Comparison of Cesarean Section and Normal Vaginal Delivery Using Entonox Inhalation in Terms of Oxidative Stress Indices in Newborns and Mothers

According to some studies, fear and pain of normal vaginal delivery (NVD) is the first (1,2) or second (3) reason for cesarean section (CS). Labor pain is a complex, subjective, and multidimensional response to the sensory stimuli during delivery. Labor pain and methods to relieve it are great concerns for pregnant women (2,4). The perspective of medical care systems on labor and labor pain management is progressively relied on anesthetic and analgesic drugs; although there are certain limitations in their medical approval (5). Nitrous oxide has been known as an anesthetic and analgesic for more than 200 years (6). Moreover, N2O is used in pains associated with wound dressing (7), labor pain (8), and labor anxiety (9). N2O is the only inhaled gas that lowers labor pain and is used by midwives in Iran (8). Although 21 studies in a systematic review revealed reduced pain as a result of N2O administration, that study affirmed that N2O cannot be definitively suggested for diminishing pain; as the quality of those studies was under question (10). In some studies, side effects such as dizziness, diarrhea, and vertigo were reported (11). Studies on different methods of labor such as CS (4,8) and painless labor reported different findings regarding maternal oxidative stress. For instance, a study on selective CS and its comparison with a control group (vaginal labor) indicated that the content of degradation products from lipids was greater in women undergoing CS than that in the control group (12). Oxidative stress results from an imbalance between the production of free radicals and active oxygen species on the one hand and their neutralization by antioxidant defense system on the other hand (13). The existence of mitochondria-rich cells and free DNAs in the placenta (14-16) can affect the abundant production of free radical species. These free radicals play an important role in the health of reproductive system. Oxygen radicals influence ovarian production of estrogens, corpus luteum function, and oocyte maturation. The main complications of oxidative stress include impaired function of the endothelial cells, hypertension (17), clinical symptoms of preeclampsia (18,19), intrauterine growth restriction, and low birth weight (20-22). Since no study has compared the indices of oxidative stress in various delivery methods such as CS and NVD using Entonox, this article was conducted to measure the above-mentioned indices. Abstract Objectives: Introduction: Review of articles point out that the route of delivery may cause oxidative stress. Since management of labor is of great importance for healthy childbearing, the present study was performed to compare cesarean section (CS) and normal vaginal delivery (NVD) through Entonox inhalation in terms of oxidative stress indices in mode of delivery. Materials and Methods: Sixty women undergoing CS and 60 women undergoing painless labor using Entonox gas were included in the study after obtaining a written informed consent. Three tests including lipid peroxidation, total thiol molecules (TTMs), and ferric reducing ability of plasma (FRAP) assay were performed. To this end, venous blood samples (5 mL) were obtained from the mothers at the end of the second stage of labor or after surgery. The same indices were measured for 5 mL of blood sample taken from the umbilical artery of the infants. Descriptive (means) and analytical (independent t test) tests were employed for data analysis. Results: Mean maternal lipid peroxidation level in the CS and Entonox groups were 5.798 ± 4.210 and 5.105 ± 2.892 nmol/mm, respectively (P = 0.544). TTMs were 0.2846 ± 0.2632 and 0.2656 ± 0.2437 mmol/mm in the CS and Entonox groups (P = 0.687). Moreover, mean scores of FRAP were 0.766 ± 0.516 and 1.057 ± 0.626 nmol/mm in the CS and Entonox groups, respectively (P = 0.007). However, oxidative stress indices of the infants were not different between 2 groups (P > 0.05). Conclusion: Since total antioxidant capacity in the CS group was lower compared to the Entonox group, it seems that maternal antioxidant defense decreases. Thus, Entonox can be used safely from the perspective of oxidative stress indices.