Baby christenings are formal gatherings generally held in a church and call for attire that is suitable for Sunday services in a house of worship. The clothing a guest wears reflects regard and respect for the occasion.
At Real Simple, etiquette authority Lizzie Post advises that baby christenings are happy events where a child receives his name and is welcomed by baptism into his faith. For women, feminine and cheerful clothing is appropriate, provided it is not low-cut or too clingy. Men's clothing should not be stuffy either, but comfortable and relevant for the occasion. An invitation is generally reserved for family or close friends, so it is acceptable for guests to consult with the baby's parents, especially if the ceremony is at an unfamiliar church.