No prohibition results from suckling, except for what penetrates the intestines from the breast before weaning. [At-Tirmidhi]
"«لا يُحَرِّمُ من الرَّضَاعَةِ إلا ما فَتَقَ الْأَمْعَاءَ في الثَّدْيِ، وكان قَبْلَ الْفِطَامِ». [صحيح.] - [رواه الترمذي.]"