Medical Genetics Several medical treatments pose the isk of birth abnormalities. Tetracycline antibiotics affect hard tissue formation bones and teeth. Some anticonvulsant during the foetal period, affecting the lor medicines used for epilepsy may also cause problems. Anyone on long-term medication who is planning to become pregnant, or who has become pregnant, should discuss their situation with their doctorMedical Genetics Several medical treatments pose the risk of birth abnormalities. Tetracycline antibiotics affect hard tissue formation during the foetal period, affecting the long bones and teeth. Some anticonvulsant medicines used for epilepsy may also cause problems. Anyone on long-term medication who is planning to become pregnant, or who has become pregnant, should discuss their situation with their doctor