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Everyone knows that pregnancy lasts nine months, right? Well, not exactly. The medical profession actually measures the length of pregnancy in weeks, not months, and it turns out that the average length of pregnancy (or gestation) for humans is 40 weeks, which is actually closer to 10 months. We divide the gestation into thirds to determine the trimester, so that the first trimester is from weeks zero Through to 13, the second trimester from weeks 13 through to 28, and the third, or last trimester, is from 28 weeks until delivery. While the average gestation is 40 weeks, you may deliver before or after 40 weeks. Delivery any time prior to 37 weeks gestation is considered pre-term, delivery between 37 and 42 weeks is considered term, and delivery after 42 weeks is considered post-term.
40 weeks from 1st day of the last period
Gestatinonal age / initial development | Gestational age by weeks | Gestational age by month |
1st day of last period is calculated by doctors as 1st day of conception | Calculated 1st day | ——- |
Day of ovum ( egg ) fertilization is actualy the 1st day of conception | by end of 2nd week of period day 14th from 1st day of mensess | 0 |
Period will be messed and pregnancy test will be +ve after 2days | end of 4th week ( day 28 from 1st day of last period) | 1/2 |
Intrnal organ of fetuos is completed , fetal heart pulsation is seen | End of 8th week | 1 1/2 |
Placent fuction is takenover and 1st trimester of pregnancy is completed | End of 12th week | 2 1/2 |
Baby movement may be felt | 16-18 week | 3-4 1/2 |
Med of the jorny ( med of pregnancy ) | End of 20th week | 4 1/2 |
At this stage fetous conseder as baby, If delivery occurred before this date it consedered as abortion if delivery occurred after this time it will be consered as a baby and life support is provided | End of 24th week | 5 1/2 |
2nd trimester of pregnancy is completed | End of 28th week | 6 1/2 |
Bigining of last month of pregnancy | End of 36th week | 8 1/2 |
If delivery occurred befor this date baby consedered preterm If delivery occurred after this date baby id fully mature | End of 37th week | 8 3/4 |
end of conception or pregnancy | End of 40th week | 9 1/2 |
1week over due date , thinking of induction of labbour start | End of 41st week | |
Not recommended to wait any more , risk on baby is high | End of 42nd week |
We do recommend to calculate in weeks , more clear.
OBGYN Consultant
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