Judy,
  I have had strange things happen to my periods with this, my third, child.
With my other two, I didn't menstruate for over 2 years, but this time I had 6
periods in the first 6 months, but never actually ovulated.  I found out I had
postpartum thyroiditis.  I have had Hashimoto's thyroiditis for a few years.
What this all means is that my thyroid hormone level went up after delivery,
then went way down after 3 months then evened out around 6 months.  Once I was
back to my normal low (which I correct with medication) my periods stopped and
haven't resumed in the 6 months since.
  Does she have any other symptoms of thyroid disease?  Weight loss or gain,
not sleeping or being very fatigued?  Might be a good idea to suggest a blood
test.
Lezlie Densmore
LLL of Chicopee/Springfield, MA