I'm not so sure about that. Sperm counts are dropping: https://www.smithsonianmag.com/smart-news/human-sperm-counts...

Maybe we just got better at counting them in the last century and they haven't actually dropped.

I understand the cheekiness of this comment, but reproduction in many societies has indeed become more difficult for many of the same reasons (among several others). The sex hormones that orchestrate lactation and mother-child bonding are largely the same that regulate menstrual cycles, sexual desire, pregnancy, and childbirth. If disruptions to these hormone balances are found to be a major cause in an increase in breastfeeding issues, then this likely correlates strongly with issues effecting the entire reproduction “stack”, if you will.

If you're in your mid-30s or later, reproduction certainly can be tough, even when you're trying.