In Jain dharma, the key point is:

We should not look only at this one small life (2–4 months or 2–4 years), but at the soul’s very long past.

1. Soul brings old karmas from infinite past lives

• Every jīva has anādi–ananta (beginningless and endless) saṁsār.
• The baby’s soul is not new. It has taken countless births before.
• Whatever violent, deceitful, greedy, angry bhāvs it had in earlier lives have already bound heavy papa karmas.
• Those karmas give fruit at their fixed time, whether the present body is a baby’s body or an adult’s body.

So, even if in this life the child has not yet done much new kashāya, the old, already‑bound karmas can mature and decide the next birth as narak gati.

2. Next gati is mainly decided by:

Traditionally, Jain texts say the next birth (gati) depends on:

1. Previously bound karmas coming into uday (fruition).
2. State of mind (bhāva, leśyā) at the moment of death.

For very short lives (like garbh‑nāś – death in womb, or very early childhood), generally:

• There is very little new karma added in this life.
• So the old karmas from past lives mostly decide the next birth.

If heavy himsā, krodh, māna, māyā, lobha karmas are already waiting to give result as narak, then when the child dies (even in the womb), those karmas can immediately push the soul to hell.

3. “But babies don’t have much kashāya now…”

True in a simple, external sense:

• A small child cannot plan murders, big cheating, etc. like an adult.
• So the visible expression of kashāya is usually less.

But in Jain view:

• Kashāya is a property of the soul, not of age.
• The soul’s inner tendencies (saṁskār, vāsanā) and karmic stock from past lives are already there at birth.
• The present body (small or big) only expresses what is already inside; it does not create the whole character from zero.

So, a baby can be the same soul who was, say, a very cruel person in the immediately previous life. The body looks innocent, but the karma account is not innocent.

4. Going to narak from the womb is possible but rare

• Jain āgamas don’t say that “every baby who dies goes to hell.”
• They only say: if the right type of heavy papa karma comes into fruition at that time, then even a garbha‑jīva can go to narak.
• In most cases, such souls may go to tiryanch, human, or deva gati according to their total karma.

5. Simple way to remember

• Age of body ≠ Age or purity of soul.
• The soul’s next birth is not decided by “How old was the body?” but by:

- What karmas were already bound earlier? - Which karmas came into uday at death? - What was the inner bhāva at that moment?

Therefore, even though very young children seem to have little kashāya now, their long past kashāyas and karmas can still lead them, on death (even from the womb), to narak gati.

You can read more about causes of narak gati here