The format varies from area to area, and depends when you were born.
In big cities like Karachi and Lahore, there are are Municipal Birth Certificates that were in English only, but were issued by the UC. Later, there were UC certificates that were Urdu only. Now, most are "NADRA style" (they are not from NADRA, but look like NADRA documents hence why I call them "NADRA style") ones that are English and Urdu.
The key thing to be careful of is that MANY of the "NADRA style" certificates were issued with "late entry" for the registration date. I know of many people who had proper Urdu birth certificates and were told by UC officials that you need to "make new format certificates". They would give the old certificate and be given a new one with a "late entry" date. This caused problems in immigration later. Always keep copies of all documents for this reason.