The 45-minute operation was carried out after the mother began to suffer contractions.
Ms Douglas, who worked as a carer in an old people's home, went into a coma after being hit by a car near her home in Castle Vale, Birmingham, in December. Doctors discovered she was pregnant only after the accident. The coma began to lift a few weeks ago and she was transferred to a rehabilitation unit at Birmingham on May 21. She was transferred to the maternity hospital on Friday.
Doctors say she is semi-conscious and was told she was expecting a baby. She can recognise familiar voices but can only communicate with facial expressions.
Dr Mike Hocking, a consultant paediatrician, said the baby was 'good-sized'.
'She is being given some oxygen, but we are not worried. It has been a very successful day for Melanie, the baby and the medical team. The baby is not feeding - but she has certainly been crying. She is a bonny baby with brown hair and blue eyes.'
The future of mother and child will be decided by their family, the health authority and social services.