Monica, We couldn't just leave you sweating on your doctor's uninformed
comments - which you sensibly had already suspected had more to do with his
discomfort levels than any real risk to a foetus.
If he is serious about his concern that breastfeeding will pose a
miscarriage risk, he will also naturally have advised you not to have sex
with your husband. (We have yet to hear of a doctor who has, but are willing
to be surprised!) Orgasm releases much greater amounts of oxytocin than does
breastfeeding. Oxytocin is the hormone responsible for the milk ejection
reflex and for contraction of uterine muscle. As you have noted, women have
breastfed while pregnant for millenia. My feeling is that if a woman
miscarries while breastfeeding, she would have miscarried while not
breastfeeding also!
And just because you can't feel the MER now does not mean that you are not
producing much milk. 2 year olds are very efficient feeders, and in a matter
of 5-10 minutes can easily take a lot of milk. Think about how fast you can
drink a few glasses of water when you are thirsty!

Robyn Noble and Anne Bovey, Brisbane, Australia