But it has nothing to do with 40yr olds having babies. They’ve ALWAYS had babies. There’s something ENVIRONMENTAL that causes 40yr old prima para’s to have a higher risk of asd babies and other issues. Something that having babies earlier is protective of.
Yes, it's called age. The older you are at first birth the more likely you are to have complications, pre-natal stress and fetal distress during labor. Not to mention all manner of age related health issues. All of these things are greatly reduced in twenty-somethings.
That something that is protective in having babies earlier is youth and strength. And very likely less stress and worry. While all women worry, I suspect the 40 year old prima para worries more than the 25 year old because she knows the clock is running out.