Srimad Bhagavatam Canto 09, Chapter 11, Text 11

SB 9.11.11

antarvatny agate kale
 yamau sa susuve sutau
kuso lava iti khyatau
 tayos cakre kriya munih
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
When the time came, the pregnant mother Sitadevi gave birth to twin sons, later celebrated as Lava and Kusa. The ritualistic ceremonies for their birth were performed by Valmiki Muni.
Srimad Bhagavatam Canto 09, Chapter 11, Text 10
Srimad Bhagavatam Canto 09, Chapter 11, Text 12