Parents with normal chromosomes and abnormal fetal chromosomes cannot be sure whether fetal chromosomal abnormalities will occur next time because there are many causes of chromosomal abnormalities. Parents have normal chromosomes, which means there is no genetic factors causing fetal chromosome abnormality, but factors such as the environment, medications, and diseases can affect the chromosomes of the fetus. Excessive exposure to chemicals such as lead during pregnancy can cause chromosomal abnormalities in the embryo. When a pregnant woman has been infected with cytomegalovirus in the early stages of pregnancy, it may also lead to chromosomal abnormalities in the fetus. Erythromycin may also cause chromosomal abnormalities in the fetus if the man has been taking it orally for a long time. If you want to reduce the probability of chromosomal abnormality in your next child, you should avoid these factors that lead to chromosomal abnormality in the fetus, and also check the chromosomes of the fetus.