Why Morning Sickness?

Why Morning Sickness?

It is very common in early pregnancy to have morning sickness, and most of us have endured that aspect of pregnancy.  The main reason for the term “morning sickness” is because it really does tend to come on during the morning hours and then usually improves steadily throughout the day.  Not everyone has the same routine, however, as many complain of evening sickness.  It really can pop up at virtually anytime of the day.

When experiencing the pregnancy sickness, about 50% of pregnant women only feel nauseous while half will experience vomiting.  There are about 1 in 100 who are sick enough that they require hospitalization.  I for one can definitely relate to the women constantly plagued by the vomiting – morning, noon and night!

Thank heavens this sickness usually eases and passes on after the fourth month, but for some it can continue throughout the pregnancy.  For years it has been debated what the cause of morning sickness really is.  Is it hormonal changes in the first 12 weeks or fluctuations in estrogen, progesterone and human chronic gonadotropin that is involved?  There is also a common theory that it evolves as a mechanism to steer pregnant women away from foods that might carry risks.  This sickness will usually peak at about 3 months, which is the time when a fetus is most vulnerable to toxins.

In looking at all the information, it appears that morning sickness is actually a link to a healthy pregnancy.  To date, the studies whether this is true or not have not had a sufficient level of detail.  Stefanie N Hinkle, Ph.D, a staff scientist in the National Institutes of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Epidemiology Branch and first author of the present study, indicates that there wasn’t a lot of high-quality evidence to support this belief.

NICHD completed a study that reopened this question and was published in JAMA Internal Medicine.  They set out to test this theory in more depth: does the presence of morning sickness signal a reduced risk of pregnancy loss?  The team used data from the Effects of Aspirin in Gestation and Reproduction trial.  This data was designed to test the effects of low-dose aspirin on women who had experienced one or two pregnancy losses in the past.  Each participant kept a diary and noted their feelings of nausea between weeks 2 and 8 of their pregnancy.  They completed a monthly questionnaire on their symptoms up until the 36th week of their pregnancies.

The studies completed previously had relied on women’s recollections of sickness symptoms much later in pregnancy, or after they had lost a pregnancy.  This particular study was the first to track morning sickness in real time.  There were 797 pregnant women in the trial of which 188 of them ended in loss.  About 57.3% of the women had reported having experienced nausea, and 26.6% reported experiencing nausea and vomiting by the 8th week.  This analysis revealed that the women who experienced morning sickness were 50-75% less likely to experience pregnancy loss than those who had neither vomiting nor nausea.

I guess those of us that experience this sickness during pregnancy, should accept this as a healthy baby to come!  That makes it all worthwhile!

-Dr Fredda Branyon

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