An additional factor is the present possibility of determining the sex of the baby before birth and the future possibility of choosing the sex of the baby before conception. These possibilities may lead to some advantages - the eradication of sex-linked genetic disorders, for example, such as haemophilia, some enzyme deficiency diseases and a form of muscular dystrophy, all of which are many times more common among males than among females. But because of the increasing availability of legal abortion and the widespread preference in many cultures for the birth of sons rather than daughters, some demographers fear that the sex ratio may be further imbalanced by abortion of female foetuses and the choice to conceive sons.