Females having the normal menstrual cycle of 28 days, will be able to conceive in between Day 10-Day 15 from the first day of her periods. 

The concept of IVF:

In Vitro Fertilisation means "Fertilisation in- glass" that is fertilization outside the human body. It was initially developed for fertility in females who had blocked or unfunctional fallopian tubes. At present IVF is recommended for patients who are unable to conceive due to several other causes also.