If you know your ovulation date,?

Question

how can you determine your due date?

And is this more accurate than a first trimester ultrasound?

And can you still go over 2 weeks and be considered normal?

Answer 1

The docs/midwives use FDP + 9 months + 1 week. This assumes that ovulation is on day 14. You can make up a false FDP if your ovulation date is a bit off from day 14: just subtract 14 days from your date of ovulation, and tell the doc/midwife you want to use that date because you know you ovulate differently than their pregnancy wheel calculates.

Babies tend to grow at different rates, so ultrasounds are probably more accurate. But really, there isn't any way to be completely accurate. What's important is that they don't force you to have the baby earlier than full-term. Generally, two weeks under to two weeks over is full-term.

Answer 2

The doctor uses "last period" because its more definite. If your periods were normal, this would be 2 weeks before ovulation.
The usual method is to use the "normal" development and timing - 280 days (or about 268 since conception - 274 for the first baby, some say). Working with weeks and 4-week "months" makes calculations much simpler than trying to figure in calendar months of different lengths. If you're really concerned, find the calendar on the web.
The ultrasound is based on how the baby develops. It can tell you whether things are on schedule based on which bits are how developed, but it's not going to nail down a day - but probably no worse than a week or so early on.
Doctors worry about babies going over 2 weeks because the risk of complications go way up. I have heard of perfectly normal 10-monthers, but generally some problems start to occur and doctors don't let it happen, since they can easily induce labour.

Answer 3

you count 40 weeks from the first day of your last period....for most women that would about 38 weeks from your ovulation date.....no real clue which is more accurate....but i think that the ultra sound is very accurate