I went on Google scholar for 30 seconds. The first result was from 2007 for studies from developed countries. It said:
'Results: We screened over 9,000 abstracts. Forty-three primary studies on infant health
outcomes, 43 primary studies on maternal health outcomes, and 29 systematic reviews or meta-
analyses that covered approximately 400 individual studies were included in this review. We
found that a history of breastfeeding was associated with a reduction in the risk of acute otitis
media, non-specific gastroenteritis, severe lower respiratory tract infections, atopic dermatitis,
asthma (young children), obesity, type 1 and 2 diabetes, childhood leukemia, sudden infant death
syndrome (SIDS), and necrotizing enterocolitis. There was no relationship between breastfeeding
in term infants and cognitive performance. The relationship between breastfeeding and
cardiovascular diseases was unclear. Similarly, it was also unclear concerning the relationship
between breastfeeding and infant mortality in developed countries. For maternal outcomes, a
history of lactation was associated with a reduced risk of type 2 diabetes, breast, and ovarian
cancer. Early cessation of breastfeeding or not breastfeeding was associated with an increased
risk of maternal postpartum depression. There was no relationship between a history of lactation
and the risk of osteoporosis. The effect of breastfeeding in mothers on return-to-pre-pregnancy
weight was negligible, and the effect of breastfeeding on postpartum weight loss was unclear. '
ifanz-ibfan.org.nz/documents/health-outcomes-in-developed-countries_Apr'07.pdf
If you have a more recent literature review than this, perhaps you should link to it, because people on MN tend to not respect an argument based on authority - i.e. that you 'work in the field.'