Elevated maternal midtrimester serum free beta-human chorionic gonadotropin levels in vegetarian pregnancies that cause increased false-positive Down syndrome screening results.
OBJECTIVE
The aim of this study was to examine whether midtrimester maternal serum free beta-human chorionic gonadotropin and alpha-fetoprotein levels for Down syndrome screening differed in vegetarian pregnancies and omnivore pregnancies and to evaluate whether maternal serum vitamin B(12) concentration affected these maker levels.


METHODS
Ninety-eight vegetarian and 122 omnivore singleton pregnancies were studied. Reference levels of free beta-human chorionic gonadotropin and alpha-fetoprotein were based on a population of 6312 singleton euploid pregnancies that had been surveyed previously. Serum free beta-human chorionic gonadotropin and alpha-fetoprotein levels were measured by enzyme immunoassay or radioimmunoassay. Multiples of the median values were calculated to determine whether different diet habits affected serum biomarker levels. Maternal serum vitamin B(12) levels were determined with radioimmunoassay.


RESULTS
The free beta-human chorionic gonadotropin multiples of the median values were elevated significantly in the vegetarian pregnancies group (1.28 multiples of the median) compared with that of the reference population (1.00 multiples of the median) (P<.001). A negative association between the serum free beta-human chorionic gonadotropin multiples of the median values and the concentration of maternal serum vitamin B(12) was observed in the vegetarian pregnancies. No correlation was found between the alpha-fetoprotein multiples of the median values and the maternal serum vitamin B(12) concentration.


CONCLUSIONS
The current data showed that the midtrimester maternal serum free beta-human chorionic gonadotropin levels increased in vegetarian pregnancies and led to an elevated false-positive rate in screening for Down syndrome compared with pregnant women with regular diet and resulted in unnecessary invasive procedures. It is necessary to establish vegetarian pregnancy alpha-fetoprotein and beta-human chorionic gonadotropin reference levels to correct increased false-positive screening results.
Department of Obstetrics and Gynecology, Chang Gung Memorial Hospital, Taipei, Taiwan. pjcheng@cgmh.org.tw
Po-Jen
PJ
Cheng
Da-Chang
DC
Chu
Ho-Yen
HY
Chueh
Lai-Chu
LC
See
Hsing-Chen
HC
Chang
David Red-Helm
DR
Weng
D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood*; D014676:Diet, Vegetarian; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D014805:Vitamin B 12 / Q000097:blood; D000509:alpha-Fetoproteins / Q000032:analysis*
D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D014805:Vitamin B 12