The first subject I want to address is one that may surprise some people – ultrasounds.
Decades ago, people thought x-rays were safe enough to be used in shoe stores and on pregnant women, and the general populace did not sufficiently question the safety of routine use of a technology approved (implicitly if not explicitly) by the medical profession. Similarly, we have insufficient evidence to conclusively determine that the benefits of routine use of ultrasound technology outweigh its risks. We as the medical profession have accepted the use of ultrasounds for every pregnant woman, and it is for that reason that nearly every layperson considers them normal and safe. A simple internet search will tell you over and over that the evidence is lacking, and medical associations do not recommend routine ultrasonography. According to the Society for Maternal-Fetal Medicine, “a fetal ultrasound with detailed anatomic examination […] is not necessary as a routine scan for all pregnancies” and, “has also determined that no more than 1 fetal ultrasound with detailed anatomic examination is necessary per pregnancy, per practice, when medically necessary (SMFM, 2004)”. The American College of Obstetricians and Gynecologists stated, "The use of either two-dimensional or three-dimensional ultrasonography only to view the fetus, obtain a picture of the fetus, or determine the fetal sex without a medical indication is inappropriate and contrary to responsible medical practice" (ACOG 2009). 
Somehow, despite these recommendations, health care providers in the field of obstetrics continue to routinely offer and use ultrasonography. Perhaps the problem is that we as providers are uninformed, or perhaps it is simply difficult to resist using technology that offers such an amazing view. There are certainly a great many people who love using technology merely because we have it, holding a “why not?” view on technology. In doing so, however, we are doing a serious disservice to our patients, who are commonly much less informed than we are and who trust us to provide safe treatment.
If you are wondering what the dangers of ultrasonography may be, there is an excellent, detailed article from Midwifery Today describing the risks associated with ultrasounds . The short version is that ultrasound waves have been linked to low birth weights, brain cell damage, and even (possibly) autism spectrum disorders. I have hypothesized, though I have not yet found any research on the subject, that the excessive use of ultrasonography may one day be linked to the increased incidences of ADHD as well as autism (ASD).
Please understand, the last thing I want to do is be yet another voice preaching at pregnant women that yet another thing is dangerous to their babies. As a nurse, I constantly emphasize to my patients that they need to educate themselves and become an informed and participative patient, and that is extremely important for pregnant women too, since we know there are things that can have lifelong consequences for a child exposed in utero. I have included several links below to help people begin to inform themselves.
1. An article (with references to multiple studies) from the Association for Improvements in the Maternity Services (U.K.), 2004: http://www.aims.org.uk/Journal/Vol16No4/ultrasound.htm
2. A study on ultrasounds from the Society of Gynecologists & Obstetricians of Canada, 2005: http://www.sogc.org/guidelines/public/160E-CPG-June2005.pdf