"Category = short acting benzodiazepine sedative, hypnotic.
In one study of 22 women 15 mg midazolam given orally
each evening produced no detectable level of midozolam
seven hours after dose, even 5 days postpartum. Midazolam
disappears rapidly from milk with undetectable levels after 4
hours. Waiting 4 hours after dose would expose the infant to
minimal midazolam.
AHL=1.2 - 12.3 hrs.
PHL = 6.5 - 23 hrs.
M/P=0.15
PK = 2-5 min.(IV)
PB=97%  "

from Medications and Mother's Milk, 4th ed.
Thomas W. Hale, R.Ph., Ph.D
Available from Pharmasoft Medical Publishing, 4606 Oregon,
Amarillo, TX 79109

Hope this helps.

Margery Wilson, IBCLC
Massachusetts Institute of Technology