This might not even be about the vaxx. It might just be another outright lie to scare women away from having children. It is known that pregnancy does carry an increased risk for heart attack and stroke at any age (the extra load on the mother's system from the baby is inevitable). However, the risk is minimal for healthy women and since continuing your blood line is considered a worthy endeavour by sane people, it is worth the risk. Pregnancy has been a risk for women since humanity has existed. Due to some positive medical advances, right now it is actually the least risky time in history for a woman to be pregnant.

I'm also thinking, are they trying to imply that women should wait into their 30s or 40s to get pregnant or are they saying they should aim to get pregnant before their 20s? I would agree that trying to get pregnant at 40 is less risky in terms of pregnancy side-effects than at 20 because with the likely outcome at 40 being no pregnancy, that also means no pregnancy risk. It unfortunately also comes with the side-effect of no children.