You think our government respects people taking time to rear offspring? Of course not! They're not contributing their labour to our economy while being parents so we've structured the incentives to start families in such a way that they're driven back to work ASAP. Strictly speaking: having children is bad for our labour force and should be avoided.
In terms of across the board consumption, there is nothing as productive as a modern child. Clothes, consumable goods, travel sports, recreations, hobbies, and diversions all lead straight to the consumption that is so vital to our economy.
And yet, with sicknesses, evening activities, and other problems, there is nothing that disrupts an individual worker's productivity as a child.
I'm not sure I am smart enough to come up with an equation, but, it's in there somewhere to tell us whether a child is a net positive or negative influence on our Economy than the other.
I have two kids and it isn't that bad at all. Very small loss of productivity for me except when I took parental leave for 3 months. I have grandparents that live nearby and they can help with sickness and other babysitting though.
Just so happened that my family had to move for work, health, etc. I love raising my kids so it’s fine. It has been the equivalent of drop kicking my career against a brick wall occasionally, if I’m being honest.
The best economics can only tell you how to convert value into different units. It can't tell you what value is.