This has been bugging me lately...those anatomy scans determine your baby's SEX, not the gender. Gender is a social thing. See below:
Sex refers to the biological distinction between males and females; by contrast, gender concerns the social differences between males and females. Research in sociology focuses on gender rather than sex; sociologists distinguish between sex and gender to study differences between human males and females with greater precision. Whereas sex is based on physical differences, gender is based on social factors such as values, perceptions, beliefs, and attitudes. For example, men and women have different genitalia; this is a difference of sex. Men and woman also face different social expectations, as when women are expected to be more nurturing than men; this is a difference of gender. Gender varies across time and culture, as different groups have different beliefs about appropriate behavior for males and females.