A study of over 3,700 people in China found that carrying hidden gene variants is common. Certain variants found mainly in East Asians significantly influence the chance that both partners carry the same condition. Screening based only on global data may miss these variants. Incorporating population-specific information can therefore provide a clearer picture for genetic counseling and family planning. (https://jmg.bmj.com/content/early/2026/04/03/jmg-2025-111273)