IPA: /ˌpɛrəˈneɪtəli/
KK: /pɛrəˈneɪtəli/
In relation to the period shortly before and after birth.
The baby was monitored closely perinatally to ensure its health.
Perinatally → It is formed from "peri-" (meaning around) and "natus" (meaning born). The word "perinatally" refers to the period around the time of birth.
Think of 'around' ('peri-') the time of 'birth' ('natus') to remember that 'perinatally' relates to the time surrounding birth.