We use this part of ICD-10:
Chapter XXI Factors influencing health status and contact with health services(Z00-Z99)
Persons encountering health services in circumstances related to reproduction (Z30-Z39)
Liveborn infants according to place of birth
Z38.0 Singleton, born in hospital
Z38.1 Singleton, born outside hospital
Z38.2 Singleton, unspecified as to place of birth, Liveborn infant NOS
Z38.3 Twin, born in hospital
Z38.4 Twin, born outside hospital
Z38.5 Twin, unspecified as to place of birth
Z38.6 Other multiple, born in hospital
Z38.7 Other multiple, born outside hospital
Z38.8 Other multiple, unspecified as to place of birth
http://apps.who.int/classifications/icd10/browse/2010/en#/Z30-Z39