...is the child registered to the father?
The plenum of the Supreme Court of Ukraine defines a single mother as a woman who:
is not married and the child's birth certificate does not contain an entry about the child's father;
or the record about the father is made in the prescribed manner at the instruction of the mother (that is, from the words of the mother);
widow;
another woman who raises and supports the child herself.
If you meet one of the above criteria, then you can claim the status of a single mother. But keep in mind that the main criterion for determining the status of a single mother is: raising and maintaining a child without the father's participation. A woman receiving alimony from the child's father, running a joint household with him, removes the status of a single mother.