OBJECTIVES: The purpose of this study was to examine the potential impact of 
severe Ovarian hyper stimulation syndrome (OHSS) on the risk of preterm birth. 
Severe ovarian hyperstimulation syndrome is a serious complication in the 
methods of in vitro fertilization. The pathophysiology of this process is not 
clear enough and the treatment is symptomatic. Human chorionic gonadotropin 
(h-CG) is the most important known cause of this condition. Findings of other 
authors often do not match when it comes to complications that may occur in 
pregnancy.
METHODS: In the Gynecology and Obstetrics Clinic "Narodni Front" a case control 
study was conducted on 50 female patients with severe forms of OHSS in the 
period from January 2008 to March 2015. A control group was created based on age 
and it involved 59 patients with pregnancy achieved with IVF/ICSI during the 
same period, but in which OHSS did not occur.
RESULTS: Patients with the pregnancy complicated by OHSS, had a considerably 
higher rate of preterm labor, whether this was labor before gestation week 37 
(56.0% vs. 30.5%) or before gestation week 34 (34.0% vs. 6.8%); significantly 
lower weight of newborns, as in the newborns with low body weight <2500g (45.6% 
vs. 25.0%) and specially in the newborn with very low body weight <1500 grams 
(19.1% vs. 3.8%), as well as preterm premature rupture of membranes (PPROM), 
(11.76% vs. 1.59%).
CONCLUSIONS: Pregnancy achieved by the IVF/ICSI method in which severe form of 
OHSS has been developed could have an increased risk of preterm birth.