Eggs do not grow, they are produced by other animals. Such as chickens.
Its a symptom of any number of things; Pericardial Tamponades (fluid buildup of sac surrounding heart), a heart contusion, a dysrhytmia like Ventricular Fibrillation or Ventricular Tachycardia...
Most of the time, coins pass through children's bodies and cause no harm. So, if a child doesn't choke or do anything alarming after swallowing a coin, most of the time it means they're okay. Knowing what fertility is tho, the coin is definitely not causing it. Coins aren't too thick and they'd decompose cuz of the acid in less than 10 years.
*I REALLY hope this is just a random question and isn't really happening right now in your life. God Bless :)
