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This section contains information about “What causes Pregnancy Sickness” and it has been written with health care professionals in mind. However Pregnancy Sickness Support Trust will not be held responsible for any actions that are taken or not taken based on this information.

 

 

Considering The Evidence

An important question that you might ask is, “What causes Nausea & Vomiting of Pregnancy (NVP)?” Medical research has shown an association between the pregnancy hormone human chorionic gonadotrophin (hCG) and NVP although this association only holds true when several women are grouped together in the investigation, rather than for an individual pregnant woman. In addition, high maternal (mother’s) blood levels of this hormone occur in twin pregnancies and twin pregnancies are generally associated with increased NVP.

• Note: read more in section 1 of the Prostaglandin E2 PDF document.

A rare condition in the Western World is a hydatidiform mole in which the afterbirth is abnormal, but more significantly, there is no normal baby present. This condition is also known to be associated with a high maternal human chorionic gonadotrophin (hCG) blood level and increased NVP. As there is no baby present the NVP cannot arise from the baby. There is one other pregnancy related condition in which high blood levels of hCG occur in women’s blood, but this condition is not associated of itself with any sickness. Therefore, neither the baby nor hCG itself can be the cause of NVP. hCG can be considered to be associated with NVP, but not its actual cause.

• Note: read more in section 1 of the Prostaglandin E2 PDF document.

It is remarkable that the hormone hCG has, by electrophoresis, been shown to occur in at least 5 different isoforms or types. In very early pregnancy the type with the most ‘acidic’ form is more prominent in maternal blood, whereas after 11-15 weeks of pregnancy, the most ‘basic’ form of hCG becomes the prominent type in maternal blood. It has been shown, by further investigation, that the ‘acidic’ form of hCG is the more active type of hormone because it lasts longer in the maternal blood than basic hCG. This active acidic type of hCG has been shown to be present in larger quantities in the maternal blood of women who have hyperemesis gravidarum (the most severe form of pregnancy sickness) than occurs in normal pregnancy.

• Note: read more in section 3 of the Prostaglandin E2 PDF document.

If hCG itself is not causing NVP, though associated with the condition, perhaps some substance that stimulates (increases) hCG synthesis (production) in early pregnancy could cause NVP. At present we know of at least 11 locally acting hormones, which stimulate the secretion and release of hCG from placental (afterbirth) cells.

• Note: read more in section 4 of the Prostaglandin E2 PDF document.

The only two of these known to cause sickness in pregnancy are called Prostaglandin E2 and Prostaglandin F2 alpha.

• Note: read more in section 5 of the Prostaglandin E2 PDF document.

One further investigation has shown that more Prostaglandin E2 is present in maternal blood when a pregnant woman is feeling sick, than when she is not feeling sick on the same day.

• Note: read more in section 11 of the Prostaglandin E2 PDF document.

Obviously, more investigation is needed into this under-funded, and under-researched condition before we can be certain about the association of acidic hCG and Prostaglandin E2 with pregnancy sickness. We have been able to show there are grounds for believing NVP to be a condition based on physical hormones, rather than a purely nervous reaction to a stressful situation.