system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- Why aren’t pregnancies “discovered” earlier on?

I’m not totally sure how to ask this. So most people find out they’re pregnant between 6-8 weeks. And it’s relatively common knowledge that one does not get their period while pregnant. So my question is, how do people not find out they’re pregnant until around 6 weeks if the average menstrual cycle is 4 weeks? Ovulation occurs on, I believe, day 14 in the cycle, so shouldn’t more pregnancies be discovered at 2-3 weeks when the initial next period would occur?

ETA: thank you for the responses! My confusion began with the the whole “you’re 6 weeks pregnant” when it’s more than likely 3-4 weeks of legitimate gestation due to how doctors begin the “clock” at the end of the last menstrual cycle.
gpt
The *average* menstrual cycle is 4 weeks. But:

* Many, if not most, women have some irregularity in their cycles.
* Menstruation can be light and difficult to notice for some women or for some specific rounds of it.
* Some women do not closely track their cycle.
* Cycles can be significantly longer or shorter than the usual 4 weeks.

All of these combine to make a missed period not necessarily immediately obvious.

And finally:

> so shouldn’t more pregnancies be discovered at 2-3 weeks when the initial next period would occur?

The ages given in pregnancies ("gestational age") are from the *last* menstrual period, not from the first missed one. So 2 weeks after conception is, on average, ~6 weeks after the last menstrual period. Counting from conception, the child is about two weeks younger than this number.