Same-sex couples who wish to have a child must have recourse to someone other than their regular sexual partner in order to conceive a child. There are different ways of conceiving children, i.e. through surrogacy, artificial insemination, in vitro fertilization, and new methods that are currently being developed.
Not all fertility clinics will assist same-sex couples to have children; there are concerns that role models of both sexes are not present in the home for the child, that there will be less parental input from the non-biological parent, and that the child will be unhappy at school because his peers will taunt him about his non-standard family.
In 1990 a British court ruled that no group of women could be excluded from assistance in reproduction. Private donor arrangements are not legally recognized, so the non-biological co-parent has no legal rights to the child.
According to UCLA Williams Institute School of Law:
"In 2016, an estimated 705,000 United States households were headed by a same-sex couple (1.1% of all coupled household), including 346,000 male same-sex couples and 359,000 female same-sex couples. Approximately half of these same-sex households included married couples (approximately 357,000); the remaining half (approximately 348,000) were unmarried cohabitating couples. In comparison, over 90% of different-sex (i.e., male/female) cohabitating couples were married.
Between 2014 and 2016, 16.2% of all same-sex couples, 8.1% of same-sex male couples and more than one in five same-sex female couples were raising children, with higher rates of childrearing among married same-sex couples. Based on 2016 household counts, there were an estimated 114,000 same-sex couples raising children in 2016, including 28,000 male same-sex couples and 86,000 female same-sex couples. Like male/female couples with children, the majority (68.0%) of same-sex couples with children were raising biological children. However, same-sex couples with children were far more likely than male/female couples with children to have an adopted child (21.4% versus 3.0%) and/or a foster child (2.9% versus 0.4%). Married male same-sex couples with children were the most likely of all couples with children to be raising adopted and foster children." (https://williamsinstitute.law.ucla.edu/publications/same-sex-parents-us/)
Many fertility clinics refuse fertility treatments, including sperm donation, to female same-sex couples on the grounds that they are fertile, and therefore do not need fertility treatments. It would be equivalent to asking for chemotherapy just to get your hair cut.
Social outrage at same-sex parenting stems from a presumption that the children may be sexually abused. Society forgets that a parent is a parent first and foremost.
A child of same-sex parents is very much a wanted child. There is no such thing as an unwanted pregnancy.