WordNet
safe period
n. that time during a woman's menstrual cycle during which conception is least likely to occur (usually immediately before of after menstruation)
Usage examples of "safe period".
They all went into a duffel bag and remained there for a safe period.
That Cruss may be up to something, but we've interrupted his plans, and this is our safe period.
Twenty-four hours is regarded as a safe period and a plane, as in this instance, can easily make a long-distance flight with them together, at the end of which, of course, they would immediately be stored separately.