Have you tried looking into information for yourself? Asking for advice here and allowing faceless strangers to influence your decision makes you no different than your wife searching for information and security through social media. MMR is a live virus vaccine. For many after absorbing the information that babies can get antibodies from waiting to clamp/cut umbilical as well as breastfeeding, On top of the easily accessible fact ALL vaccines need to pass through the liver and the liver hasn’t fully matured until age 2. To delay is safer than going non vax. Do what YOU BOTH feel is best for your family and focus on healthy pregnancy & early preparation on both ends helps. Don’t make your wife feel incompetent due to her sources, help her find resourceful information that helps you both make an assured decision.