## Core Concept
Fibroids, also known as uterine leiomyomas, can impact fertility and pregnancy outcomes. The underlying reasons involve alterations in the uterine environment that affect implantation and maintenance of pregnancy.

## Why the Correct Answer is Right
The correct answer, **C. distortion of uterine cavity**, is right because fibroids can cause significant changes in the uterine cavity's shape and lining, affecting implantation of the embryo. This distortion can lead to difficulties in conception and increased risk of miscarriage. The mechanism involves both mechanical disruption of the uterine cavity and possible alterations in local factors that support implantation.

## Why Each Wrong Option is Incorrect
- **Option A: Production of hormones** - While fibroids may produce some factors, their primary impact on infertility and pregnancy wastage isn't through hormone production but through mechanical and possibly biochemical effects on the uterine environment.
- **Option B: Interference with ovulation** - Fibroids do not directly interfere with ovulation; their impact on fertility is more related to the uterine environment rather than ovarian function.
- **Option D: Interference with sperm transport** - Fibroids can affect the uterine cavity and possibly the fallopian tubes if they are large, but interference with sperm transport is not the primary mechanism by which they cause infertility and pregnancy wastage.

## Clinical Pearl / High-Yield Fact
A key point to remember is that submucosal fibroids, which grow into the uterine cavity, have a more significant impact on fertility and pregnancy outcomes compared to intramural or subserosal fibroids. The presence of fibroids, especially those distorting the uterine cavity, is a consideration in the evaluation of infertility.

## Correct Answer: C. distortion of uterine cavity.