- 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.[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.
- Low blood sugar (hypoglycemia) due to the placenta's draining energy from the mother, though studies have not confirmed this.
- 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.
- 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.  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. 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.
- 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.
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. 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.
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. 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.
There is no evidence to demonstrate the effectiveness of treatments for morning sickness. 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. 
- 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.
- Ginger, in capsules, tea, ginger ale, or ginger snaps. 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.[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. When all other treatments fail, doctors may consider trying a corticosteroid medication such as methylprednisolone. 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
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Pathology of pregnancy, childbirth and the puerperium (O, 630–679) PregnancyPregnancy with
abortive outcomeOedema, proteinuria and
hypertensive disordersOther, predominantly
related to pregnancyGestational thrombocytopenia · Pregnancy-induced hypercoagulabilityamniotic fluid (Polyhydramnios, Oligohydramnios) · chorion/amnion (Chorioamnionitis, Chorionic hematoma, Premature rupture of membranes, Amniotic band syndrome, Monoamniotic twins) · placenta (Placenta praevia, Placental abruption, Monochorionic twins, Twin-to-twin transfusion syndrome, Circumvallate placenta) · Braxton Hicks contractions · Hemorrhage (Antepartum)
Labor Puerperal Other
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