Vaccines are very well understood, the reason for those exceptions is the very high complexity and sensitivity of pregnancies, there’s no significant indicators of danger but they aren’t willing to risk missing some unknown.

women are enrolled in vaccine safety studies, sometimes those women will inadvertently become pregnant, and there’s an opportunity to ethically study what happens to those women.”

This is the point of the study, the point of the article, the interest being advocated here by Dr Rachael Purcell. Conducting vaccine trials on pregnant women.

This is essentially the exact opposite of what you’re saying. This is just collecting data on a group of women who only incidentally end up fitting the criteria. Nobody’s selecting pregnant women to expose them to anything.

As the vast majority of the population are not pregnant women

…there is no reason to try to change whatever bad is expected to happen to them. I can understand your point, but it doesn’t sound humane to me