Private health insurance asks a different question. It does not ask whether there is a marriage certificate, but which partner has the illness. Organic infertility is an illness within the meaning of the insurance conditions, and its treatment is medically necessary treatment under § 1 (2) MB/KK. If the cause lies with the privately insured person, their plan reimburses the treatment under the cause principle, including the treatment steps on the partner's body.
The Federal Court of Justice has set the standard for the chance of success. There is a duty to reimburse if the probability of a pregnancy is at least 15 percent per attempt (judgment of September 21, 2005, IV ZR 113/04). Private health insurance has no rigid age limits. In practice, the probability of success takes over this role, because it falls with increasing age.
A limit of three attempts does not exist by law either. Limits are set only by the individual plan. Some contracts contain caps on amounts or numbers of attempts, and some entry-level plans exclude fertility treatment completely. Reimbursement therefore depends on the plan, not on the insurer, and this is exactly where the cost question is decided, long before the first appointment at the fertility clinic.