<prompt> Perinatal period is defined as -From 20 week of gestation to bihFrom 28 week of gestation to bihFrom 28 week of gestation to one week after bihFrom bih to one month after bih  <response>: Perinatal period is defined as from 28 week of gestation to one week after bih. REF. PARKS TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 519 