The most successful women I know in science either never had kids or had them very young and started their career afterwards.
Some of us also have spouses willing to do a large amount of childcare. I had my daughter just before earning tenure in a scientific field and my husband has taken a huge amount of the childcare responsibilities. Considering he is in the same field and did not yet have tenure, that was a major decision.
Some men are willing to provide that sort of support and it shouldn't be forgotten.
