Hi Ros,

Bergevin Y, Dougherty C, Kramer MS. Do infant formula samples shorten
the duration of breastfeeding. Lancet 1983;May 21;1148-51

Summary: To determine whether advertising by infant formula companies
shortens the duration of breastfeeding, we randomly assigned 448
breastfeeding new mothers to either receive or not receive a formula
sample packet upon discharge from a maternity ward.  These mothers,
unaware of the study, were then telephoned 3 months postpartum by a
research assistant blind to the randomisation status.  "Sample" mothers
were less likely to be still breastfeeding at 1 month (48% vs 84%,
p=0.07) and more likely to have introduced solid foods by 2 months (18%
vs 10%, p=0.01).  These trends became more significant in three
vulnerable subgroups: less educated mothers, primiparas, and mothers who
had been ill postpartum.  Our results suggest that infant formula
samples may shorten the duration of breastfeeding and hasten the age at
which solids are introduced.

Hope this helps.

Jack Newman, MD, FRCPC