If a person accidentally took 2 ampicillin antibiotics within 1 hour, is it a cause of concern?

Is it considered an overdose? I accidentally took an ampicillin 500 mg capsule after taking one an hour earlier (I meant to take different kind of pill from a different prescription and got mixed up). The prescription says to take it 4 times a day, usually every 6 hours. Should I be worried if I accidentally took 2 one hour apart? I'm also 7 months pregnant and concerned if this has any effect.