According to Hindu scripture, human life begins when the male semenfertilizes the female egg.
karmana daiva-netrena jantur dehopapattaye striyah pravista udaram pumsoretah-kanasrayah (SB. 3.31.1)So there is no debate within Hinduism as to when life begins. Thusabortion involves killing, which in most cases is not acceptable. AlthoughI have not studied the argument, it is likely that on similar groundsHinduism would oppose stem cell research, which as I understand it is mosteffectively done on the stem cells of aborted fetuses.
"By divine arrangement in accordance with the principle of karma, theliving entity enters into the womb of a woman through the particle of malesemen to assume a particular type of body."
Oftentimes the women in my family are not allowed to go to the temple,practice pujas, or even go into the kitchen when they have their menstrualperiod. When I was in India, my aunt said she was "cursed" because shealways got her period during important festivals, and could notparticipate in the ceremonies. Although it may have been hygienic in theolden days, now it seems pretty useless--after all, there are clean andsanitary ways to handle the situation. I would like to know where itstates (in Hinduism) that women are not allowed to do anything duringtheir period? And why do we continue to practice this seclusion even inthese days; after all, isn't the menstrual cycle (which allows a woman toprocreate) one of the most natural and important of bodily functions?
Prohibitions regarding women's involvement in ritualistic worshipduring their menstrual cycle are implied throughout the scripture. Atleast this is how those who have formed lineages have interpreted sectionsof the scripture that discuss this period. The Bhagavata Purana forexample attributes the menstrual cycle to one fourth the karmic reactionto Indra's inadvertent killing of a brahmana. According to that Purana,Indra killed a brahmana and was then chased by the karmic reaction to thiskilling. He then negotiated with four groups who each agreed to absorb onequarter of the reaction in exchange for a blessing. Women got the blessingthat they could have sex during pregnancy without endangering the embryoin exchange for accepting the monthly menstrual cycle.
sasvat-kama-varenamhas turiyah jagrhuh striyahIt is also stated in this Purana that one should not eat food seen by awoman during her monthly period, bhunjitodakyaya drstam (BP. 6.18.49). Youmay also find something about this in Manu Samhita.
rajo-rupena tasv amho masi masi pradrsyate (BP. 6.6.9)
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The latter seems more likely, and one merely needs to read up on thevaried fears premodern cultures had about this period in a woman's life toknow that their understanding involved considerable superstition. Hinduculture is no exception. Indeed, even the most orthodox Hindus havealtered their position on this issue in today's world, while for the mostpart holding on to some part of premodern thinking about it with regard toritual purity. Thus while Hindu women are no longer confined to solitude,and the clothes worn during their monthly cycle are no longer burned, theyare often prohibited from ritual worship and even entering the temple. Inmy opinion, it is likely that these current prohibitions will also belifted in time. The main concern in Hinduism seems to be with regard tobleeding, as even men who are bleeding from any particular ailment are notallowed to participate in ritualistic worship. However, today the questionremains as to whether modern methods of cleanliness that control bleedingdo not change the equation.
In my particular lineage, there is already a difference ofopinion. Visvanatha Cakravarti Thakura states in his Bhagavad-gitacommentary on Bg. 9.26 that the word prayatatmanah refers to physicalpurity and thus prohibits women from engaging in temple worship duringtheir menstrual period. But my own guru considered that such worship didnot contradict the guidelines outlined by the lineage's founders. In thisregard he wrote, "According to the smarta viddhi, women cannot touch theDeity during their menstrual period, but the goswami viddhi allows. But itis better not to do it. One thing is that the seva can never be stoppedfor any reason. This also for the cooking." (Here Prabhupada implies that women can do these services for the Deityduring their menstrual cycle if necessary.)
In the bhakti tradition, God is more accessible, especiallyKrsna. However, overall in this age (Kali-yuga) the most effectivespiritual practice is chanting God's names, and there are no prohibitionsfor Krsna kirtana. Such chanting can be performed by anyone at any timeunder any circumstance.