While the female is lactating (has breast milk) and being in the reverse cowgirl position (Your partner lies on their back; you straddle them, facing their feet) for the best outcome, your partner reaches around to the females titties and squeezes as the breast milk comes shooting out ultimately squirting all over the mating couple.
There is such a rare sexual position that can only be had during pregnancy with a lactating woman.....this beautiful and rare treat is known as the titty milk fountain. Stay shirsty my friends ( in dos equis guy voice)