首先我要感谢home99。她提出的这个B超的危害问题。虽然实际妈妈们不用怕。但是这个质疑精神是非常非常好的。正是我们从正常中发现不正常，从当然中发现不当然，我们的科学才进步，我们对世界的认识才不断更新。好了拍够了home99 mm的马屁，让我们来看看这个超声诊断到底如何。有兴趣的mm就都读一读，没有的就看看中文部分应该也可以。
以下是引用home99 mm的一段。当然我发现这段是从网上抄的。但是转抄的人很多，所以mm是言之有据的：（言之无据的是那帮记者）
“为什么超声波检查过多不利于胎儿生长呢？这是因为超声波的探头在胎头部位停留时间过长，超声波可造成大脑一时性抑制。对女胎来说，超声波还可抑制卵巢的发育。劳伦斯教授对澳大利亚2800名孕妇的观察结果证实，虽然怀孕18-38周的孕妇进行多次超声波检查并不影响自身的健康，但至少有33%的胎儿的生长发育受到不同程度的抑制。”
上文”劳伦斯教授对澳大利亚2800名孕妇的观察结果“的实际的报告在这里：NewnhamJP, Evans SF, Michael CA, Stanley FJ, landau LI: Effects of Frequent Ultrasound during Pregnancy: A Randomised Control Trial. Lancet 1993, 342:887-891.
由于这篇文章在所有中文网站上一再被引用，就让我们一起来看一看。文章发表在1993年的柳叶刀杂志，绝不是什么垃圾报告，而是发表在顶尖医学杂志上的严肃科学论文。既然是科学论文，就让我们一起科学地看看它。在这篇报告中作者将2834名患者，好吧是正常孕妇，不是患者分为两组，一组是大剂量B超外加连续波超声多普勒管道流量测量（continuous-wave Doppler flow），另一组只接受一次B超。在mm的年龄，身高，体重，等等等等都一样的情况下，作者发现大剂量B超组新生儿体重小于10%的要多一些。原话是这样的：The proportion of liveborn infants with birthweights < 10th centile was greater in the intensive group of the trial (relative risk 1-35; 95% confidence intervals 1-09 to 1-67; p = 0006) as was birthweight <3rd centile (relative risk 1-65; 95% confidence intervals 1-09 to 2-49; p = 0.020). 但是下面紧接着一句是：The mean birthweight in the intensive group was 25 g less than in the regular group, although this difference was not statistically significant. 就是说大剂量组的宝宝有更高的比例体重在10%以下。但是平均而言大剂量组只比正常剂量组的宝宝小25克，而且没有统计意义。也就是说平均体重而言，两者没有差别。另外下面继续分析道：Multiple logistic regression analyses determined the effect of group allocation with other factors which may influence fetal growth (table 2). Statistically significant and independent effects on the probability of birth weight < 3rd centile were observed for allocation to the intensive arm of the trial (p = 0.009), gestational age at birth (p < 0.0001), smoking practice (p < 0.001), obstetric intervention (p < 0.001) and maternal age (p = 0.035). Analysis for the probability of birthweight < 10th centile showed the same variables to have significant effects and the adjusted odds ratio (95% confidence interval) for allocation to the intensive arm was 1 46 (1 -14 to 1-87). If obstetric intervention was considered as an outcome rather than a confounding factor, removal of this variable from the model did not alter the coefficients of the other parameters. 什么意思呢？请英语好的同学帮忙给翻译一下。我的理解是不能排除分组，抽烟等其他因素的影响。
最后作者总结道：Our findings suggest that five or more ultrasound imaging and Doppler flow studies between 18 and 38 weeks gestation, when compared with a single imaging study at 18 weeks gestation, increases the proportion of growthrestricted fetuses by about one third. It must be appreciated, however, that the purpose of this study was to investigate another hypothesis and it remains possible that the effect on birthweight percentiles was due to chance alone because this was not the principal endpoint under investigation. Nevertheless, our analyses have been unable to identify any other factors which could explain the observed effects on fetal growth. A large randomised controlled trial is now required which has been designed specifically to investigate the effects of ultrasound exposure on fetal growth. Such a study would appear to be ethical because the results of the present study do not indicate that any alteration in fetal growth is accompanied by excess neonatal morbidity or mortality. In the meantime it would seem prudent to limit ultrasound examinations of the fetus to those cases in which the information is likely to be of clinical importance.
意思是说除了本调查是为其他目的设置的，而分组误差的可能不能排除。
好了这篇文章看完了。呼，让我歇口气。下面继续说。
我不是做超声研究的，所以还是让我们来看看其他专家是如何看待这个问题的。这是一篇review paper，发表于2006年的progress inbiophysics and molecular biology 93 (2007) 295-300。他的abstract是这么写的：Epidemiological studies have indicated no association between diagnostic ultrasound exposure during pregnancy and childhood malignancies. Diagnostic ultrasound imaging does not seem to influence birth weight, whereas frequent Doppler ultrasound was associated with reduced birth weight in one study. Most experts do not believe that ultrasound exposure during pregnancy is associated with reduced birth weight. There are no confirmed statistically significant associations between ultrasound and dyslexia and neurological development during childhood. However, two randomised controlled trials and two cohort studies have been unable to rule out a possible association between ultrasound and left-handedness among males.
全文如此，一字未少。意思是说超声首先不会致畸。然后是超声不影响婴儿体重，只有澳洲的一个研究显示经常使用多普勒超声有可能与出生体重较轻有关联。然后是超声与神经发育，阅读困难没有关系。最后是不能排除与男孩子的左撇子有关。
关于婴儿体重问题，文章中是这么说的：Human birth weight data have been reported in many epidemiological studies (Bakketeig et al., 1984; Davies et al., 1992; Eik-Nes et al., 1984; Ewigman et al., 1990; Geerts et al., 1996; Lyons et al., 1988; Moore et al., 1988; Newnham et al., 1993; Saari-Kemppainen et al., 1990; Scheidt et al., 1978; Stark et al., 1984; Waldenstro¨m et al., 1988), and only one study (Newnham et al., 1993) has created some concern.
也就是说，关于婴儿体重和超声的关系有很多相关研究，只有澳大利亚的这个找到差别。即使如此，文章接着说道：Results from the Australian trial are inconsistent with the available data on birth weight from other randomised trials of diagnostic imaging ultrasound (Bakketeig et al., 1984; Eik-Nes et al., 1984; Ewigman et al., 1990; Geerts et al., 1996; Saari-Kemppainen et al., 1990; Waldenstro¨m et al., 1988). Those studies have been summarized in a Cochrane review (Neilson, 1998), which concludes that there is no statistically significant difference in the proportion of low birth weight children (o2.5 kg) between ultrasound-screened children and controls (odds ratio 0.96, 95% confidence interval 0.82–1.12).
就是说他们澳洲的数据与其他研究的数据不符。并且澳洲的同一个组follow up了8年这些宝宝。发现他们在体重，身高，头围等各个方面都没有差别。
再来看看这个澳大利亚的调查。以下是澳大利亚超声医学会于1988年发表的关于B超安全的声明。
A statement was released by the Australian Society for Ultrasound in Medicine in 1988:
" Diagnostic Ultrasound has been in clinical use since the late 1950's. To date the results of numerous follow-up studies on patients and children who had been examined before birth have failed to demonstrate any biological effect which could be attributed to the ultrasound examination. Given the known benefits and demonstrated efficacy of the medical diagnosis, the Australian Society for Ultrasound in Medicine considers that the prudent use of diagnostic ultrasound far outweigh the risks, if any, that may be present. There is no reason to withhold the application of the technique when it is indicated on clinical grounds. "
就是这样一篇严肃认真的文章，到了记者们手中就成了对B超安全性的质疑。其实这也容易理解，就像negative的results发不了好paper一样，证明B超无害的文章也上不了news，记者们也要吃饭，希望大家理解。
综合来说，就是临床诊断用的超声，经过很多大型的研究都认为对宝宝和妈妈是安全的。完全不用担心。
但是，如果那个医生据此建议孕妈妈没事常来诊所做超声玩儿，我建议你赶紧换医生。因为超声是诊断工具，完全只有在合格的医生手中才能用，才有用。绝对，绝对，绝对不是床头玩具。滥用超声只是说明这个医生或者是不知道如何使用超声，或者是浪费医疗资源。但是妈妈们可以放心，至少是对宝宝so far so good。
再次感谢home99 mm
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