Hello, I went through your query, it is not hormonal injection. Rhesus disease can largely be prevented by having an injection of a medication called anti-Dimmunoglobulin. This can help to avoid a process known as sensitisation, which is when a woman with RhD negative blood is exposed to RhD positive blood and develops an immune response to it. Since your first baby is O negative,, she can take this injection, since she as not sensitized yet, which helps to prevent rhesus disease of babies in subsequent pregnant. Talk to your gynecologist to know more.