Does anyone know what are the side effects of a baby born in the breech position?

It depends. If your breech baby is delivered by cesarean section , there is probably no significant issues. Sometimes the baby will have been in that position for a considerable time and may have early issues with hips, but not usually. The increased risk comes from vaginal birth, since the last part to deliver is the head. And with twins delivered vaginally, the second twin is often delivered as a breech.
Breech position. About 5% of babies present at the time of delivery as a breech. Most singleton breech babies will be born by cesarean section which reduces the risk of delivery complications. A breech baby may persistantly keep their feet up near their head, but this is only due to in utero positioning and will go away.