Risk of birth defects using antibiotics in pregnancy

We have just discovered that my wife is 4 weeks pregnant (fertilization took place between 15 to 20 days ago). My wife has been having unusual periods recently where a week before menstruation she has been seeing small traces of blood. So when a few days ago, she saw the small traces of blood again, we assumed she was not pregnant. My wife then took 3 doses of sparfloxacin (0.2g/dose) over a day and a half as this had been prescribed by a doctor to get her periods in order. After taking the three doses, my wife realized that her period was perhaps not coming and was maybe pregnant. We have since been to see three doctors about this and they have all told us that if my wife took this medicine within 14 days of the fertilization process then there should be no need for concern. However, if this was over 14 days (as it seems to be), then there is a very strong chance that there will be serious birth defects to our little baby (one doctor put the risk at 10-30%). All three doctors recommend that we should abort this baby and try again in 6 months. My wife and myself are utterly devastated and cannot believe that we have made such a stupid mistake. We have searched for lots of information and found that between 3 weeks and 8 weeks, the fetus is indeed very fragile to certain drugs. We have found one article that suggests that the US FDA apparently classifies Sparfloxacin as category X during the 1st trimester and then as category C during the 2nd and 3rd trimester. All other information that we have found just suggests that the effects are unknown. Is this information correct? What should we be considering?