**Question:** The progesterone of choice for emergency contraception is:

A. Utrozest
B. Jadelle
C. Gestodene
D. Levonorgestrel

**Correct Answer:** D. Levonorgestrel

**Core Concept:** Emergency contraception is a method of preventing pregnancy immediately after unprotected sexual intercourse or failure of other contraceptive methods. Progesterone-only pills, such as emergency contraceptives, act by preventing ovulation and thickening cervical mucus to hinder sperm penetration. The progesterone of choice for emergency contraception is levonorgestrel, which is the active ingredient in the widely available over-the-counter emergency contraceptives.

**Why the Correct Answer is Right:** Levonorgestrel is a synthetic progestin with the chemical name 17α-ethinyl-19-nortestosterone. It has high potency and effectiveness in preventing pregnancy when given within 120 hours (5 days) after unprotected intercourse. Levonorgestrel's mechanism involves suppressing the hypothalamic-pituitary-ovarian axis, thereby inhibiting follicle maturation and ovulation.

**Why Each Wrong Option is Incorrect:**

A. Utrozest (Utrogestan) is a combination of two progestogens - drospirenone and utrogestan (a mixture of 17α-ethinylestradiol and uterozest). It is not the correct choice for emergency contraception.

B. Jadelle (a subdermal contraceptive implant) is a copper-norplant device that releases levonorgestrel and copper ions, which leads to a hormonal imbalance in the woman's body and prevents fertilization. However, it is not a progesterone-only agent and is not the correct choice for emergency contraception.

C. Gestodene is a progestin with a similar chemical structure to levonorgestrel but is not as potent and effective for emergency contraception. It has a lower efficacy rate compared to levonorgestrel.

**Clinical Pearl:** The correct choice for emergency contraception is a potent and effective progesterone agent, and levonorgestrel is the preferred option due to its high potency and efficacy.