Why does the ob/gyn deliver pregnant woman 40wks after their period instead of 40wks after date of conception?

Question

Why does the ob/gyn deliver pregnant woman 40wks after their period instead of 40wks after date of conception?

Answer 1

Because that is a complete cycle.  period, ovulation, conception pregnancy, even if you new the date of conception, that doesn't include the full cycle.

Answer 2

because no one really knows the exact date of conception so it's easier to go by the date of the last period. I couldn't tell you in the three times I got pregnant what day of the month it was that my husband fertilized my egg.  

Answer 3

They go by LMP in most cases because it is hard to pinpoint ovulation and conception.  Duedates are just an estimate.  They will deliver when you go into labor it isn't just at exactly 40 wks.  Also ultrasounds done early can adjust duedates as well.  40 wks from conception would be 42 wks and at that point there is increased risk of fetal death.  Babies need out by 42 wks or the placenta isn't usually able to keep working properly.  I know my mom had me at 42 wks and I was losing oxygen because the placenta was giving out, I also couldn't adjust my body temp because by that point a baby is just so use to the temp inside the womb.  

Answer 4

Because 40 weeks after conception you would be 2 weeks over due.