14 weeks pregnant, need chest X-ray for visa to give birth. Would the risk be lower if I delay until 20 weeks gestation or the same if I have now?

Later = better, but. Fortunately a single chest xray exposes only a very small amount of radiation. Radiation exposure during early pregnancy incurs higher risk because of organ formation/development. 14 vs 20 wks probably does not make much of a difference here. Also, you are likely to be provided a lead-shield over the lower abdomen/uterus to reducethis small radiation exposure to baby. Congtrats and good luck.