Ovarian hyperstimulation syndrome ups risk of pregnancy complications

Women with ovarian hyperstimulation syndrome (OHSS) are at higher risk of experiencing postpartum haemorrhage, large birthweight, neonatal respiratory distress syndrome, and intraventricular haemorrhage, suggests a study presented at ESHRE 2024.

“OHSS is an iatrogenic condition caused by ovulation induction,” said lead author Dr Jeong Hwan Shin, Obstetrics and Gynecology, Korea University Medical College, Seoul, South Korea.

An exaggerated response to excess hormone, OHSS may occur in women who take fertility or injectable hormone medications. Although most cases are mild, severe ones are potentially fatal and require hospitalization. [https://www.mayoclinic.org/diseases-conditions/ovarian-hyperstimulation-syndrome-ohss/symptoms-causes/syc-20354697]

Mothers with OHSS in this study tended to be younger and had a greater incidence of primiparity and caesarean section. In addition, they were more likely to have a diagnosis of prepregnancy hypertension or diabetes mellitus and gestational hypertension or gestational diabetes. [ESHRE 2024, abstract P-754]

Women with mild-to-moderate OHSS had a 38.2-higher risk of postpartum haemorrhage than those without OHSS (adjusted odds ratio [aOR], 1.382, 95 percent confidence interval [CI], 1.223‒1.562).

Average birthweight of newborns did not differ between participants with and without OHSS. However, mothers with severe OHSS had a 62.4-percent higher risk of macrosomia than those without OHSS (aOR, 1.624, 95 percent CI, 1.168‒2.259).

Additionally, the risk of respiratory distress syndrome was increased by 36.8 percent in women with mild-to-moderate OHSS relative to those without (aOR, 1.368, 95 percent CI, 1.149‒1.629). The mild-to-moderate OHSS group was also at greater risk of developing intraventricular haemorrhage than the non-OHSS group (aOR, 2.697, 95 percent CI, 1.338‒5.437).

“Although OHSS occurs during early pregnancy, further research is required to determine its long-term effects,” Shin said. “Especially, if the incidence of intraventricular haemorrhage is significantly higher in the OHSS group, particularly among uncommon full-term neonates, further studies are warranted.”

Korean database

In this retrospective study, Shin and colleagues used a combined dataset from two primary sources, namely the Korea National Health Insurance (KNHI) claims database and the National Health Screening Program for Infants and Children (NHSP-IC) database.

They then identified women who gave birth between 1 January 2012 and 31 December 2020 from the KNHI claims database. Those with multiple pregnancy or had missing data were excluded. Pregnancy outcomes, such as preterm birth and postpartum haemorrhage, were identified from both KNHI and NHSP-IC databases.

Eligible women were grouped according to the presence or absence of OHSS and hospitalization within 3 months prior to conception: mild-to-moderate OHSS group (n=2,293), severe OHSS group (n=606), and non-OHSS group (n=2,562,562).

This study was limited by the lack of data on the controlled ovarian stimulation protocol, type and dose of gonadotrophin used, hormone concentration, and embryo transfer method employed. In addition, hospitalized patients were categorized as having severe OHSS despite potential variations in the causes of their hospitalization.