Constance Fisher -- Fairfield, Maine, 1954, 1967 

Fisher was twice committed to the Augusta State Hospital after 
separate incidents in which her husband arrived home from work 
to find the couple's children dead. In 1954, Fisher drowned her 
first three children in the bathtub. After five years at the 
hospital, Fisher was declared cured and returned home. In 1967, 
she drowned three more of her children. Found innocent as a 
result of mental illness, Fisher was recommitted. In October 
1973, duck hunters came across Fisher's drowned body about 
seven miles downriver from the hospital. 

http://www.chron.com/cs/CDA/story.hts/special/drownings/957431