Bimestrial - frequency of use or alternatives

I would like advice on the word bimestrial.

Here on Brazil its equivalent is commonly used, but I've noticed it might not be so used in English. But what would be the alternatives?

For example, in this sentence:

"The course modules are distributed throughout two years in bimestrial (two months) periods, as shown in the following chart:"

Is it so sparingly used by natives that would require that I put under parenthesis its meaning, as precaution?

Bimestrial , for some reason, didn’t gain currency in the English language as it did in other European languages. Bimonthly, on the other hand, has its drawbacks:

bimonthly

1) Occurring once every two months; bimestrial

2) Twice every month; semimonthly.

Usage:

Because of the ambiguity of this word, it is best to avoid it. Instead, use twice a month or every two months as appropriate.

(Wiktionary)

Google Books usage frequency for: bimestrial, bimonthly, every two months, twice a month.