<p>The language used in educational settings plays a fundamental role in shaping and internalizing societal gender notions. Consequently, the presentation of scientific knowledge in schools may unintentionally reinforce social inequalities and biases. Critical analyses within science education on the topic of fertilization have demonstrated that gender stereotypes are often projected onto gametes: female gametes are frequently depicted as slow, passive, and invisible, while sperm are portrayed as active, strong, and fast. To investigate this further, a qualitative study was conducted. Considering the well-documented gender biases in teaching human fertilization and in students’ ideas about it, we designed and implemented instructional interventions to enrich students’ conceptual understanding of human fertilization and to foster a more gender-inclusive approach. We analyzed Mexican high school students’ (<i>N</i> = 121) descriptions of human fertilization both before and after intervention, aiming to characterize these descriptions and identify potential shifts in gender biases about this topic. Conducted in three phases—design of the teaching sequence, implementation, and data analysis—the study revealed that the metaphor of fertilization as a “race” is not only scientifically inaccurate but also frequently adopted by students. This is problematic as the portrayal of sperm as persistent, determined “fighters,” contrasted with eggs depicted as passive or difficult to reach, reinforces stereotypes of active male dominance and female passivity in reproductive processes. Although this metaphor may simplify fertilization for educational purposes, it ultimately distorts scientific understanding and perpetuates gender biases.</p>