What do you think is the greatest invention of all time? Why? Are there any inventions you wish had never been made?
As a 20-year-old engineering student, my reply was "the silicon transistor".
My mother's reply? The birth control pill.
After having two babies, I agree with my mother. In fact I am AMAZED that women have made as much progress as we have considering how recently basic contraceptives have become available.
I love my babies, but each time I had one I really had to take a step back, both the months leading up to childbirth and the months after childbirth were a time filled with travel restrictions, limited hours, smaller scale projects. It affected way more than my 6 weeks of maternity leave. It was a different year. And this different year was even with all the modern conveniences - medical resources to fix anything unusually wrong with me and lower the risk of childbirth complications, a breast pump to take to work.
As an engineer I did this baby thing twice, starting at age 30. In a career that I hope spans decades, two years of baby having isn't a big deal. But it showed me that if we lived in that world my grandma did where women had babies every other year starting from age 20, I would not BE an engineer.
And when you read up on famous women who had big impacts on their world... Harriet Tubman, Jane Austen, Susan B Anthony... it's amazing how many of them were NOT mothers! You either got married and had 10 babies, or you didn't. There was no in between!
So yes, above everything... birth control.