No, they are not the same.

• Garbha Kalyanak means the auspicious event when the Tirthankar’s soul enters the mother’s womb.
• 14 dreams are the auspicious dreams seen by the mother before the birth of a Tirthankar, which indicate that a महान आत्मा is coming.

So:

• 14 dreams = sign / indication
• Garbha Kalyanak = actual auspicious event of conception

In Jain tradition, both are connected with the life of a Tirthankar, but they are different events.