Introduction: The method of carrying out PTB is one of the most controversial topics of modern perinatology, because there are no clear and undeniable works and studies that would in any case support vaginal delivery (VD) or delivery to the cesarean section (CS). Aim: To determine more frequent mode of delivery in different groups of birth weights and degrees of prematurity from single and twin pregnancies. To determine the degree of vitality of premature born vaginal delivery (VD) in relation to the cesarean section (CS) in different degrees of prematurity from single and twin pregnancies. Patients and methods: Research has retrospective cohort character. Data were collected from the databases of University Clinic of Gynecology and Obstetrics Tuzla for the period of five years (January 1st, 2012–December 31st, 2016). The study included newborns of both genders, gestational age from 24 to 37 weeks of gestation (WG) in singleton and twin pregnancies. Results: Out of 19506 births, 1350 (6.92%) were preterm birth (PTB). Singleton PTB was 1180 (87.40%), and the twins were 170 (12.59%). Vaginal delivery (VD) was born 788 (58.37%). Cesarean section (CS) was born 562 (41.63%). There was statistically significant association between the mode of delivery (MD) in singleton and twins pregnancy in all three subgroups of birth weight (BW) 1000-1499, 2000-2499 and >2500 grams in 33-37 WG. In this group was more frequent VD than CS mode of singleton delivery, and CS than VD mode of twins delivery. In contrast to newborn with BW 1500-1999 grams (chi-square = 23.16, P <0.0001) in same gestational period where was more frequent CS than VD (OR: 2.56, 95% CI: 1.71-3,85). Apgar score (AS) at first and five minute 5-7 and 8-10 in the period 28-32 and 33-37 was a statistically significant frequent in VD and singletons in contrast to CS and twins. Conclusion: VD was more frequent in the higher WG, as well as the higher AS in singletons in contrast to twins delivery.

Amira Peco-Antić, University Children’s Hospital, 10 Tiršova Street, SER-11000 Belgrade (Serbia) Dear Sir, In uremic patients, hemodialysis (HD) may change plasma endothelin 1 (ET-1) levels [1, 2], but, at present, little is known about its causes and consequences. The aims of this study were to estimate the effect of volume depletion and blood depuration on plasma ET-1 concentration during HD and to evaluate the potential importance of ET-1 as the modulating cardiovascular hormone in blood pressure control and myocardial hypertrophy. Plasma levels of ET-1 were measured in 10 children with terminal renal failure (mean age 14.7 ± 5.1 years) studied 1-157 months (mean 40.6 ± 52.6), undergoing chronic HD with acetate or bicarbonate dialysis fluid and cuprophane suitable hollow disposable dialyzers. The clinical characteristics of the patients are summarized in table 1. Six patients were treated with nifedi-pine and captopril due to arterial hypertension. Blood samples were taken during a single dialysis session: before ultrafiltration, after ultrafiltration and after HD without fluid removal. Initially, the patients were only on ultrafiltration without dialysis until they achieved ‘dry weight’ or until symptoms of hypotension appeared. After that they continued dialysis without ultrafiltration for at least 2 h. For ET-1 measurements, blood samples were collected in tubes containing aprotinin (Bayer, Leverkusen, Germany; Trasylol, 500 KlU/ml of blood) and EDTA (7.5 mmoy∏il of blood) and immediately centrifuged at +4°C. The plasma samples were stored at -80 °C until assayed. Plasma ET-1 concentrations were measured by radioimmunoas-say (RIA) using a commercially available kit (Biomedica, Vienna, Austria), after extraction with Amprep C 18 columns that were preequilibrated with methanol and water. Plasma renin activity was measured by an angiotensin I RIA kit (SB REN 2, Cis bio international). M mode echocardiography was used to determine left ventricle dimensions. Left ventricle mass was calculated according to the Penn convention [3]. The left ventricular mass index was obtained by normalization of left ventricle mass to body surface.