How Occurrence of Pregnancy?

There the couple asked why only 1 time a month but still pregnant aja ... nah loh .... so should know how the hell the occurrence of pregnancy? ---
Pregnancy occurs when sexual intercourse performed when a woman in the time of ovulation or the fertile period (condition in which uterine cells release an egg) and sperm (semen) from male to fertilize the egg from the woman's page.

Fertilized egg will stick to the uterine wall, which will grow and grow for about 40 weeks (280 days).

So even though the couple only have sex once a month but dilakukanya wrote right at the time of ovulation or the fertile women, then the possibility for the occurrence of major pregnancy