Diane,
A platelet count of 142 is just a little low since the lowest normal is
around 150. I don't know of any links however of low platelet count and
lactation. Surely 90 or 70, as she had previously, is quite abnormal to
me... Normally during pregnancy, it could decrease some 10-20% because
of hemodilution but it usually comes back to pre-pregnancy levels by one
week after delivery.
Anybody has something more on the subject?
Good luck with your counselling!

Louise Dumas, R.N., M.S.N., PhD
Professor-researcher in Nursing Sciences
University of Quebec in Hull