The American College of Nurse Midwives reports that 25 percent of pregnant women experience some nausea during pregnancy (without vomiting), and 50 percent will have both nausea and vomiting during the first 16 weeks. Nausea and vomiting are the cardinal symptoms of what is commonly referred to as "morning sickness." The phenomenon is so common that women often suspect that they are pregnant when morning sickness occurs, sometimes before the pregnancy has been confirmed. There is still no definitive proof of the cause of morning sickness, but it is believed that rising levels of the pregnancy hormone HCG play a role in the appearance of symptoms.
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Aversion to Smells
Often unusual and sudden aversion to specific smells is a very early symptom of morning sickness. Explanation of this phenomenon is largely speculative. However, aversion to certain smells is believed to indicate that the substance in question poses a threat to the pregnancy. This seems like a logical explanation, considering some of the common offensive substances: cigarette smoke, charred or raw meat, alcohol and coffee.
Nausea and queasiness are among the first signs of morning sickness. It is not uncommon for nurses and doctors to hear patients report that nausea is harder to cope with than vomiting. Unfortunately, about 25 percent of pregnant women will suffer with queasiness until it subsides, somehow, without vomiting. Both the American Academy of Family Physicians and the National Institutes of Health explain that nausea associated with morning sickness is likely caused by hormones.
Aversion to Foods
Many women can attest to the peculiar aversion to specific foods, which often coincides with the onset of morning sickness. Like the aforementioned aversion to specific smells, a woman's sudden aversion to foods that she previously enjoyed is often a first sign of morning sickness. It is speculated that this aversion may be an instinctual response that protects pregnancy by ensuring that a woman avoids foods that are potentially harmful to the developing fetus. Foods that are commonly cited as triggers of aversion are often greasy, spicy or highly processed.
Vomiting in the absence of illness is typically one of the first signs of morning sickness. When coping with unpredictable aversions to smells and food, not to mention hours of nausea, it is not surprising that vomiting ensues. Nausea and vomiting during the first few months of pregnancy can occur at any time of day, although these symptoms are most common soon after waking. A late or missed menstrual period in a woman of childbearing age, along with nausea and vomiting, is often the first sign of pregnancy.
Women experiencing early signs associated with morning sickness should consult a physician, especially in the absence of a menstrual period. Home pregnancy tests are relatively inexpensive, widely available, easy to use and mostly reliable when performed according to the instructions. It is a good idea to seek prenatal care as early as possible. In a confirmed pregnancy, the National Institutes of Health advise that women contact their doctor if morning sickness does not subside, lasts more than 16 weeks, if blood is vomited or if vomiting occurs more than three times a day.