
==== Front
CMAJ
CMAJ
9711805
CMAJ : Canadian Medical Association Journal
0820-3946
1488-2329
CMA Impact Inc.

10.1503/cmaj.240213
196e1012
Practice
Five Things to Know about …
Ovarian hyperstimulation syndrome
Rosenberg Hans MD
Rangwala Sohil MD
Magee Bryden MD
Departments of Emergency Medicine (Rosenberg), Family Medicine (Rangwala), and Obstetrics and Gynecology (Magee), University of Ottawa, Ottawa, Ont.
Correspondence to: Hans Rosenberg, hrosenberg@toh.ca
9 9 2024
09 9 2024
196 29 E1012E1012
© 2024 CMA Impact Inc. or its licensors
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY-NC-ND 4.0) licence, which permits use, distribution and reproduction in any medium, provided that the original publication is properly cited, the use is noncommercial (i.e., research or educational use), and no modifications or adaptations are made. See: https://creativecommons.org/licenses/by-nc-nd/4.0/
==== Body
pmcOvarian hyperstimulation syndrome occurs almost exclusively after ovarian stimulation during in vitro fertilization (IVF)

Hyperstimulation of the ovaries can trigger the release of vasoactive peptides causing vascular permeability, which leads to hypovolemia, ascites, and pleural effusions. The resulting hemoconcentration increases the risk of venous thromboembolism and end-organ injury.1

Mild ovarian hyperstimulation syndrome affects 20%–33% of IVF cycles, but severe cases are rare (< 1%)2

More than 20 000 IVF cycles are performed annually in Canada.3 Most fertility clinics will manage mild and moderate cases outside of the hospital. Risk factors for severe ovarian hyperstimulation syndrome include age younger than 30 years, polycystic ovary syndrome, large number of eggs retrieved (> 20), and IVF followed by fresh embryo transfer that leads to pregnancy.4

Ovarian hyperstimulation syndrome can present early (< 1 wk) or late ( ≥ 1–2 wk) after egg retrieval

Patients most commonly present with abdominal pain and distension. Additional symptoms include nausea and vomiting, shortness of breath, and reduced urine output.1 More severe cases may involve electrolyte disturbances, pleural effusion, or venous thromboembolism. The presence of fever or peritonitis expands the differential diagnosis to include ovarian hemorrhage or torsion, pelvic infection, and bowel perforation.

Investigations should include bloodwork and ultrasonography

Transabdominal and transvaginal ultrasonography allows for ovarian volume assessment and quantification of ascites.4 Laboratory investigations should be used to quantify serum human chorionic gonadotropin for appropriate clinical interpretation and identify elevated hematocrit, leukocytosis, electrolyte abnormalities, hypoproteinuria, or decreased renal function.

Management of severe ovarian hyperstimulation syndrome is supportive and usually includes volume resuscitation, paracentesis, and thromboprophylaxis

Early involvement of a reproductive endocrinologist and infertility specialist in suspected cases is vital. Crystalloid fluids and paracentesis are first-line supportive therapies for reversing hemoconcentration and reducing ascites, respectively. Prophylactic low-molecular-weight heparin should be started early, given the hypercoagulable state of affected patients.5

Competing interests: Hans Rosenberg reports payment for expert testimony from the Canadian Medical Protective Association and travel support from Canadian Women in Medicine. Bryden Magee reports payment from BioSyent as an advisory board member. No other competing interests were declared.

This article has been peer reviewed.
==== Refs
References

1 Timmons D Montrief T Koyfman A . Ovarian hyperstimulation syndrome: a review for emergency clinicians. Am J Emerg Med 2019;37 :1577–84.31097257
2 Shmorgun D Claman P . No. 268: The diagnosis and management of ovarian hyperstimulation syndrome. J Obstet Gynaecol Can 2017;39 :e479–86.29080733
3 Canadian Assisted Reproductive Technologies Register Plus (CARTR Plus). Canadian Fertility and Andrology Society. Toronto, Ontario, 65th Annual Meeting; 2023 Sept. 20–23.
4 Practice Committee of the American Society for Reproductive Medicine; Practice Committee of the American Society for Reproductive Medicine. Prevention and treatment of moderate and severe ovarian hyperstimulation syndrome: a guideline. Fertil Steril 2016;106 :1634–47.27678032
5 Petrenko AP Castelo-Branco C Marshalov DV . Assessing the usefulness of severity markers in women with ovarian hyperstimulation syndrome. Reprod Sci 2021;28 :1041–8.33063288
