i personally think you may have trouble getting hospital maternityrecords back to the 60's - they only have to keep them for 25 years after the birth of the last child (although in practice unless they have a rigourous deletion system, you may be lucky)
just apply to the hospital.
Apply to the GP as well - the hospital may have written to the GP to say what happened (if it was something unusual) and GP notes aren't generally destryed till 10 years after the patients death