Our Sages teach that Mashiach was born (or will be born) on Tisha b’Av.
(Jerusalem Talmud, Berachos 2:4; Eichah Rabbah 1:51)
As a metaphor we can view the Churban
(Destruction of the Temple and other tragic events in Jewish history)
that occurred on this day
as the “birthpangs” of a pregnant woman חבלי משיח preceding birth.
לפום צערא אנרא
According to the intensity of the pain, so is the greatness of the reward,
namely the Ultimate Redemption. In a practical view, because of the Fast, this day is a great stimulus for hastening the birth process and G-d willing there will be born many thousands of “potential” Mashiach candidates this year.
Another possible interpretation of above Midrash is that the Mashiach will be conceived on the Ninth of Av, which is impossible, because of the stringent restrictions on cohabitation, except when it occurs on the Sabbath.
Then we are enjoined to celebrate the day with tremendous joy and simcha, since all signs of mourning are canceled. And since it is such a high period, it is surely an auspicious time for fertility and conception, especially if we can direct our thoughts to elevate the so-called “animal act” into something more sublime and even transcendental. This is what I have tried to convey in the Visual Amulet for Fertility and other works: