Microwave ovens, satellites, and radio/TV transmission and mobile phone transmitters /receivers produce electromagnetic waves daily. As a matter of fact, we are exposed to electromagnetic waves -apart from the occupational exposure- with a frequency ranging from 300MHz to 300GHz. In addition, the common use of mobile phones has given rise to concerns about the potential influences of electromagnetic waves on human physiology. Worldwide use of mobile phones had been increased by the end of 2008 to about 4.1 billions; these users involve pregnant women also. Several studies have looked into the safety of mobile phones in recent years with uncertain results. There is a growing body of evidence that exposure to high density microwaves can cause detrimental effects to the testis and eyes and induce significant biologic changes involving the central nervous system, cardiovascular system, and hematopoietic system through thermal action. (1,2) Meanwhile, the non-thermal effects of 915MHz microwaves used in mobile phones has been controversial. There is no epidemiologic evidence today showing that occupational or daily life exposures to microwaves do any harm to human reproductive processes (3), but experimental animal studies have suggested that microwaves can produce intra-uterine effects including teratogenic effects. (4,5)
The present study aims to assess the effect of electromagnetic waves of mobile phones on the fetal heart rate as well as fetal perfusion using the CTG monitoring and Doppler ultrasound evaluation.
PATIENTS AND METHODS
This study was conducted in collaboration between the Department of Reproductive Health at the National Research Centre of Cairo, Egypt and a University hospital of Cairo. The bioethical committee at the National Research Centre approved the study. We enrolled 358 normal pregnant women. They were at 28-32 weeks gestation and had no medical disorders or complications of pregnancy. The women were carrying a singleton fetus. We included 187 women in their first pregnancy and 171 multiparous women with age limits between 21 to 35 years. The study had both pregnant women in their first, second or third pregnancy. Their mean age was 27.4 [+ or -] 6.7.
These women had cardiotocography (CTG) monitoring and Doppler ultrasound evaluation while the mobile phones are switched off. Thereafter, the CTG tests were repeated; while the mobile phones were in the dialing mode for 30 minutes, then Doppler ultrasound evaluation was done just after 5 minutes of hanging up the mobile phone to avoid the disturbance of the electromagnetic waves produced by the mobile device on the Doppler machine. The pregnant women enrolled in the study were instructed not to use the mobile phones for 24 hours before carrying out the tests. We ensured the absence of any mobile phones around the examination room within at least 50m. (2) For all women Doppler ultrasound of the umbilical artery was performed using an ultrasound machine (Toshiba Sonace, Korea). The Resistance Index (RI) was traced before and five minutes after using the mobile phone on dialing mode for 30 minutes, to avoid the disturbance in the monitor caused by the mobile phone.
The recorded fetal heart rate strips before and after the mobile phone use were blindly analyzed with respect to baseline fetal heart rate, accelerations, and decelerations.
Data were statistically described in terms of range, mean [+ or -] standard deviation ([+ or -] SD). Comparison of quantitative variables was carried out using Wilcoxon signed rank test for paired (matched) samples. A probability value (P value) less than 0.05 was considered statistically significant.
Fetal heart rate (FHR) baseline was generally higher by 5 beats per minute while using the mobile phones however, this was not statistically significant (P=0.79). Although, the FHR demonstrated an increased number of accelerations while the mothers were talking on the mobile phones as evidenced by more mean numbers of accelerations during exposure than before exposure (1.57 [+ or -] 0.85 vs. 1.14 [+ or -] 0.54, respectively), this difference was not statistically significant.
Nevertheless, the FHR showed higher amplitude of rise while the electromagnetic field was generated than when the phone was switched off. This was statistically significant (19.6 [+ or -] 6.3 vs. 9.3 [+ or -] 3.8; P= 0.01). We did not record any decelerations in the FHR in this cohort of pregnant women whether while the mobile phones were on the dialing mode or switched off. As regards the blood flow through the utero-placental unit, it was evident that the umbilical artery blood flow was not influenced by the electromagnetic waves of the mobile phones. The Doppler RI of the umbilical artery while the mobile phone was not in use was 0.67+ 0.05 however it was 0.67+ 0.04 after usage with no significant difference (P=0.32).
Although there is evidence that the electromagnetic waves produced from mobile phones with low intensity currently used do not exert non-thermal influences on cardiovascular and hormonal parameters of the autonomic nervous system (6), however, the influence on pregnancy and the growing fetus remains to be elucidated. Anatomically the fetus may be in close proximity to the mobile phone while on or stand by modes. There has been continuing concern about possible hazardous effects of electromagnetic waves, due to increased use of mobile phones in pregnancy. Several animal experiments have demonstrated that intrauterine exposures to hyperthermia from microwaves and ultrasound can produce malformations, growth restriction and embryonic loss. Nevertheless, the usual exposure to electromagnetic waves of mobile phones does not result in hyperthermia to the embryo. (7,8)
To the best of our knowledge this is the first study that addresses the effect of the electromagnetic waves emitted off the mobile phones on the fetal perfusion and well being. Our study has shown that although there was no difference in the fetal heart rate baseline or number of accelerations due to mobile phone exposure, the FHR showed higher amplitude of rise while the pregnant women were talking on the mobile phone than while the phone was switched off. This could partly be caused due to the stimulation effect produced by the electromagnetic waves or changing nerve conduction. The same effect on FHR was obtained in Turkey by the study of Celik and Hascalik (9) who found that electromagnetic fields produced by cellular phones do not cause any demonstrable affect in fetal heart rate, acceleration and deceleration. However, the study of Celik and Hascalik studied only 40 pregnant women and the dialing mode was for only five minutes. This may explain the absence of rise of the baseline and number of acceleration we observed in our groups of studied women.
Moustafa and colleagues in a well designed trial involving 12 male human subjects has shown that radiofrequency fields of cellular phones generated free radicals that increased peroxidation in human plasma and decreased the activities of the antioxidant system as superoxide desmolase and total glutathione peroxidase in human erythrocytes. This effect was positively proportional to time. Whenever the balance of antioxidants is outweighed by prooxidizing factors as shown by the radiofrequency of cellular phones, oxidative stress may develop in cells. (10) Furthermore, electromagnetic waves emitted by mobile phones may affect the FHR patterns by means of changing nerve conduction and cardiac contractility. (11) Also, it was shown that low frequency magnetic fields induces a significant increase in the level of corticosterone in blood plasma. (12)
Moreover, there were no detectable differences in the fetal perfusion detected by Doppler resistance index of the umbilical artery. This finding suggests that there is no risk to fetal well being from mobile phone usage in the short term. In addition, this study reassure about the safety of this technology during pregnancy. However, the long term effects of mobile phones’ use on fetus physiology will need further study, as prospective randomized control trials using large numbers of patients, to reach conclusive evidence.
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