These  amalgam fillings are harmless once done. If you are planning a baby. Visit a dentist for a check up. Just like you visit a gynaecologist. Treat any dental  issues if present now. Dental amalgam fillings once in place don't cause any issue for the mother or the fetus.

Do not worry too much mam, half of world used amalgam fillings since last 4 to 5 decades... Composites are sure replacement options and are really good as they are cured and bonded to tooth surface... actual amount of mercury which will leak from old filling is really very less and may or may have further damages what you are thinking off... Better get them changed asap. To understand better visit - https://www.ar32.in/Dental-Treatments/tooth-restoration.html

If the mother has mercury fillings in her teeth the fetus will not only be exposed to mercury released from its mother’s fillings at the moment of conception. But throughout the entire gestation period. This means that the fetus is being exposed to poisonous elemental mercury from dental fillings before it even has a tooth. The mercury vapor released from silver fillings is more toxic to the fetus and nursing baby. Mercury is known to cause birth defects and learning and developmental disorders. Mercury the most coming and known disorders are : autism, attention deficit disorder. We encourage every woman of childbearing age to have these toxic fillings safely removed prior to becoming pregnant in order to save new generations and your own kids from the cause of birth defects and learning and developmental disorders

It’s better to change the filling and go for composite ( Laser filling) its better option Do consult here for the needful

Hello Don’t worry mam,this is common restoration in india