Like I said, compile a list of different scenarios/options and work out your income and the cost in each case (using a spending diary as Clubman suggested as a basis). This will make for an easier and more concrete comparison.
One other thought would be to try and build up savings in advance of having a second child by setting aside money into a savings account when you get paid (not generally in favour of this as I would agree that saving while carrying debt is less productive but I think it this case it might be useful). This would have the added benefit of reducing your spendable income to a level closer to what you would have to manage on once you are on maternity leave.
One other thought would be to try and build up savings in advance of having a second child by setting aside money into a savings account when you get paid (not generally in favour of this as I would agree that saving while carrying debt is less productive but I think it this case it might be useful). This would have the added benefit of reducing your spendable income to a level closer to what you would have to manage on once you are on maternity leave.