Morning sickness

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Morning sickness
Classification and external resources
Specialty Obstetrics
ICD-10 O21.0
ICD-9-CM 643.0
MedlinePlus 003119

Morning sickness, also called nausea and vomiting of pregnancy (NVP), nausea gravidarum, emesis gravidarum, and pregnancy sickness, is a pregnancy discomfort that affects more than half of all pregnant women. Symptoms may be present early in the morning and reduce as the day progresses. However, in spite of its common name, nausea and vomiting of pregnancy can occur at any time during the day. For most women the sickness ends around the 12th week of pregnancy (the end of the first trimester).

Related to increased estrogen levels, a similar form of nausea is also seen in some women who use hormonal contraception or hormone replacement therapy. The nausea can be mild or induce actual vomiting. In more severe cases, vomiting may cause dehydration, weight loss, high blood pH, and a low level of potassium in the blood. 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 begin around the 6th week of pregnancy (counting gestational age from 14 days before conception).


Pathophysiology of vomiting in pregnancy

Proximate causes of pregnancy sickness include:

Defense mechanism[edit]

Morning sickness may be an evolved trait that protects the baby against toxins ingested by the mother. Evidence in support of this theory, including:[6][7]

  • 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.[8] This may be because such women are more likely to ingest substances that are harmful to the fetus.[9]

In addition to protecting the fetus, morning sickness may also protect the mother. A pregnant woman's immune system is suppressed during pregnancy, presumably to reduce the chances of rejecting tissues of her own offspring.[10] 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.[11]

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.[6]


There is unclear evidence about the effectiveness of home treatments for morning sickness.[12]


A number of antiemetics are effective and safe in pregnancy including: pyridoxine/doxylamine, antihistamines (such as diphenhydramine), metoclopramide, and phenothiazines (such as promethazine).[13][14] With respect to effectiveness it is unknown if one is superior to another.[13] In the United States and Canada, the doxylamine-pyridoxine combination (as Diclegis in US and Diclectin in Canada) is the only approved pregnancy category "A" prescription treatment for nausea and vomiting of pregnancy.[14]

Ondansetron may be beneficial, but there are some concerns regarding an association with cleft palate,[15] and there is little high quality data.[13] Metoclopramide is also used and relatively well tolerated.[16] Evidence for the use of corticosteroids is weak.[17]

Alternative medicine[edit]

There is tentative evidence that ginger may be useful; however, it is not clear.[18][19] Safety concerns have been raised regarding its anticoagulant properties.[20][21]



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.


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  2. ^ 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 0-923521-82-8. Retrieved 2008-07-06. 
  4. ^ "Hypoglycemia in Type 1 Diabetic Pregnancy". Diabetes Care. March 2010. Retrieved 2013-10-02. 
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  6. ^ a b Nesse, Randolphe M; Williams, George C (1996). Why We Get Sick (1st ed.). New York: Vintage Books. p. 290. 
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  8. ^ Chan, Ronna L.; Olshan, A. F.; Savitz, D. A.; Herring, A. H.; Daniels, J. L.; Peterson, H. B.; Martin, S. L.; et al. (Sep 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. 
  9. ^ 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. 
  10. ^ Haig, David (October 1993). "Genetic conflicts in human pregnancy". Quarterly Review of Biology 68 (4): 495–532. doi:10.1086/418300. PMID 8115596. 
  11. ^ 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. 
  12. ^ Matthews, A.; Haas, D. M.; O'Mathúna, D. N. P.; Dowswell, T.; Doyle, M. (2014). "Interventions for nausea and vomiting in early pregnancy". The Cochrane Library. doi:10.1002/14651858.CD007575.pub3. 
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  14. ^ a b Clark SM, Dutta E, Hankins GD (September 2014). "The outpatient management and special considerations of nausea and vomiting in pregnancy". Semin Perinatol. S0146-0005 (14): 00102–5. doi:10.1053/j.semperi.2014.08.014. PMID 25267280. 
  15. ^ Koren, G (October 2012). "Motherisk update. Is ondansetron safe for use during pregnancy?". Canadian Family Physician 58 (10): 1092–3. PMC 3470505. PMID 23064917. 
  16. ^ Tan, PC; Omar, SZ (April 2011). "Contemporary approaches to hyperemesis during pregnancy.". Current opinion in obstetrics & gynecology 23 (2): 87–93. doi:10.1097/GCO.0b013e328342d208. PMID 21297474. 
  17. ^ Poon, SL (October 2011). "Towards evidence-based emergency medicine: Best BETs from the Manchester Royal Infirmary. BET 2: Steroid therapy in the treatment of intractable hyperemesis gravidarum.". Emergency medicine journal : EMJ 28 (10): 898–900. doi:10.1136/emermed-2011-200636. PMID 21918097. 
  18. ^ Matthews, A; Haas, DM; O'Mathúna, DP; Dowswell, T; Doyle, M (21 March 2014). "Interventions for nausea and vomiting in early pregnancy.". The Cochrane database of systematic reviews 3: CD007575. PMID 24659261. 
  19. ^ Thomson, M.; Corbin, R.; Leung, L. (2014). "Effects of Ginger for Nausea and Vomiting in Early Pregnancy: A Meta-Analysis". The Journal of the American Board of Family Medicine 27 (1): 115–122. doi:10.3122/jabfm.2014.01.130167. ISSN 1557-2625. 
  20. ^ 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. 
  21. ^ Tiran, Denise (Feb 2012). "Ginger to reduce nausea and vomiting during pregnancy: Evidence of effectiveness is not the same as proof of safety". Complementary Therapies in Clinical Practice 18 (1): 22–25. doi:10.1016/j.ctcp.2011.08.007. ISSN 1744-3881.