Passage of a blood clot larger than a lemon. 

Heavy bleeding: soaks a maxi pad in an hour.

Fever of 100.4 or higher.

Problems with urination:
Burning, or blood in urine, inability to urinate.

Very foul or fish-like odour to vaginal discharge.

Increased pain at site of episiotomy or tear.

Swollen, red, hot, painful area on the leg, especially the calf.

Sore, reddened, hot, painful area on breast, along with
fever or flu-like symptoms.