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.

STUDY

DESIGN

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.

CONCLUSION

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.