**Core Concept**
Natural family planning (NFP) methods, also known as fertility awareness-based methods (FABMs), are non-hormonal, non-invasive techniques used to achieve or prevent pregnancy. These methods involve tracking the body's natural cycles to determine periods of fertility and infertility.

**Why the Correct Answer is Right**
Natural family planning methods rely on understanding the menstrual cycle, ovulation, and cervical mucus changes. Women with regular cycles can use basal body temperature (BBT), cervical mucus observations, or a combination of both to identify fertile and infertile windows. This approach requires a high level of self-awareness and commitment to tracking body changes.

**Why Each Wrong Option is Incorrect**
**Option A:** While barrier methods like condoms do prevent pregnancy, they are not considered NFP methods as they physically block sperm rather than relying on natural cycle tracking.
**Option B:** Hormonal contraceptives, such as the pill or patch, regulate ovulation and prevent pregnancy through hormonal manipulation, which is distinct from NFP methods.
**Option C:** IUDs (intrauterine devices) are a form of long-acting reversible contraception that prevents pregnancy through mechanical means, not by tracking natural cycles.

**Clinical Pearl / High-Yield Fact**
It's essential to note that NFP methods require a high level of commitment and self-awareness, and may not be as effective as hormonal or barrier methods in preventing pregnancy. However, they can be a valuable option for individuals who prefer non-invasive, non-hormonal methods or have specific medical or personal reasons for avoiding other forms of contraception.

**Correct Answer: D. Natural family planning (NFP) methods, also known as fertility awareness-based methods (FABMs), are non-hormonal, non-invasive techniques used to achieve or prevent pregnancy.**