If You’re Eating for Two, Why Are You Vomiting?

One of the most com­mon symp­toms of ear­ly preg­nan­cy in human beings is nau­sea and vom­it­ing. Why do so many preg­nant women have so much trou­ble keep­ing food down at the very time that their need for calo­ries and oth­er nutri­ents has just gone up? Why is this prob­lem com­mon in women but seem­ing­ly nonex­is­tent in preg­nant females of oth­er species? Is there some­thing wrong with the design of human preg­nan­cy, or is there some­thing wrong with the food the preg­nant woman is eat­ing? I’m inclined to sus­pect the food, espe­cial­ly because morn­ing sick­ness is com­mon in the Unit­ed States but rare to nonex­is­tent in soci­eties whose sta­ple foods all come from plants.

Vom­it­ing is a pow­er­ful defense mech­a­nism. It effec­tive­ly removes tox­ins and infec­tious agents from the stom­ach and even the upper intestines. It’s nature’s way of expelling things that shouldn’t be allowed to enter the body. This defense mech­a­nism may be par­tic­u­lar­ly impor­tant dur­ing preg­nan­cy. Stud­ies have con­sis­tent­ly shown that women who vom­it dur­ing ear­ly preg­nan­cy are less like­ly to have a mis­car­riage than are those who mere­ly feel nau­se­at­ed. Per­haps it’s because the vom­it­ing pre­vent­ed things that would be harm­ful dur­ing ear­ly preg­nan­cy from enter­ing the woman’s body. Thus, it’s prob­a­bly no coin­ci­dence that the nau­sea and vom­it­ing asso­ci­at­ed with preg­nan­cy tend to be most severe dur­ing the first trimester, which is the most sen­si­tive phase of devel­op­ment.

In a clas­sic arti­cle, Samuel Flax­man and Paul Sher­man explained how morn­ing sick­ness could end up pro­tect­ing the moth­er and the preg­nan­cy. They argued that morn­ing sick­ness is most com­mon when the major organ sys­tems are devel­op­ing, and the vom­it­ing seems to be trig­gered by the foods and bev­er­ages that are most like­ly to be harm­ful to the moth­er and the preg­nan­cy. Flax­man and Sher­man point­ed out that in 9 out of 9 stud­ies, women who expe­ri­enced morn­ing sick­ness were much less like­ly to mis­car­ry.

Flax­man and Sher­man not­ed that many preg­nant women have aver­sions to alco­holic and non­al­co­holic (main­ly caf­feinat­ed) bev­er­ages and strong-tast­ing veg­eta­bles, but the great­est aver­sions were to meats, fish, poul­try, and eggs. The impor­tance of ani­mal-based foods in caus­ing morn­ing sick­ness also became obvi­ous in a cross-cul­tur­al com­par­i­son. Sev­en soci­eties that were free of morn­ing sick­ness were sig­nif­i­cant­ly less like­ly to have ani­mal foods as dietary sta­ples and were sig­nif­i­cant­ly more like­ly to have only plants (main­ly corn) as sta­ple foods than were 20 soci­eties in which women expe­ri­ence morn­ing sick­ness.

Food­borne infec­tious or par­a­sitic dis­ease could be a seri­ous threat to the health of a preg­nant woman or her preg­nan­cy. Dur­ing preg­nan­cy, a woman’s immune sys­tem is already some­what sup­pressed, to keep it from attack­ing the preg­nan­cy. As a result, preg­nant women are more like­ly to catch seri­ous, poten­tial­ly dead­ly infec­tions. Infec­tious and par­a­sitic dis­eases are also a major threat to the devel­op­ing embryo. For exam­ple, if a preg­nant woman catch­es Tox­o­plas­ma, which is a par­a­site found in cat drop­pings or under­cooked beef, the par­a­site infec­tion could cause mis­car­riage, still­birth, or severe birth defects.

A preg­nant woman can pro­tect her health and her preg­nan­cy by sim­ply avoid­ing the foods that are like­ly to make her vom­it. A pure­ly plant-based diet pro­vides all of the nutri­ents that a preg­nant woman needs, except for vit­a­min D (which she can get from sun­shine) and vit­a­min B12 (which is made by bac­te­ria and is avail­able in a nice, clean tablet).

Pho­to by Tip­sTime­sAd­min

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