* Rh incompatibility: The primary concern is Rh incompatibility. If a woman is Rh negative (Rh-) and the father is Rh positive (Rh+), there's a chance their baby could inherit the Rh+ factor from the father. This can lead to Rh disease, where the mother's antibodies attack the baby's red blood cells. This is more of a risk in subsequent pregnancies.
* Preemptive measures: Knowing the father's Rh factor allows for proactive management. If the father is Rh+, the mother can receive RhoGAM injections during pregnancy to prevent the development of antibodies.
* Planning: Knowing both parents' Rh factors allows for informed family planning.
In short: While not mandatory, testing the father's Rh factor alongside the mother's before conception can be a helpful preventative measure, especially for couples where the woman is Rh negative. The benefits outweigh the minimal inconvenience of the test. A healthcare provider can advise on whether this is necessary based on the individual circumstances.