It takes about 38 weeks from the time of conception to the day you deliver . This is known  as human conception and is the same for everyone. Very few pregnant women know when they conceived.  Even if you had  intercourse just once during your fertile period , you may not get pregnant right then. The sperms  may be in your tube for a few days before eggs come along for fertilization. This is when the egg is fertilized and conception takes place.

How does anyone know her due

Due date is usually just an estimate. Health care providers  count it using  the first day of your last period. For women with an  average length menstrual cycle , that day is usually about 2 weeks before conception. This is why pregnancy are said to last 40 weeks. However this method doesn’t take into consideration how long your menstrual cycle is or when they might have conceived.

Those who happen to know the exact day they conceived were  perhaps tracking ovulation and know  when the egg must have been fertilized. Your health care provider may revise your due date if she has reason to believe that it is off target.  She will measure your baby during an ultrasound . If your baby is much bigger or smaller that what she should be, the doctor or midwife  will give you a new due date.

However due date is usually an estimate whether its  from a tool , doctor or midwife. Only a small percentage of women  deliver on their due date. You are likely to deliver 2 weeks before or after your due date.