1) Morning sickness --> another pearl from evolutionary medicine.
Nausea and vomiting (n/v) in early pregnancy are so common --> they are regarded as almost physiological.
But could they have an evolutionary benefit?
Nausea and vomiting (n/v) in early pregnancy are so common --> they are regarded as almost physiological.
But could they have an evolutionary benefit?
2) Firstly, its not called morning sickness anymore.
Its n/v of pregnancy aka NVP.
Why?
Because it takes place at all times of the day and night.
Its n/v of pregnancy aka NVP.
Why?
Because it takes place at all times of the day and night.
3) We have a graphical representation of the usual course of NVP here. 
4) Why does NVP happen?
First of all, NVP does not seem to be common among other mammals (caveat being that very little research has been done on this).
Yet it occurs in upto 90% of human pregnancies!
First of all, NVP does not seem to be common among other mammals (caveat being that very little research has been done on this).
Yet it occurs in upto 90% of human pregnancies!
5) It is believed that NVP causes an aversion to meat, fish, poultry eggs and other strong tasting vegetables in pregnant women.
These may contain harmful toxins and microbes that can harm the pregnant woman or the fetus!
These may contain harmful toxins and microbes that can harm the pregnant woman or the fetus!
6) What is the proof?
1. NVP peaks during the period of embryonic organogenesis ie between weeks 6 and 18 of pregnancy.
Look at tweet 3!
1. NVP peaks during the period of embryonic organogenesis ie between weeks 6 and 18 of pregnancy.
Look at tweet 3!
7) 2. Women who experience NVP are significantly less likely to miscarry!
In fact, women who vomit experience even lesser rates of spontaneous abortion than women who are just nauseated!
In fact, women who vomit experience even lesser rates of spontaneous abortion than women who are just nauseated!
8) 3. Aversion to foods like meat, fish, poultry and eggs is understandable --> these were most likely to contain pathogenic organisms and toxins!
Examples --> Listeria and Salmonella!
ncbi.nlm.nih.gov/pmc/articles/P…
Examples --> Listeria and Salmonella!
ncbi.nlm.nih.gov/pmc/articles/P…
9) 4. Traditional societies with plant based diets are almost immune to NVP!
These theories were presented by two evolutionary biologists from Cornell University --> SM Flaxman and PW Sherman in 2000!
pubmed.ncbi.nlm.nih.gov/10858967/
These theories were presented by two evolutionary biologists from Cornell University --> SM Flaxman and PW Sherman in 2000!
pubmed.ncbi.nlm.nih.gov/10858967/
10) What are the other theories behind NVP?
1. Genetic conflict theory --> that NVP is a byproduct of maternal-fetal genetic conflict --> it is triggered by increasing beta HCG levels --> but NVP peaks ahead of the beta HCG peak --> it leads, where it should lag!
1. Genetic conflict theory --> that NVP is a byproduct of maternal-fetal genetic conflict --> it is triggered by increasing beta HCG levels --> but NVP peaks ahead of the beta HCG peak --> it leads, where it should lag!
11) But this relationship is not 100% proved.
It is believed that different beta HCG isoforms +/- receptor sensitivity may alter the risk of developing NVP!
ncbi.nlm.nih.gov/pmc/articles/P…
It is believed that different beta HCG isoforms +/- receptor sensitivity may alter the risk of developing NVP!
ncbi.nlm.nih.gov/pmc/articles/P…
12)
2. It is believed that NVP signals to other males and kin that the woman is pregnant --> it signs low sexual activity and need for help.
But sexual activity may not be dangerous during the 1st trimester --> the time of peak NVP incidence!
2. It is believed that NVP signals to other males and kin that the woman is pregnant --> it signs low sexual activity and need for help.
But sexual activity may not be dangerous during the 1st trimester --> the time of peak NVP incidence!
13)
3. Some early studies proposed that NVP may be a psychosomatic illness --> it is a manifestation of a pregnant woman's desire to reject her fetus --> they found that women with NVP had a higher rates of unplanned/undesired pregnancies.
pubmed.ncbi.nlm.nih.gov/6743596/
3. Some early studies proposed that NVP may be a psychosomatic illness --> it is a manifestation of a pregnant woman's desire to reject her fetus --> they found that women with NVP had a higher rates of unplanned/undesired pregnancies.
pubmed.ncbi.nlm.nih.gov/6743596/
14) As you can see, NVP is far from a cut and dried topic!
Theories abound!
But this should not distract from the fact this is a clinical situation which ranges from merely troublesome to life threatening ie hyperemesis gravidarum!
Theories abound!
But this should not distract from the fact this is a clinical situation which ranges from merely troublesome to life threatening ie hyperemesis gravidarum!
I hope you liked this small window into evolutionary medicine!
Please share/retweet if you do!
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Please share/retweet if you do!
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