When nausea and vomiting occurs in pregnancy, it is termed as morning sickness. Although, it does not do justice to its name, as apart from only morning, it can happen at any time of the day. Morning sickness is a very common symptom experienced by pregnant women, found in about 80% of women. Women under the age of 25 years are more likely to have morning sickness than older women. It is mostly seen around the first trimester and early second trimester of pregnancy; however, in some women it may exist throughout the pregnancy, until delivery of child. Nausea and vomiting can range from mild to severe; the severe form known as hyperemesis gravidarum. In hyperemesis gravidarum, the vomiting can be so severe that the patient may have to be hospitalized. It can also lead to imbalance in electrolyte profile, weight loss, and malnutrition that can have adverse effect in both the mother and the fetus.
Is Morning Sickness A Good Sign?
Nausea and vomiting is always distressing, be it any moment, pregnant or not. No matter how distressing it is, it can be seen in 4 out of 5 pregnant women. This has made everyone wonder, even doctors and researchers whether this distressing feeling could be a good sign of a viable pregnancy. Folklore had it for ages that morning sickness is a good sign; however, it was never backed by science. In recent decades, this belief has been validated by research and science that morning sickness can actually be a good sign.
The association of nausea and vomiting in pregnancy to lower risk of miscarriage has been backed by very strong proof validated by research. Nausea and vomiting has been shown to have protective effect on the developing fetus. This has been associated with human chorionic gonadotrophin hormone and also the evolutionary effect that prompts to eat a low risk and healthy diet for the fetus.
Of note, it is important not to be disheartened if one does not experience nausea and vomiting. Not having morning sickness does not mean termination of pregnancy or miscarriage.
Morning sickness could also be related to urinary tract infection. Pregnant women should be wary of severe nausea and vomiting that might leave them malnourished and electrolyte loss in body. Morning sickness should be considered a thing of pregnancy and just overlooked. It should be prevented, especially if caused by hyperemesis gravidarum or other cause such as UTI and treatment should be provided in such cases to prevent any risk to mother or the developing baby.
Even after all these years of technical and scientific advancement, there is still lack of consensus and validating proof behind the exact cause of morning sickness. One such hypothesis shows that nausea and vomiting is hereditary and runs in family, whether it is mild nausea and vomiting or is more severe form of nausea and vomiting, i.e., hyperemesis gravidarum. Another hypothesis suggests the increased levels of hCG (human chorionic gonadotrophin) to be the cause of nausea and vomiting during pregnancy. This is based on the observation of elevated levels of hCG coinciding with nausea and vomiting and alleviating levels of the hormone with resolution of nausea and vomiting in pregnant women, which happens around early second trimester or end of first trimester.
Recent study and research has linked nausea and vomiting to several genes and presence of a protein GDF15 that is produced in high amounts by placenta in early pregnancy. This protein is linked to the food center and vomiting center of the brainstem, leading to reduced food intake and increased sense of nausea and vomiting. GDF15 protein has been found in greater concentrations in pregnant women with nausea and vomiting.
Another hypothesis connects it to evolutionary mechanism by protecting the developing fetus from any toxins or pathogens via food being ingested by the mother during the first trimester, which is the most important phase of organ development.
- Fejzo, M. S., Ingles, S. A., Wilson, M., Wang, W., MacGibbon, K., Romero, R., … & Mullin, P. M. (2018). High prevalence of severe nausea and vomiting of pregnancy and hyperemesis gravidarum among relatives of affected individuals. European journal of obstetrics & gynecology and reproductive biology, 221, 153-157.
- Gazmararian, J. A., Petersen, R., Jamieson, D. J., Schild, L., Adams, M. M., Deshpande, A. D., & Franks, A. L. (2002). Hospitalizations during pregnancy among managed care enrollees. Obstetrics & Gynecology, 100(1), 94-100.
- Klonoff-Cohen, H., & Lam-Kruglick, P. (2001). Maternal and paternal recreational drug use and sudden infant death syndrome. Archives of pediatrics & adolescent medicine, 155(7), 765-770.
- Fejzo, M. S., Magtira, A., Schoenberg, F. P., & MacGibbon, K. W. (2019). Incidence of Hereditary Thrombophilias in Hyperemesis Gravidarum. Cureus, 11(11).
- Saito, S., & Nakashima, A. (2010). A review of the mechanism for poor placentation in early-onset preeclampsia: the role of autophagy in trophoblast invasion and vascular remodeling. Journal of Reproductive Immunology, 85(1), 1-7.
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