[1] https://www.sciencedirect.com/science/article/abs/pii/S00029...
[2] https://academic.oup.com/nutritionreviews/article/54/7/203/1...
>The results of this literature review suggest that heavy caffeine use (≥ 300 mg per day) during pregnancy is associated with small reductions in infant birth weight that may be especially detrimental to premature or low-birth-weight infants. Some researchers also document an increased risk of spontaneous abortion associated with caffeine consumption prior to and during pregnancy. However, overwhelming evidence indicates that caffeine is not a human teratogen, and that caffeine appears to have no effect on preterm labor and delivery.
So it's possible caffeine consumption is a sign of a troubled pregnancy rather than a cause of it. I'm sure there's a point where caffeine becomes problematic but that could be said of a lot of things.
There's a paper in NEJM or JAMA that pointed to this as a likely explanation but it's been a few years and don't have time to look for it now. I think they were looking at timing of caffeine consumption and nausea symptoms?
I explicitly said, do your research at the end of the message.
P. S. The book might have been one of the following, I can't remember:
Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong--and What You Really Need to Know (The ParentData Series Book 1) from Emily Oyster
What to expect when you are expecting
I think it's the first one. I read many at the same time, so it's hard to remember which one had the information.