OK so let's be entirely objective and realistic.
You own your own home and it has enough bedrooms for at least one child?
You can easily afford your rent/mortgage on one income?
Your expenses can easily be met from one income?
(the last two questions in case your baby is ill or you become ill or simply cannot bring yourself to return to work after maternity leave)
Trusting that all is well and you return to work:
You can afford all outgoings including childcare of more than £1k per month?
If things are tight neither of you will mind not having a holiday or managing a week in a Haven caravan?
Both of you are prepared to forego nights out and treats, good clothes, etc.
None of that allows for increased expenses in the context of heating and food shopping let alone clothes as the child gets older. And when the child gets older just think:
Dinner money
Money for school trips (at home and abroad)
Activities such as Tumble Tots/singing/soft play
Music lessons
Drama lessons
Swimming lessons
Dance lesson
Tennis, football, rugby, etc.
Birthday presents, lap tops, phone contracts, driving lessons.
Teenagers eat twice their weight in food every week (my weekly shopping bill is over £200) and then you have the prospect of helping them through uni, etc.
Unfortunately they don't stay little babies happy to wear a hand me down forever and you can't send them up the chimney at 12 to get them to start paying their way.
Sorry if that's brutal OP but if you really think a baby doesn't cost much you might be right but it's a lifetime commitment and they get more and more expensive; especially if you are on the borderline of not being eligible for benefits and not being wealthy.