We know there are birthmothers in this community, but are there birthfathers?
The novel doesn't indicate that birth-fathers' identites are known as the whole pregnancy and birth process is a laboratory procedure.
I would assume that the whole process of fertilization is handled in the lab through in vitro fertilization. Perhaps the birthmothers are surrogates with no physical relationship to the fetus that they carry.
Depending on one's station in this society, they would select the characteristics that are desirable from various groups in the society.
I think this is a "hole" in the book that leaves plenty of room for speculation on the part of the reader. And, are the birthmothers selected for their good genetic qualities?
The novel doesn't indicate that there are "birth fathers," but we would assume that all of the positions required to maintain the community are not mentioned in the book. The indication is that the pregnancy of a birth mother is handled in a laboratory. At the first sign of hormone release, or a male and female showing interest in each other the young people are given a "pill" to stop the production of the hormones. There is no sexual desire, and no need for sexual intercourse. The sperm are more than likely harvested and implanted into the birth mother. The biological parentage of each child born is never reveled.