Taken from LaVecchia
"I don't know about other traditions of stregheria, but in the Arician tradition, we're taught that a woman, while menstruating, draws magical energy into herself and then sheds it with her menses. So, it depends on the type of magic being done as to whether she should attempt certain workings or be around others while they do one. Sorta like the certain phases of the Moon can aid or hinder your workings, depending on what they are.
For instance, if she is working a healing magic, she could draw out any "negativity" and then shed or ground it, utilizing the natural process her body is experiencing then. But if she were trying to establish or build up something, that energy would be drawn into her and then grounded. For example, during ritual work, if a woman in the boschetto is menstruating, she waits outside the circle while it is being magically established, so she doesn't draw that energy into herself. Once the circle is cast, she then enters the circle to celebrate the ritual.
So, no, there is nothing "bad" about doing magic whilst menstruating. Some types of workings would be enhanced while others would be hindered or completely negated. You just have to learn how to work with the process."
And followup from Raven:
"According to the Teachings, the blood flow during the time of the "period" absorbs energy and carries it with the blood. On a metaphysical level, menstrual blood is a form of waning energy, as it is derived from the breaking down of material within the female's body. However, it also contains the essence of fertility transformed into the promise of renewal. So, while it would be a good time to do healing work for others (since the blood will absorb energy from the other person and ground it) it would not be a good time to raise energy intended to send to another (unless the blood itself came along with it, attached to a charged object or something of this nature).
We have noted that casting the ritual circle is sluggish if women are bleeding within the circle. We have also noted that the presence of women on their period tends to drain off energy that we are trying to pass to another during a ritual. Again, this is because the women is absorbing or grounding the energy into herself.
However, there are many "positive" uses for menstrual blood in magick. If you have a copy of my book The Wiccan Mysteries, there are some examples on pages 226-228. In this section I talk about blessing the crops with menstrual blood, anointing the dead, and so forth. This addresses the "captured" fertile essence of the blood that flowed from the womb, connecting it with the renewal of transformation."
The moon's phases are typically divided in Stregheria into Dark, Waxing, Full, Waning. Streghe also say the Moon is Dark (no moon showing) for 3 days and Full for 3 days. The Full Moon is of couse when we do lunar ritual, the Veglione. The Waxing Moon is when energies build, the Waning Moon is when energies ebb. Dark is the time of enchantment and possibilities.
Many people assume that there is an "optimal" menstrual cycle for pagans. A menstrual cycle during a Full Moon can feel wrong. But there is no wrong. When you cycle, you cycle. The feeling of "wrongness" comes from the fact that Full Moon the energies associated with a menstruating woman can feel like they are in opposition. A cycle at the Dark Moon is a bit more easy to take. It is a time of mystery and possibility and power. A women bleeding for days and not dying is one of the original human mysteries. A menstrual cycle in the waning phase of the moon will also feel more aligned with the moon's energies.
My menstrual cycle is naturally longer than the 29 day lunar cycle. This means that my natural cycle will shift over the course of the year and occur in anyone of the eternally shifting moon phases. This perhaps is why no matter what magic I feel the need to work, I can always find a way to work *with* whatever the moon's energies are at the time. The only time I tend to avoid working magic are those times when the Moon is "void of course".
There are some that say that standing in the moonlight will adjust a woman's cycle. But no amount of standing in the moonlight has changed this for me. Nor have I seen my cycle change as a result of being around other women. But this may be related to the fact that I have typically worked and lived with other men more than women. And then there is the ability to control our cycles with birth control pills. What I have done is time my birth control pills such that I now have a cycle in the waning of the moon and am completely finished with my cycle by the time the moon is dark. But should I stop taking the birth control pill my cycle will naturally shift into a longer period, closer to 32 days. Then Over time my cycle will again slowly shift so that it swings in and out of phase with the Moon. And I just have to learn how to work with the process.
Some initiate females who have to work solitary have choosen to celebrate on the 3rd day of the Full Moon if they are mensuating at this time. They feel that it better aligns their physical energies with the Moon's (waning) energies.