OHSS is divided into the categories mild, moderate, severe, and critical.

In mild forms of OHSS the ovaries are enlarged (5–12 cm) and there may be additional accumulation of ascites with mild abdominal distension, abdominal pain, nausea, and diarrhea. In severe forms of OHSS there may be hemoconcentration, thrombosis, distension, oliguria (decreased urine production), pleural effusion, and respiratory distress. Early OHSS develops before pregnancy testing and late OHSS is seen in early pregnancy.

Criteria for severe OHSS include enlarged ovary, ascites, hematocrit > 45%, WBC > 15,000, oliguria, creatinine 1.0-1.5 mg/dl, creatinine clearance > 50 ml/min, liver dysfunction, and anasarca. Critical OHSS includes enlarged ovary, tense ascites with hydrothorax and pericardial effusion, hematocrit > 55%, WBC > 25,000, oligoanuria, creatinine > 1.6 mg/dl, creatinine clearance < 50 ml/min, renal failure, thromboembolic phenomena, and ARDS.

Symptoms are set into 3 categories: mild, moderate, and severe. Mild symptoms include abdominal bloating and feeling of fullness, nausea, diarrhea, and slight weight gain. Moderate symptoms include excessive weight gain (weight gain of greater than 2 pounds per day), increased abdominal girth, vomiting, diarrhea, darker urine, decreased urine output, excessive thirst, and skin and/or hair feeling dry (in addition to mild symptoms). Severe symptoms are fullness/bloating above the waist, shortness of breath, pleural effusion, urination significantly darker or has ceased, calf and chest pains, marked abdominal bloating or distention, and lower abdominal pains (in addition to mild and moderate symptoms).

Anovulation is when the ovaries do not release an oocyte during a menstrual cycle. Therefore, ovulation does not take place. However, a woman who does not ovulate at each menstrual cycle is not necessarily going through menopause. Chronic anovulation is a common cause of infertility.

In addition to the alteration of menstrual periods and infertility, chronic anovulation can cause or exacerbate other long term problems, such as hyperandrogenism or osteopenia. It plays a central role in the multiple imbalances and dysfunctions of polycystic ovary syndrome.

During the first two years after menarche 50% of the menstrual cycles could be anovulatories.

It is in fact possible to restore ovulation using appropriate medication, and ovulation is successfully restored in approximately 90% of cases. The first step is the diagnosis of anovulation. The identification of anovulation is not easy; contrary to what is commonly believed, women undergoing anovulation still have (more or less) regular periods. In general, patients only notice that there is a problem once they have started trying to conceive.

Temperature charting is a useful way of providing early clues about anovulation, and can help gynaecologists in their diagnosis.

Anovulation is usually associated with specific symptoms. However, it is important to note that they are not necessarily all displayed simultaneously. Amenorrhea (absence of menstruation) occurs in about 20% of women with ovulatory dysfunction. Infrequent and light menstruation occurs in about 40% of women with ovulatory dysfunction. Another potential symptom is irregular menstruation, where five or more menstrual cycles a year are five or more days shorter or longer than the length of the average cycle. Absence of mastodynia (breast pain or tenderness) occurs in about 20% of women with ovulatory problems. Also possible is increased body mass and facial hair, which is relatively easy to treat, and is often associated with PCOS, or polycystic ovary syndrome.

Unexplained infertility is infertility that is idiopathic in the sense that its cause remains unknown even after an infertility work-up, usually including semen analysis in the man and assessment of ovulation and fallopian tubes in the woman.

In the US, up to 25% of infertile couples have unexplained infertility.