First off, I am NOT a lawyer or anything close. Did you search the internet? The following were the first couple things I found.
Hope your not in Kansas or any other place on Earth where there might be lawyers, or governments. Here is a link for one case in Kansas where the women even told the state that he shouldn't be responsible because they all signed an agreement, but the state saw differently.
http://www.cnn.com/2014/01/23/justic...perm-donation/
It really would depend on your country and/or state. Some states do have a clause for it, but ONLY if a physician was involved for artificial insemination.
Sperm Donor Protection: The Uniform Parentage Act
About two-thirds of states have adopted the Uniform Parentage Act (UPA), which gives protections to sperm donors in cases where a mother has sued them for child support. The 1973 version of the UPA provides that any man that gives his sperm to a physician for purposes of artificially inseminating someone other than his wife is not the legal father of the child borne out of the insemination. Since the donor is not the legal father, he is not legally bound to pay child support. However, these protections are limited, as the states that have adopted the 1973 version of the UPA have generally not been willing to extend these protections to a donor when there has not been a physician involved in the insemination process. For example, if the insemination takes place at home, even without intercourse, if a physician was not involved in the process, the donor is not protected by this law.
http://family-law.freeadvice.com/fam...obligation.htm
Just in case you wanted to know, you can go to google.com and put this in for the search; "sperm bank sue for child support"