Nausea and Vomiting During Pregnancy BIOL445- Biology of Toxins Geanna Capitan, Caleb Mangum, Patrick Quintana, Gennifer Smith.

Nausea and Vomiting During Pregnancy

BIOL445- Biology of ToxinsGeanna Capitan, Caleb Mangum, Patrick Quintana, Gennifer

Smith

Why are Nausea and Vomiting Important During Pregnancy?

Expels ingested pathogens, toxins, and possible teratogens Evidence suggest that nausea and vomiting peaks

during the critical development of an embryo to a fetus in the first trimester when organogenesis occurs (Flaxman and Sherman, 2002).

Creates food aversions during pregnancy Helps the mother avoid further ingestion of

pathogens, toxins, and possible teratogens Attempts to get rid of nausea and vomiting

symptoms.

Why are Nausea and Vomiting Important During Pregnancy?

Is nausea and vomiting an evolutionary adaptation? Nausea and vomiting during pregnancy is associated

with positive birth outcomes and decreased fetal mortality. Possibly explained by an adaptation that nausea and vomiting increases fetal maturation by decreasing a mothers nutritional intake (Pepper, 2002).

“A second prominent adaptive explanation for NVP [nausea and vomiting during pregnancy] is that it may serve a prophylactic function against ingestions of potentially harmful foodstuffs” (Pepper, 2002)

What is a toxin?

A substance produced by an organism that has adverse affects on another organism Toxins are often produced by pathogens that enter

the human body

What is a teratogen?

“Terato” = monster

“gen” = making

Teratogen = monster making A substance that causes birth defects

Where are toxins (possible teratogens) found in everyday life?

Foods Caffeine (coffee, tea, soda), meats

(fish, poultry, eggs), alcohol, vegetables, spicy foods, chocolate, dairy

Plants Lupidus, Tansy Ragwort, Cannabis

Medication Streptomycin, Tetracycline, some

Anti-depressants, Progestin and synthetic Estrogen, Accutane (acne medication), Diet Pills, Epilepsy medicine

Where are toxins (possible teratogens) found in everyday life?

Other Nicotine, cookware, improper food

storage techniques

Toxins are everywhere!! Nausea and vomiting during

pregnancy help expel the possible teratogens amongst these toxins. Food aversions help avoid further contact.

Critical Periods of Pregnancy

~40% fertilized eggs make it to birth, 60% do not

First Trimester (conception 3 months) Embryo (weeks 1-8)

During 3rd Week: neural tube forms which will later become brain and spinal cord. Arms, legs & organs start to form

During 6th Week: Sex-determining region Y (SRY) is activated in males (Testis-determining factor (TDF) cascades in development of male) TDF= protein signal that results in

males in humans and some other species

Fetus (8 weeks+) Source: Lewis (2012)

Critical Periods of Pregnancy in Summarized Table

Summarized Table of Critical PeriodsTime in

PregnancyGrowth Development

Conception 2 month

Ears, Eyes, Heart, and Limbs

Conception 5 months

Reproductive system

Throughout entire Pregnancy

Brain (CNS)

Source: Lewis (2012)

What Tissues are Most Susceptible to Teratogens? When?

Abbreviation

Organ

CNS Central Nervous System

H Heart

UL Upper Limbs

Ey Eyes

LL Lower Limbs

T Teeth

P Palate

EG External Genitalia

E Ears

Figure 1. (Sherman and Flaxman ,2002)

Teratogens: their effects and time of riskAGENT POSSIBLE EFFECTS TIME OF RISK

Alcohol Fetal Alcohol Syndrome causes growth retardation, cognitive deficits

Throughout pregnancy

Aspirin Bleeding problems Last month & at birth

LSD Isolated abnormalities Before conception

Lead Death, anemia, mental retardation Throughout pregnancy

Marijuana Unknown long term effects, early neurological problems

Throughout pregnancy

Thalidomide Fetal death, physical and mental abnormalities

First month

Cocaine Spontaneous abortion, neurological problem

Throughout pregnancy

AIDS Growth failure, low birth weight, developmental delay, death from

infection

Throughout pregnancy,During delivery, and during breast feeding

Rubella Mental retardation, physical problem, possible death

1st 3 months, may have effects during later

months

Syphilis Death. Congenital syphilis pre-maturity From 5 months on

Sourc

e:

Nw

oke

(2008

)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Benefits “Expulsion of toxins and possible

teratogens was favored by natural selection as a protective mechanism for both mother and fetus. Increased protection is to help offset the high susceptibility of fetus to teratogens” (Flaxman and Sherman, 2008)

“Absence of nausea and vomiting could be an indication of greater fetal risk . Nausea and vomiting is seen as a good indication of a healthy pregnancy” (Hook, 1976)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Benefits (Continued) “Nausea and vomiting associated pregnancies are

less likely to result in miscarriage, pre-term delivery, and growth retardation” (Furneaux, 2001)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Benefits (Continued):

Decreased nausea and vomiting during pregnancy is correlated with: higher fetal death (Table 1), lower infant birth weight (Table 2), and shorter gestation time (Table 3) – Tierson (1986)

Table 1. Relationship between NVP experience and pregnancy outcome

Outcome None (n = 44)

(%)

Nausea Only (n = 136)

(%)

Vomiting of Pregnancy

(n = 234) (%)

Live Birth (n = 383)

80.0 89.7 95.4

Fetal Death(n= 31)

20.0 10.3 4.7

Source: Tierson (1986)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Table 2. Relationship between nausea and vomiting experience and Infant birth weight

Infant birth weight

None(n = 44)

(%)

Nausea only

(n= 136) (%)

Vomiting of Pregnancy(n = 234)

(%)

All cases (%)

≤ 2750(n = 36)

19.4 5.7 9.8 9.4

>2750(n = 347)

80.6 94.3 90.2 90.6

Source: Tierson (1986)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Table 3. Relationship between nausea and vomiting experience and Length of Gestation

Length of Gestation

None(n = 44)

(%)

Nausea only (n= 136)

(%)

Vomiting of Pregnancy(n = 234)

(%)

All cases (%)

< 37 wk(n = 18)

11.1 1.6 5.4 4.7

≥ 37 wk(n = 365)

88.9 98.6 94.6 95.3

Source: Tierson (1986)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Mechanism Is it evolution or hormonal? Or both? Furneaux et al. (2001) – cause is hormonal: nausea and

vomiting is promoted by secretion of hCG. “Supporters of the endocrine etiology have suggested

several hormones that may contribute to these symptoms [nausea and vomiting]. These include progesterone and estrogen, because these levels increase throughout the duration of pregnancy. However, the secretion of human chorionic gonadotrophin (hCG) by the placental trophoblast has been proposed as the most likely contributor to the etiology of nausea and vomiting. hCG levels rise rapidly in the first trimester and peak between 10 and 12 weeks’ gestation” (Furneaux et al., 2001).

Evolution of Pregnancy: Why does nausea and vomiting occur?

Mechanism Is it evolution or hormonal? Or both? Furneaux et al. (2001) – nausea and vomiting is NOT

due to certain food intakes. (Contradicts Sherman and Flaxman (2002) findings)

“According to Furneaux et al., “An earlier study of 549 pregnant women in a prospective, population-based study found no relationship between nausea and vomiting and the ingestion of certain foods that could produce adverse pregnancy outcomes.” (Furneaux et al, 2001)

Evolution of Pregnancy: Why does nausea and vomiting occur?

Mechanism Is it evolution or hormonal? Or both? Sherman and Flaxman (2002) – cause is evolution:

developing a way to rid the body of toxins and possible teratogens “Food-borne pathogens are by no means evolutionary

novelties. Microorganisms in food would have become problematic for early hominids when they began killing or scavenging game that was too large to consume immediately….We believe that nausea and vomiting of pregnancy originated and has been maintained as a physiological solution to this problem” (Sherman and Flaxman, 2002).

Evolution of Pregnancy: Why does nausea and vomiting occur?

Mechanism Is it evolution or hormonal? Or both?

Furneaux et al. (2001) presents data that supports hormones as the main cause for nausea and vomiting. Sherman and Flaxman (2002) present data that supports evolution as the cause for nausea and vomiting.

These two hypothesis may not be at odds with each other. The development of hormonal response could be from the effects of evolution. For example, could evolution have caused the

increased secretion of hCG over time?

Evolution of Pregnancy: Why do food aversions occur?

There is an association between the occurrence of nausea and food aversions during pregnancy According to Bayley, “there was a temporal

association between the week of first onset of nausea and the week of first occurrence of food aversions. In 64% of cases, the first occurrence of nausea was reported either in the week preceding the first food aversion or in the same week as the first food aversion.”

These findings show that when an illness occurs from a certain food, an aversion learning mechanism for that specific food ensues.

Evolution of Pregnancy: Why do food aversions occur?

Due to nausea and vomiting- body’s desire is to avoid repeated episodes “The mechanism that links nausea and vomiting to

food aversions is that of taste aversion learning. This form of classical conditioning in which an organism comes to avoid food (conditioned stimulus) that has previously been paired with a transient illness” (Bayley, 2002).

When is food aversion the strongest? Why?

Food aversion is strongest in the first trimester

Fetus and mother are most susceptible to teratogens Organs developing

Thalidomide tragedy

“Teratogens are any agents that cause abnormalities and such agents include: drugs, chemicals, infections, maternal health state, alcohol, smoking, and pollutants. Prenatal period is a very sensitive period in the life of the human organism, and the danger of structural defects caused by teratogens is greater in the embryonic stage” (Nwoke, 2008).

When is food aversion the strongest? Why?

Food aversion is strongest in the first trimester Nausea and vomiting occurs in about 80% of

pregnancies. “The severity and frequency of nausea and vomiting is greatest early in gestation during the ‘critical period’”(Hook).

Is nausea and vomiting during pregnancy healthy for the mother and fetus? “Some studies suggest that the absence of nausea and

vomiting is an indication of greater fetal risk” (Hook).

When is food aversion the strongest? Why?

Food aversions decrease over subsequent trimesters and typically disappear completely after birth “Pregnancy-related food aversions wane rapidly and

usually disappear completely after parturition. By contrast, the aversions that men and nonpregnant women develop as a result of food poisoning usually last much longer, sometimes for entire lifetimes” (Sherman and Flaxman, 2002).

What to take away from this

Development of anti-morning sickness drugs Could possibly do more harm than good- nausea

and vomiting can ultimately help protect mother and fetus by ridding body of toxins “The absence of nausea and vomiting could be an

indication of greater fetal risk” (Hook ,1974). “Nausea and vomiting associated pregnancies are less

likely to results in miscarriage, pre-term delivery, and intrauterine growth retardation” (Furneaux et al., 2001).

Drugs could possibly be teratogens themselves – embryonic development is a very sensitive process and easy to disrupt Example: Thalidomide

Unanswered Questions

What about breast-feeding? Lots of toxins can be passed to the baby through

breast milk Why do food aversions typically disappear after birth?

For the best protection, wouldn’t evolution cause them to continue until after breast-feeding?

Or do food aversions disappear because after birth the baby is no longer susceptible to teratogens and is less susceptible to toxins?

Although according to Nwoke: “teratogenic agents can be disastrous to the developing human being from the moment of conception to birth and/or through life “ (Nwoke, 2008)

Unanswered Questions Cont’d

Psychological Adaptations Why do pregnancy-related food aversions typically

disappear after birth while food poisoning-related food aversions can last a life time?

Literature Cited

Bayley, Tracy M., Louise Dye, Susan Jones, Martin DeBono, and Andrew J. Hill. "Food cravings and aversions during pregnancy: relationships with nausea and vomiting." Appetite 38 (2002): 45-51. Print.

Flaxman, Samuel M., and Paul W. Sherman. "Morning Sickness: Adaptive Cause of Nonadaptive Consequence of Embryo Viability." The American Naturalist 172.1 (2008): 54-62. Print.

Furneaux, Edwina C., Alison J. Langley-Evans, and Simon C. Langley-Evans. "Nausea and vomiting of pregnancy: endocrine basis and contribution to pregnancy outcome." Obstetrical & Gynecological Survey 56.12 (2001): 775-782. Print.

Hook, Ernest B.. "Nausea and Vomiting of Pregnancy - a Feto-protective Mechanism Against Embryotoxins." N.Y.S. Dept. of Health, and Dept. of Ped. 4 (1974): 344. Print.

Lewis, R. (2012). Meiosis and Development. Human Genetics: Concepts and Applications (pp. 53-62). New York: McGraw Hill.

Literature Cited Cont’d

Pepper, Gillian V., and S. Craig Roberts. "Rates of Nausea and vomiting in pregnancy and dietary characteristics across populations." Proceedings of the Royal Society 273.1601 (2006): 2675-2679. Print.

Sherman, Paul W., and Samuel M. Flaxman. "Nausea and vomiting of pregnancy in an evolutionary perspective." Journal of Obstetrics & Gynecology 186.5 (2002): 190-197. Print.

Tierson, Forrest D., Carolyn L. Olsen, and Ernest B. Hook. "Nausea and vomiting of pregnancy and association with pregnancy outcome." The American Journal of Obstetrics and Gynecology 155.5 (1986): 1017-1022. Print.

Nwoke, Mary B.. "The Effects of Teratogens on the Health of Developing Human Beings." Paper presented at the 8th Biennial International Conference on Alcohol, Drugs, and Society in Africa 8th (2008): 1-7. Print.