What Causes Delayed Periods After Taking Contraceptive Pill?

hi my name is Rajiv Agrwal . I normally use condoms for a safer sex. but that day i did sex with my wife using today contraceptive pill. i did that 18 days back( at 10th march). her date ended up at 22nd of feb. her date normally shift 5-6 days backward . so today she should have date. But she get a very small amount of blooding yesterday ,but it stop. she did not bleeding a drop form last 24 hours. my problem is if i go ahead and plan the baby thn ..i used today pill during that intercourse, and i have doubt the baby will not be good in health if we plan for it. we are also thinking for delay this baby. my heart says she has got pregnant. plese suggest me some thing in this situation. how to terminate this 16 day pregnancy easly.