Changes

== Aetiology ==

== Aetiology ==

* Results from sexual modification of a '''female twin''' by the in-utero exchange of blood from a male fooetus.

* Results from sexual modification of a '''female twin''' by the in-utero exchange of blood from a male foetus.

* Freemartin is XX genetic female, but becomes an XX/XY chimera.

* Freemartin is XX genetic female, but becomes an XX/XY chimera.

* 90% of female calves born co-twin to a male will be freemartins.

* 90% of female calves born co-twin to a male will be freemartins.