Looking on the internet deeply has found these results:

twice a month is the most popular phrase on the web.

twice per month 14,130,000 results on the web	twice a month 149,200,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Meetings take place at Saint Peter's Italian Church twice per month on Sundays at 12:30 pm, without no special formalities. Meetings will take place on a first come first served basis. Club Chrome is closed, but the building at 3075 Normandy Road is used for private parties about twice per month, said Neil Patel, the facility's owner. For two years after leaving Good Counsel, mothers meet with their case manager twice per month. Starting dates: For General and indvidual courses students may start every Monday. Beginners and Business/Executive courses starts twice per month, every second week. Live Q & A Calls With Expert (Twice Per Month) Fertilizer: Use at least twice per month. on Saturday afternoon twice per month	Excuse me, but you're 32 years old... you can't appear more than twice a month, and it's exhausting. I'll come twice a month and practice a lot. Found out he had groceries delivered twice a month from the bodega. She only left the apartment twice a month for years. The committee meets twice a month. Went to the movies twice a month. Sofia cannot take a six And twice a month we spend the weekends together.

twice per month

14,130,000 results on the web

twice a month

149,200,000 results on the web

More popular!

Meetings take place at Saint Peter's Italian Church twice per month on Sundays at 12:30 pm, without no special formalities. Meetings will take place on a first come first served basis.
Club Chrome is closed, but the building at 3075 Normandy Road is used for private parties about twice per month, said Neil Patel, the facility's owner.
For two years after leaving Good Counsel, mothers meet with their case manager twice per month.
Starting dates: For General and indvidual courses students may start every Monday. Beginners and Business/Executive courses starts twice per month, every second week.
Live Q & A Calls With Expert (Twice Per Month)
Fertilizer: Use at least twice per month.
on Saturday afternoon twice per month

Excuse me, but you're 32 years old... you can't appear more than twice a month, and it's exhausting.
I'll come twice a month and practice a lot.
Found out he had groceries delivered twice a month from the bodega.
She only left the apartment twice a month for years.
The committee meets twice a month.
Went to the movies twice a month.
Sofia cannot take a six
And twice a month we spend the weekends together.