fertile phase vs fertile period

fertile phase and fertile period both are nouns.

Word	Noun	Adjective	Verb	Adverb
fertile phase	Yes	No	No	No
fertile period	Yes	No	No	No

As nouns, fertile phase and fertile period are synonyms defined as:

fertile phase and fertile period: the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)

fertile phase (noun)	fertile period (noun)
the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)	the time in the menstrual cycle when fertilization is most likely to be possible (7 days before to 7 days after ovulation)