- twin pregnancies with both fetuses alive between 18 and 34 weeks of gestational age and followed at our twin clinic; absence of absolute contraindications for breastfeeding, such as positive serology for HIV, HTLV; absence of use of lactation inhibitors to treat prolactinoma, such as cabergoline and bromocriptine; and absence of major malformation of one or both twins that could preclude breastfeeding, including gastrointestinal defects, cleft lip and cleft palate, or malformations that would require neonatal surgery with prolonged hospital stay.