Morning Sickness in Pregnant Women Functions for Toxic Avoidance

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Morning sickness is a term to describe the ill feeling experienced by pregnant women who are in their first trimester of pregnancy. The ill feeling is better defined as food aversions, nausea and vomiting. It is termed ‘morning sickness’ because many women experience it upon rising (Profet, 1995); but in reality, morning sickness could happen at any time of the day. So the term morning sickness may be a misnomer. There are many other terms used including nausea and vomiting in pregnancy (NVP) rather than morning sickness (Flaxman & Sherman, 2000). The term NVP will be used throughout this essay. Generally, everyone has a toxin tolerance threshold to detect level of toxicity in their blood; and if this threshold is exceeded, will induce nausea and vomiting. Similarly, NVP is when the usual threshold of tolerance to toxin is lowered; thus increasing the sensitivity in detecting toxin levels in the maternal blood to protect the embryo (Profet, 1995). There have been much speculations on the main causes of NVP and to how well it benefits both the mother and the embryo. Many studies claim that NVP functions for toxic avoidance although the depth of this claim is yet to be proven. In this essay, I am reviewing studies on NVP; and discussing if NVP is an evolutionary act to protect the embryo.

The symptoms of NVP peak during embryonic organogenesis (weeks 6-18) because this is when the embryo is most susceptible to chemical disruption (Flaxman & Sherman, 2000). Organogenesis is the period of organ formation from the tissue layers ectoderm, mesoderm and endoderm. Physically expelling out intolerable foods and feeling nausea are the obvious signs of NVP. Commonly known as a short-term sickness designed for a long-term benefit, NVP begins...

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