The Relationship Of The Start Of Nausea And Vomiting Of Pregnancy (NVP) To The Isoform Of hCG In Maternal Blood.

The Relationship Of The Start Of Nausea And Vomiting Of Pregnancy (NVP) To The  Isoform Of hCG In Maternal Blood.

Early pregnancy produces a type of hCG that resembles in terms of immunoreactivity, a major form of hCG excreted in Choriocarcinoma known as isoform ß152. This isoform predominates in maternal blood for the first 5-6 weeks of gestation and is then replaced by a less glycosylated hCG known as ß109 increasingly which predominates until 11 weeks of gestation (1).

Carbohydrate moieties such as glycols and sialic acid appear to be related to bioactivity of hCG. Indeed N-linked oligosaccharides in the a chain (ASN) of hCG play an important role in signal transduction resulting in a stimulation of steroid genesis and Adenosine 3’ 5’ monophosphate (cyclic AMP) production (2). There was a higher proportion of ß152 like hCG isoforms when hCG secretion was low in very early pregnancy (2).

There was a strong negative correlation between the isotopes of hCG ß152/ß109 and gestational age of women between 32 and 50 days from the first day of last menstrual period (LMP) (3). There is also a considerable increase of ß109 hCG with reduction of ß152 being produced from the early trophoblast at this early stage of pregnancy (3). This altered glycosylation of ß109 hCG compared to ß152 hCG is associated with altered bioactivity of hCG (2) and might be related to the development of nausea and vomiting of pregnancy NVP.

The week in which NVP most frequently started was week 6 or more specifically, day 39 from LMP (4). This is the week in which there is a significant fall in the ratio between hyperglycosylated hCG and regular hCG from 87% hyperglycosylated hCG in days 21-27 to 43% hyperglycosylated hCG in days 35-41 from LMP (3) and there is at the same gestational time an enormous rise in maternal serum hCG (3) suggesting a relationship between regular hCG and the start of nausea and vomiting of pregnancy.

REFERENCES

1. KOVALEVSKAY G., BIRKEN S., KAKUHA T., O’CONNOR J.F.
Early Pregnancy Human Chorionic Gonadotrophin (hCG) isoforms measured by immunometric assay for Choriocarcinoma – like hCG.
J. Endocrinol 1999; 161:99-106

2. MOCK P., KOVALEVSKAYA G., O’CONNOR J.F., CAMPARA A.
Choriocarcinoma – like Human Chorionic Gonadotrophin (hCG) and hCG bioactivity during the first trimester of pregnancy.
Human Reprod. 2000; 15(10):2209-2214

3. COLE L.A.
Biological functions of hCG & hCG related molecules.
Reprod. Biol Endocrinol 2010; 8, 102
http://www.rbej.com/contents/8/1/102

4. GADSBY R., BARNIE-ADSHEAD A.M., JAGGER C.
A prospective study of nausea and vomiting during pregnancy.
British Journal of General Practice 1993; 43, 245-248

 

 

Did you know?

Hyperemesis Gravidarum rarely ends at 12 weeks of pregnancy. It typically improves in the middle of pregnancy, but symptoms often last until birth.

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