Morning sickness

Morning sickness
Mild hyperemesis gravidarum (no metabolic derangement)
Classification and external resources
ICD-10 O21.0
ICD-9 643.0

Morning sickness, also called nausea gravidarum, nausea, vomiting of pregnancy (emesis gravidarum or NVP), or pregnancy sickness is a condition that affects more than half of all pregnant women. Related to increased estrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or hormone replacement therapy. Sometimes it is present in the early hours of the morning and reduces as the day progresses. The nausea can be mild or induce actual vomiting, however, not severe enough to cause metabolic derangement. In more severe cases, vomiting may cause dehydration, weight loss, alkalosis and hypokalemia. This condition is known as hyperemesis gravidarum and occurs in about 1% of all pregnancies. Nausea and vomiting can be one of the first signs of pregnancy and usually begins around the 6th week of pregnancy (counting gestational age from 14 days before conception). In spite of its common name, it can occur at any time of the day, and for most women it may stop around the 12th week of pregnancy.



Proximate causes of pregnancy sickness include:

  • An increase in the circulating level of the hormone estrogen. Estrogen levels may increase by up to a hundredfold during pregnancy.[1][unreliable source] However, there is no consistent evidence of differences in estrogen levels and levels of bilirubin between women that experience sickness and those that do not.[2]
  • Low blood sugar (hypoglycemia) due to the placenta's draining energy from the mother, though studies have not confirmed this.[3]
  • An increase in progesterone relaxes the muscles in the uterus, which prevents early childbirth, but may also relax the stomach and intestines, leading to excess stomach acids and gastroesophageal reflux disease.
  • An increase in human chorionic gonadotropin. It is probably not the human chorionic gonadotropin itself that causes the nausea. More likely, it is the human chorionic gonadotropin-stimulating the maternal ovaries to secrete estrogen, which in turn causes the nausea.[4]
  • An increase in sensitivity to odors, which overstimulates normal nausea triggers.
  • An increase in bilirubin levels due to increased liver enzymes.

Morning sickness as a defense mechanism

Morning sickness is currently believed to be an evolved trait that protects the fetus against toxins ingested by the mother.[5] [6] Many plants contain chemical toxins that serve as a deterrent to being eaten. Adult humans, like other animals, have defenses against plant toxins, including extensive arrays of detoxification enzymes manufactured by the liver and the surface tissues of various other organs. In the fetus, these defenses are not yet fully developed, and even small doses of plant toxins that have negligible effects on the adult can be harmful or lethal to the embryo.[7] Pregnancy sickness causes women to experience nausea when exposed to the smell or taste of foods that are likely to contain toxins injurious to the fetus, even though they may be harmless to her.

There is considerable evidence in support of this theory, including:[8] [9]

  • Morning sickness is very common among pregnant women, which argues in favor of its being a functional adaptation and against the idea that it is a pathology.
  • Fetal vulnerability to toxins peaks at around 3 months, which is also the time of peak susceptibility to morning sickness.
  • There is a good correlation between toxin concentrations in foods, and the tastes and odors that cause revulsion.

Women who have no morning sickness are more likely to miscarry.[10] This may because such women are more likely to ingest substances that are harmful to the fetus.[11]

In addition to protecting the fetus, morning sickness may also protect the mother. Pregnant women's immune systems are suppressed during pregnancy, it is presumed to reduce the chances of rejecting tissues of their own offspring.[12] Because of this, animal products containing parasites and harmful bacteria can be especially dangerous to pregnant women. There is evidence that morning sickness is often triggered by animal products including meat and fish.[13]

If morning sickness is a defense mechanism against the ingestion of toxins, the prescribing of anti-nausea medication to pregnant women may have the undesired side effect of causing birth defects or miscarriages by encouraging harmful dietary choices.[8] On the other hand, many domestic vegetables have been purposely bred to have lower levels of toxins than in the distant past, and so the level of threat to the embryo may not be as high as it was when the defense mechanism first evolved.[14]


There is no evidence to demonstrate the effectiveness of treatments for morning sickness.[15] Suggested treatments typically aim to lessen the symptoms of nausea, rather than attacking the root cause(s) of the nausea. Treatments include:

  • Wearing acupressure wristbands to stimulate the "Nei-Kuan" acupuncture point on your wrist. [16][17][18][19][20]
  • Lemons, in particular the smelling of freshly cut lemons.
  • Avoiding an empty stomach.
  • Accommodating food cravings and aversions.
  • Eating five or six small meals per day, rather than three large ones.
  • Eating cabbage.[21]
  • Ginger, in capsules, tea, ginger ale, or ginger snaps.[22] Prepare ginger tea by putting ginger shreds in a glass of hot water. Take sips of the tea until nausea is relieved. Ginger candy and capsules are also great alternatives to stop nausea.[23][medical citation needed]
  • Eating dry crackers in the morning. Some women benefit from eating crackers before rising out of bed in the morning.
  • Drinking liquids 30 to 45 minutes after eating solid food.
  • If liquids are vomited, sucking ice cubes made from water or fruit juice or trying lollipops.

A doctor may prescribe anti-nausea medications if the expectant mother suffers from dehydration or malnutrition as a result of her morning sickness, a condition known as hyperemesis gravidarum. In the US, Zofran (ondansetron) is the usual drug of choice, though the high cost is prohibitive for some women; in the UK, older drugs with which there is a greater experience of use in pregnancy are preferred, with first choice being promethazine otherwise as second choice metoclopramide, or prochlorperazine.[24] When all other treatments fail, doctors may consider trying a corticosteroid medication such as methylprednisolone.[25] This medication can be given orally or intravenously. It should not be used before 10 weeks gestation because of a small risk that it could cause a cleft lip or palate in the fetus. Because of possible maternal complications, the medicine should not be used for longer than six weeks.


Thalidomide was originally developed and prescribed as a cure for morning sickness in West Germany, but its use was discontinued when it was found to cause birth defects. The United States Food and Drug Administration never approved thalidomide for use as a cure for morning sickness.


  • Morning Sickness: A Comprehensive Guide to the Causes and Treatments, Nicky Wesson, Vermilion (1997), ISBN 009181538X
  • Morning Sickness - A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References, Icon Health Publications (2004), ISBN 0597840431


  1. ^ "First Trimester Pregnancy". The Visible Embryo. Retrieved 2008-07-06. 
  2. ^ n Elizabeth Bauchner; Wendy Marquez. "Morning Sickness: Coping With The Worst". NY Metro Parents Magazine. Retrieved 2008-07-06. 
  3. ^ Erick, Miriam (2004). Managing Morning Sickness: A Survival Guide for Pregnant Women. Bull Publishing Company. ISBN 0923521828. Retrieved 2008-07-06. 
  4. ^ Niebyl, Jennifer R. (2010). "Nausea and Vomiting in Pregnancy". New England Journal of Medicine 363 (16): 1544–1550. doi:10.1056/NEJMcp1003896. PMID 20942670. 
  5. ^ Hook, E. B. (1976). "Changes in tobacco smoking and ingestion of alcohol and caffeinated beverages during early pregnancy: are these consequences, in part, of feto-protective mechanisms diminishing maternal exposure to embryotoxins?". In Kelly, S.. Birth Defects: Risks and Consequences. Academic Press. pp. 173–181. 
  6. ^ Profet, Margie (1992). "Pregnancy Sickness as Adaptation: A Deterrent to Maternal Ingestion of Teratogens". In Barkow, Jerome; Cosmides; Tooby, Leda. The Adapted Mind: Evolutionary Psychology and the Generation of Culture. Oxford University Press. pp. 327–365. 
  7. ^ Beck, F. (1973). Human Embryology and Genetics. Blackwell Scientific. 
  8. ^ a b Nesse, Randolphe M; Williams, George C (1996). Why We Get Sick (First ed.). New York: Vintage Books. pp. 290. 
  9. ^ Pepper, GV; Roberts, Gillian V. (2006). "Rates of nausea and vomiting in pregnancy and dietary characteristics across populations". Proceedings of the Royal Society B 273 (1601): 2675–2679. doi:10.1098/rsbp.2006.3633. PMC 1635459. PMID 17002954. 
  10. ^ Chan, Ronna L. et al.; Olshan, A. F.; Savitz, D. A.; Herring, A. H.; Daniels, J. L.; Peterson, H. B.; Martin, S. L. (Sept. 22, 2010). "Severity and duration of nausea and vomiting symptoms in pregnancy and spontaneous abortion". Human Reproduction 25 (11): 2907–12. doi:10.1093/humrep/deq260. PMC 3140259. PMID 20861299. 
  11. ^ Sherman, Paul W.; Flaxman, Samuel M. (2002). "Nausea and vomiting of pregnancy in an evolutionary perspective". Am J Obstet Gynecol 186 (5): S190–S197. doi:10.1067/mob.2002.122593. PMID 12011885. 
  12. ^ Haig, David (October 1993). "Genetic conflicts in human pregnancy". Quarterly Review of Biology 68 (4): 495–532. doi:10.1086/418300. PMID 8115596. 
  13. ^ Flaxman, Samuel M.; Sherman, Paul W. (June 2000). "Morning sickness: a mechanism for protecting mother and embryo". Quarterly Review of Biology 75 (2): 113–148. doi:10.1086/393377. PMID 10858967. 
  14. ^ Martin, Mike (June 29, 2009). "Margie Profet's Unfinished Symphony". Weekly Scientist. 
  15. ^ Matthews A, Dowswell T, Haas DM, Doyle M, O'Mathúna DP (2010). Matthews, Anne. ed. "Interventions for nausea and vomiting in early pregnancy". Cochrane Database of Systematic Reviews 2010 (9): CD007575. doi:10.1002/14651858.CD007575.pub2. PMID 20824863. 
  16. ^ Werntoft E, Dykes AK. Effect of acupressure on nausea and vomiting during pregnancy. A randomized, placebo-controlled pilot study. Journal of Reproductive Medicine, 2001 46(9):835-9 September
  17. ^ Steele NM, French J, Gatherer-Boyles J, Newman S, Leclaire S. Effect of acupressure by Sea-Bands on nausea and vomiting of pregnancy. Journal of Obstetric, Gynecologic and Neonatal Nursing 2001 Jan-Feb;30(1):61-70
  18. ^ Smith C, Crowther C, Beilby J. Acupuncture to treat nausea and vomiting in early pregnancy: a randomized controlled trial. Birth March 2002; 29(1):1-9
  19. ^ Smith C, Crowther C, Beilby J. Pregnancy outcome following women’s participation in a randomised controlled trial of acupuncture to treat nausea and vomiting in early pregnancy.
  20. ^ Complementary Therapies in Medicine 2002 June;10(2):78-83
  21. ^ Akhtar MS, Munir M (1989). "Evaluation of the gastric anti-ulcerogenic effects of Solanum nigrum, Brassica oleracea and Ocimum basilicum in rats". Journal of ethnopharmacology 27 (1–2): 163–176. doi:10.1016/0378-8741(89)90088-3. PMID 2515396. "Brassica oleracea (leaf) powder did not affect the ulcer index significantly but its aqueous extract lowered the index and increased hexosamine levels, suggesting gastric mucosal protection." 
  22. ^ Borrelli F, Capasso R, Aviello G, Pittler MH, Izzo AA (2005). "Effectiveness and safety of ginger in the treatment of pregnancy-induced nausea and vomiting". Obstetrics and gynecology 105 (4): 849–56. doi:10.1097/01.AOG.0000154890.47642.23. PMID 15802416. 
  23. ^ Lucy Ross. "Pregnancy Nausea Remedies". Retrieved 2011-04-22. 
  24. ^ British National Formulary (March 2003). "4.6 Drugs used in nausea and vertigo - Vomiting of pregnancy". BNF (45 ed.). ISBN 0853694168. 
  25. ^ American College of Obstetricians and Gynecologists. Nausea and Vomiting of Pregnancy. ACOG Practice Bulletin Number 52, April 2004. Reaffirmed 2009.

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Look at other dictionaries:

  • Morning sickness — Morning Morn ing, a. Pertaining to the first part or early part of the day; being in the early part of the day; as, morning dew; morning light; morning service. [1913 Webster] She looks as clear As morning roses newly washed with dew. Shak. [1913 …   The Collaborative International Dictionary of English

  • morning sickness — morning .sickness n [U] a feeling of sickness that some women have during the morning when they are ↑pregnant, usually in the early months …   Dictionary of contemporary English

  • morning sickness — n. a condition of nausea and vomiting, sometimes accompanied by dizziness, headache, etc., that affects many women during the first months of pregnancy: it occurs most often in the morning …   English World dictionary

  • morning sickness — morning ,sickness noun uncount a feeling of wanting to VOMIT that affects some women when they are pregnant …   Usage of the words and phrases in modern English

  • morning sickness — ► NOUN ▪ nausea occurring in the mornings during early pregnancy …   English terms dictionary

  • Morning sickness — Nausea and vomiting of pregnancy. Morning sickness is a misnomer, because it can occur at any time of the day (though not at night during sleep) and it is not a sickness. It is a normal characteristic of early pregnancy. Morning sickness is now… …   Medical dictionary

  • morning sickness — noun nausea early in the day; a characteristic symptom in the early months of pregnancy • Hypernyms: ↑nausea, ↑sickness • Part Holonyms: ↑pregnancy, ↑gestation, ↑maternity * * * noun [noncount] : a feeling of sickness that a pregnant woman may… …   Useful english dictionary

  • morning sickness — N UNCOUNT Morning sickness is a feeling of sickness that some women have, often in the morning, when they are pregnant …   English dictionary

  • morning sickness — (in pregnant women) nausea in the morning, upset stomach often occurring in the morning …   English contemporary dictionary

  • morning sickness — noun (U) a feeling of sickness that some women have before they have a baby …   Longman dictionary of contemporary English

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