Reasons not to
Expense: childcare, school uniforms, school lunches, school trips, mobile phones, laptops, university support, bigger car, bigger house, holidays, Christmas.
Stress: GCSEs, A levels, UCAS, degrees. The stress of parenting one teenager was bad enough let alone the thought of going through that 4 times.
Emotional cost: Friendship issues, bullying, relationship issues.
Other: the drudgery of all that cooking, washing and cleaning, years and years of school runs and playdates.
I suspect that the OP doesn’t have older children or teenagers yet. DD wasn’t a horrible teenager, but she had a horrible time at school (bullying and friendship issues), and the emotional toll that something like this takes cannot be underestimated.
What does a fourth child give you that the three you already have don’t?
Reasons to