If your savings scheme is locked in until age 50 it is probably a superannuation which will be audited by the government actuary. There are only certain circumstances in which money can be withdrawn from these schemes and evidence needs to be provided. Finance companies need to be strict as if the government actuary identifies that they've been lax about letting people withdraw that don't necessarily fit within the circumstances the finance company will be held accountable.
There may be a clause to transfer to another locked in superannuation scheme but it's not likely that you'd be able to transfer to an unlocked scheme - therefore you wouldn't be able to withdraw the money anyway.
Having a baby is considered normal, like having a mortgage or a credit card, so just having a baby would not make you eligible to withdraw on the grounds of financial hardship. However having a baby (and therefore being on one income) may put you in a position of acute finanacial hardship in which case you would be able to apply to the scheme trustees to allow you to partially or fully withdraw your funds. Generally speaking financial hardship is considered to be when you cannot pay your bills and you struggle afford the simple necessities of life.
If you want more details of the kind of evidence that trustees would consider relevant as proof of financial hardship let me know and I'm happy to post, it's probably best to do it from work where the info is at my fingertips rather than typing it from the top of my head (I've shifted jobs this year and it's been about 6 months since I last reviewed an application for withdrawal on the grounds of financial hardship).
If you do qualify for withdrawal on the grounds of financial hardship you may as well fill in the forms and gather the evidence asap even if you're in one of the frozen schemes. It takes awhile for claims to be assessed so the sooner you get the ball rolling the sooner you can get the money if you're eligible.