Why do babies come at different times?

[TheSurgeonsMate]

I may have missed something in the books, but I don't really understand why some babies come "early" and some come "late". Is it because the due date is just an estimate and no-one really knows when you got pregnant, despite which all babies take around the same time to grow? Or, is it because some babies stay inside for longer than other babies? Or, do we not know?

I expect there will be a Nobel prize awarded to the person who eventually works out what makes a baby be born at a specific time. As far as i am aware, nobody really knows yet what sets the chain in motion for labour.

I heard that your gestation cycle is just like your period cycle, it varies from woman to woman. So anything from 38 weeks to 42 weeks is in fact within a "normal" paradigm. In addition it seems to be somewhat hereditary, so if your mother was 40 wks exactly, you are more likely to be.

But the reality is no-one really knows WHY

Also, first babies are 'later' than subsequent babies (as a general trend - it may not play out that way for individual mothers) and different ethnicities tend to have slightly different pregnancy lengths (the same as different ethnicities may have a tendency to be taller or smaller overall).

But as other posters have said no one really knows what triggers labour so until that is found out....

The uterus comes with a major flaw - no calendar. If it did, this whole 37-42 week window could be done away with as babies would know when the date given by the doctors was

Flisspaps

perhaps because they are people and we are all different

in the same way that they sit / crawl / walk / talk at different times, and have different appetities, they choose to leave the womb at different times too?

Thats my theory anyway

In answer to your question, it's both.

Partly it's that most calculations of due dates assume a 28 day cycle.

But mostly it's because they all take slightly different amounts of time to be ready to come out, added to which things like the positioning of the baby seem to affect things being triggered.

Get used to the unpredictability. As Nannyl says, when they come out they are people and you'll spend your life second guessing them!

As others have said no one really knows but I have a theory. I think just as every woman and baby is different it's the same with the placenta - some are more effective than others. In the last few weeks of pregnancy the placenta starts to become less effective but some might start to become so later than others if that makes sense. So if two women are at the same gestation but one has a 'stronger' placenta she might go into labour later than the other.

Phew! If you can understand that I salute you!

So I'm not just ill-informed, it looks like there is a general air of mystery around the question. To be fair, I did suspect that a bit of both might be involved.

I can tell you why my babies came when they did but who knows for other women? It's a peculiar thing between that baby and that woman. We have no control over it.