Relating to the period from shortly before to shortly after birth, in humans usually from the 20th to the 29th week of gestation to one to four weeks after birth.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 791 (https://doi.org/10.1515/pac-2015-1202)