Preterm delivery risk factors in singletons born after in vitro fertilization procedures.

OBJECTIVES: Women delivering singletons after in vitro fertilization (IVF) procedures have a greater risk of preterm delivery (PD). The aim of our study was to analyze PD risk factors and to identify those that could possibly be prevented. STUDY DESIGN: In our matched controlled study we analyzed 1127 singleton deliveries after IVF and transfer of fresh embryos performed at the University Medical Center Ljubljana between 1 January 2002 and 31 December 2010. For every delivery included in the study group we chose three consecutive controls matched by maternal age, parity and maternity hospital. The main outcome measure was PD (<37 weeks). Investigated variables were: previous PD (PPD), conization, pregestational diabetes mellitus, uterine anomaly, operation on the uterus, chronic renal disease, maternal age and parity, and body mass index (BMI). Variables investigated within the IVF group were: stimulation protocol, laboratory procedure, number of retrieved oocytes and number and quality of transferred embryos. RESULTS: The PD rate after IVF was 1.5 times higher than after natural conception (11.5% in the IVF group and 7.7% in the control group, p<0.001). Conization and chronic renal disease were shown to be significant risk factors for PD in both the IVF group and the naturally conceiving controls. BMI>30 was an important risk factor only in the IVF group (OR 1.86 (1.06-3.27) vs. 1.10 (0.67-1.80)) and PPD only in the controls (OR 1.83 (0.78-4.28) vs. 3.22 (1.55-6.67)). Among the investigated PD risk factors, an IVF procedure was shown to be the fifth most important one. On analyzing parameters of the ovarian stimulation and IVF procedure, no PD risk factor was identified. CONCLUSIONS: IVF was shown to be a significant risk factor for PD. In the IVF population, BMI plays a far more important role in PD than in the fertile population. In our research PD reoccurrence in IVF group was less than expected, which could perhaps be explained by the surgical correction of gynecological pathology and, where necessary, its being combined with cerclage. The investigation of parameters related to the IVF procedure did not identify any risk factors for PD.

Singleton pregnancy outcomes after in vitro fertilization with fresh or frozen-thawed embryo transfer and incidence of placenta praevia.

The aim of the study was to compare the single pregnancy and neonate outcome after fresh and frozen-thawed embryo transfer in the in vitro fertilization programme (IVF). The study focused on clinical and laboratory factors affecting the abnormal placentation, especially placenta praevia, in patients conceiving in the IVF programme. The results confirm that neonates born after frozen-thawed embryo transfer had significantly higher mean birth weight than after fresh embryo transfer (ET). Moreover, the birth weight distribution in singletons was found to shift towards "large for gestation" (LGA) after frozen-thawed ET. On the other hand, the pregnancies after fresh ET were characterized by a higher incidence of placenta praevia and 3rd trimester bleeding. Placenta praevia was more common in IVF patients with fresh ET in a stimulated cycle than in patients with ET in a spontaneous cycle. It occurred more frequently in patients with transfer of 2 embryos. From this point of view, single ET and ET in a spontaneous cycle should be encouraged in good prognosis patients in the future with more than two good quality embryos developed. An important issue arose of how the ovarian hormonal stimulation relates to abnormal placentation and if the serum hormone levels interfere with in the IVF treatment results.