A couple of things. First, pregnant women are generally excluded from vaccine trials - this isn't something specific to the SARS-CoV-2 vaccines.
Second, what is the scientific basis for thinking that vaccination before pregnancy will affect women at the end of their pregnancy (that is, 9+ months later)? When you propose a possible harm, there should be a scientifically plausible basis for it. Is there one in this case?
> There's a decent bit of data now saying that having been vaccinated in the past increases your chance of infection after 12+ months.
I haven't seen anything to suggest this.
> One problem is that the lives saved and the side effects happen in different and only slightly overlapping populations
CoVID-19 was one of the leading causes of death across a wide range of ages. The idea that only the elderly suffered from it is not true.
> long-term side effects (for both covid and the vaccines) are not yet known or knowable.
Long-term side-effects of vaccination are very much knowable. There is no known mechanism that could lead to these vaccines causing long-term side-effects, and there are very good biological reasons for believing that they do not cause any long-term side-effects. Vaccine side-effects occur within months of vaccination, for reasons that are understood. They do not arise years afterwards (also for reasons that are understood). Saying that there may be side-effects years from now is simply FUD.