Файл: Medical_Myths_Lies_and_Half-Truths_guidebook.pdf

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Lecture 21: What Placebos Can and Cannot Do

Medical advances can largely be understood as progressively moving 
away from placebo interventions to biologically active and science-based 
interventions. But at the same time, ironically, we are trying to understand 
those aspects of placebo effects that are genuinely helpful. It may seem 
contradictory: We are using placebos as a very important tool for removing 
illusions and misdirections from our understanding of what works and what 
doesn’t work. At the same time, we are trying to exploit bene

¿

 cial aspects of 

placebo effects to maximize patient healing, reduce symptoms, and improve 
quality of life. It should be kept in mind that all of the bene

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 ts that you can 

get from placebo effects you will also get from treatments that are science 
based and actually work. 

Ŷ

Benedetti, 

Placebo Effects

.

Price, Finniss, and Benedetti, “A Comprehensive Review of the 
Placebo Effect.” 

1. 

What causes placebo effects? 

2. 

Do you think a placebo effect is suf

¿

cient to justify a 

medical intervention?

3. 

Do physicians commonly prescribe placebos?

    Questions to Consider

    Suggested Reading

79

Myths about Pregnancy 

Lecture 22

It’s expected that mothers who are pregnant will gain weight from the 
pregnancy itself. But how much weight gain is healthy or appropriate? 
It’s not necessary actually for a woman to signi

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 cantly increase her 

intake of food. An additional 300 calories per day is the average need of 
a pregnant woman in order to get all the nutrition that she needs.

P

regnancy is a powerfully emotional event in our lives, for the women 
who become pregnant, but also for every family member. It’s no 
surprise that when pregnancy comes up, friends and relatives come 

out of the woodwork with medical advice. But is this advice true, or is much 
of it myth? 

Many beliefs and advice center on how to get pregnant in the 

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 rst place. 

The reality of getting pregnant is that timing is everything. The egg and the 
sperm have to be in the same place at the same time. If you achieve this, 
fertilization occurs with a 30% success rate. 

There are some other variables, however, that people consider to increase 
the odds of getting pregnant. Does position matter? The bottom line is no, at 
least not to the probability of getting pregnant. Should you save up sperm? It 
turns out that maximum sperm counts occur at about 48 hours, so there is no 
point in saving up beyond a 48-hour time period. There’s also no evidence 
that moving around after sex reduces the chances of conception. You may 
have heard that if the man sits in a hot tub, that will reduce the chance of 
conception. That is true; heat does reduce the sperm count slightly.

Once a woman is pregnant, we often want to predict the sex of the child. There 
are scienti

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 c ways to do this. An example is ultrasound, which allows us to 

determine the sex with about 93% accuracy. But there is a lot of folklore that 
pretends to be able to determine what the sex of the child will be. For example, 
carrying low is supposed to indicate a boy, and carrying high is supposed to 
predict a girl. Actually, how a woman carries is determined by muscle tone and 
baby position; it has nothing to do with the gender of the fetus. 

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Lecture 22: Myths about Pregnancy 

Another myth is that if the mother is craving sweets, she will have a girl. If 
she is craving salty foods, she will have a boy. Most pregnant women report 
that they do have cravings. This is due to altered taste and smell, though there 
may be other factors like nutritional needs that are not completely clear in the 
research. However, these cravings bear no relationship to the sex of the child.

What about choosing the sex? Some couples may not want to just predict 
what sex of child they’re going to have; they may want to actually determine 

whether they have a boy or a 
girl. There are many folklore 
beliefs about this. Many of them 
involve timing, such as whether 
conception occurs during the 
day or at night. There are myths 

about conceiving during a full moon or in a particular position. Other 
myths involve foods that the mother eats at or around the time of 
conception. None of these folklore beliefs have any validity in science
or medicine. 

Once a couple has achieved pregnancy, of course, they want to have the 
healthiest pregnancy possible. This is another source of many beliefs about 
pregnancy. A healthful diet for the mother is de

¿

 nitely healthy for the baby. 

Let me go over some nutritional details that are legitimate. You may have 
heard that 

¿

 sh is brain food and therefore is good for mothers to eat while 

they’re pregnant. This is true, but seafood may also contain mercury. While 

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 sh is a good source of certain nutrients during pregnancy, pregnant women 

should avoid sword

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 sh, shark, and white tuna and should eat no more than 

12 ounces of 

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 sh per week. 

In order to have a healthy pregnancy, there are certain foods that should be 
avoided. These include unpasteurized milk; soft cheeses such as feta, Brie, or 
Roquefort unless the label says it’s made with pasteurized milk; refrigerated 
meat spreads or pâtés; and hot dogs and deli meats, unless they are very 
thoroughly steamed.

What about alcohol? We cannot say, based on the evidence, what a safe level 
of alcohol is during pregnancy. Therefore, it’s best to just avoid it completely. 

The evidence for the effects of 
caffeine is actually quite mixed.

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What about caffeine in pregnancy? The evidence for the effects of caffeine 
is actually quite mixed. In order to be conservative, it is recommended that 
pregnant women take less than 200 milligrams of caffeine per day, which is 
about the amount of caffeine you would get in a 12-ounce coffee. 

What about other exposures during pregnancy? Accutane, which is a 
drug commonly used to treat acne, increases the number of birth defects. 
Therefore, Accutane should not be used during pregnancy or even while 
trying to become pregnant. Another thing that women should avoid is nail 
polish. Nail polish contains phthalates, which are endocrine disruptors and 
may interfere with certain hormones. What about using a hair dryer? That is 
safe, as is hair dye. 

There have been some concerns raised about pregnant women sitting in 
front of a computer monitor for hours at a time. There is no evidence or 
theoretical basis for any health concerns from using computers. However, 
pregnant women are at higher risk of developing carpal tunnel syndrome. 
This is because their tissues tend to retain more 

À

 uid. 

What about air travel—should pregnant women restrict their air travel? The 
increased exposure to radiation is minimal and of no health concern. But 
there are legitimate health concerns from long 

À

 ights. One is to make sure 

that you keep well hydrated. Also, you should get up and walk around the 
cabin as often as possible to prevent the occurrence of blood clots in your 
legs from stasis. 

Another genuine risk to pregnancy is smoking. Smoking inputs toxins into 
the body and can be associated with decreased fetal weight and premature 
birth. These factors are in turn associated with learning disabilities, increased 
risk of cerebral palsy, and lifelong problems. 

Ŷ

Bouchez, “Separating Pregnancy Myths and Facts.” 

Harms and Mayo Clinic, 

Mayo Clinic Guide to a Healthy Pregnancy.

Stone and Eddleman, 

The Pregnancy Bible

.

    Suggested Reading

82

Lecture 22: Myths about Pregnancy

1. 

What are the ways you can predict or determine the sex of a child before 
it is born?

2. 

What do you really need to know to have a safe pregnancy? 

    Questions to Consider