination where vacuum aspiration is standard.
Rationale for incorrect answers
2. In the second trimester, fetal size and ossification increase, making vacuum aspiration less effective. Dilation and evacuation (D&E) becomes the preferred method due to the need for forceps and ultrasound guidance. Vacuum aspiration is not routinely used beyond 12 weeks due to incomplete evacuation risks.
3. During the third trimester, termination is rare and legally restricted. Methods include induction abortion or cesarean delivery, not vacuum aspiration. The fetal size and viability make suction techniques inappropriate and unsafe. Vacuum aspiration is contraindicated due to high risk of uterine rupture and maternal morbidity.
4. Post-term pregnancy refers to gestation beyond 42 weeks, where termination is managed by labor induction or cesarean section. Vacuum aspiration has no role in post-term management. The uterus is large, the fetus is viable, and suction evacuation is neither effective nor safe.
Take home points
- Vacuum aspiration is preferred for abortion between 5 to 12 weeks gestation.
- D&E is used for second trimester termination due to fetal size.
- Third trimester termination requires induction or cesarean delivery.
- Post-term pregnancy is not managed with vacuum aspiration.
Correct Answer is C
Explanation
Dilation and Evacuation (D&E) is a surgical technique used for second-trimester pregnancy termination. It involves cervical dilation, evacuation of uterine contents, and use of suction and forceps. It is preferred between 14 to 24 weeks due to fetal size and ossification. Risks include hemorrhage, uterine perforation, and infection. Cervical preparation with osmotic dilators or misoprostol is essential to reduce trauma. D&E is contraindicated in viable pregnancies and requires ultrasound guidance for safety.
Rationale for correct answer
3. D&E is the standard method for termination between 14 to 24 weeks gestation due to increased fetal size and calcification. At this stage, suction curettage alone is insufficient, and forceps are needed for complete evacuation. The question asks for the gestational age range where D&E is typically used, which aligns precisely with this window.
Rationale for incorrect answers
1. D&E is not used for pregnancies less than 6 weeks. At this early stage, the gestational sac is small and easily removed by manual vacuum aspiration or medical abortion using mifepristone and misoprostol. Surgical instrumentation is unnecessary and increases risk without benefit.
2. Between 6 to 10 weeks, suction curettage or medical abortion is preferred. The uterine contents are soft and easily evacuated without the need for forceps. D&E is excessive and not standard practice in this gestational range.
4. Beyond 28 weeks, termination is legally and ethically complex and typically involves induction abortion or cesarean delivery. D&E is contraindicated due to fetal viability and increased risk of uterine rupture and maternal morbidity. Surgical evacuation at this stage is rarely performed and not considered standard.
Take home points
- D&E is preferred for pregnancy termination between 14 to 24 weeks.
- Earlier gestations use suction curettage or medical abortion.
- Beyond 28 weeks, induction or cesarean is used due to fetal viability.
- Cervical preparation is essential before D&E to prevent trauma.
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