Symptoms of ovarian hyperstimulation syndrome often begin within a week after using injectable medications to stimulate ovulation, though sometimes it can take two weeks or longer for symptoms to appear. Symptoms can range from mild to severe and may worsen or improve over time. Mild to moderate OHSS With mild to moderate ovarian hyperstimulation syndrome, symptoms can include: 
Mild to moderate abdominal pain
Abdominal bloating or increased waist size
Nausea
Vomiting
Diarrhea
Tenderness in the area of your ovaries
 Some women who use injectable fertility drugs get a mild form of OHSS. This usually goes away after about a week. But, if pregnancy occurs, symptoms of OHSS may worsen and last several days to weeks. OHSS OHSS Severe OHSS With severe ovarian hyperstimulation syndrome, you might have: 
Rapid weight gain — more than 2.2 pounds (1 kilogram) in 24 hours
Severe abdominal pain
Severe, persistent nausea and vomiting
Blood clots
Decreased urination
Shortness of breath
Tight or enlarged abdomen
