Nearly every metric gets worse

- likelihood to get pregnant

- likelihood to bring child to term

- health risk to mother during pregnancy and child birth

- health risk to baby during pregnancy and child birth

- increased likelihood of multiple birth defects

- increased likelihood of genetic abnormalities

I'm not casting aspersions. My wife and I had kids when she was 38 and 40 respectively. But, the numbers for the risks are stark.

So even if it takes a year instead of one night to get pregnant, which wouldn't really affect long-scale statistics that much, more pregnancies fail, and more people may choose not to try at all because of the risks. That makes sense.

It's got an effect but agreed it's not the biggest effect given what else is going on. I think time might be the bigger factor here when simply discussing biology. If you have kids every ~3 years and don't start until you're 35, you have maybe 1.75 years of kids left in you before it starts getting tenuous. (ie, before the woman is over 40) That same math works out differently if your first kid is at 20.

None of this touches on industrialization and higher education, which seem to be the more universal effects, even if one of their bigger effects is merely to delay motherhood.

That or go "one and done" after having enough fun with:

- Stress on the relationship of trying and failing for a long time - Stress of fertility treatments, if needed - Likelihood of dealing with inevitable miscarriages on the way to a birth - Overall "medicalization" of pregnancy in middle age, and the stress of all that contact with the medical system

Yes it would, because if you don't start until you are 30, you've "lost" a decade of childbearing. That's a pretty serious reduction in the maximum number of children you are likely to produce.

Also if you're 22 and chasing after a toddler, having more kids is going to be much more reasonable-sounding than if you're 32 or 42 doing the same.

Kids is fast.

How many do you want? 2 is quite normal, are you saying you'd only be able to have 3 maximum (but 2 in reality) instead of 12 maximum (but 2 in reality) or what?