Morning sickness is common in pregnant women; it is sometimes a misnomer too.
Technically speaking, nausea in pregnancy is what we understand by morning sickness, although the discomfort tends to last throughout the day.
You might feel a certain level of discomfort even at night or in the evening.
However, the symptoms are known to be at its worst in the morning.
More than 3/4 of the pregnant women tend to develop this typical habit of nausea during the first trimester.
Pregnancy nausea when it starts is first time around the sixth week, but it might also develop in the fourth week.
It further worsens over the months.
Pregnancy nausea when at its worst can lead to heath complications.
While some women are relieved much earlier during the pregnancy, some others have to wait till the time they deliver the baby.
It is only post delivery that they get some relief from nausea.
The Cause of Pregnancy Nausea What causes morning sickness or nausea in pregnant women is still not known for sure.
Experts have often related the combined effects of physical and hormonal changes to be one of the common factors of morning sickness in pregnant women.
Some of the possible causes could be:

• Fast increasing levels of hormone, particular the hCG hormone during the first few weeks of pregnancy.
  Although it isn't still clear as to how hCG contributes to morning sickness, it is often presumed to be a common reason behind the condition.
  Nausea is usually at its peak during that time.
  Another hormone that is presumed to be a cause of nausea is estrogen.
  Hormones do play a major role.
  
• During pregnancy women usually develop an enhanced sensitivity to smell and odors.
  Women at their very first stages of pregnancy often feel overwhelmeddue to the smell of certain foods; not only foods, there could be many such odors that tends to trigger their senses and in turn fiddles with their gag reflex.
  This causes a sudden rise in the estrogen hormone levels thereby leading to nausea.
  
• Some women often have an over sensitive digestive system that it at its worst during pregnancy.
  These women usually develop morning sickness that lasts all through the condition.
  

Pregnancy nausea can begin at any point of time and it is never in your control.
All you can do is to cope up with it all through the 9 months.
Sometimes vitamin B supplements are suggested to women for an improved condition, although it is often said that vitamin B deficiency is the major cause of nausea, it might not be the same all the time.
There could be one or more than one reason why women get morning sickness.
It is also suggested that multivitamins can be a great relief for nausea during pregnancy.
Although it does provide relief, according to research, but why so is still not clear to us.
Another research has proposed that there are certain women who are actually psychologically predisposed to developing vomiting and nausea during pregnancy and it could be due to an abnormal way of responding to stress and anxiety.
The truth is that pregnancy nausea when it begins is at its worst for the women experiencing it.
There isn't too any other way but to bear it.