title: Transfer of folic acid inside the first-trimester gestational sac and the effect of maternal smoking.
abstract: OBJECTIVE
  The objective of the study was to investigate the transfer pathways of folic acid inside the first-trimester gestational sac and to evaluate the impact of maternal smoking.
  
  
  METHODS
  Folate and cotinine levels were evaluated in maternal serum (n = 125) and coelomic fluid (n = 42), and immunostaining was used to identify folate receptors in placental villi, decidual tissue, and secondary yolk sacs from normal pregnancies at 6-12 weeks' gestation.
  
  
  RESULTS
  Folate receptors-alpha were found on the apical surface of syncytiotrophoblast, uterine glandular epithelial cells, and mesothelial layer of the yolk sac. Significantly higher (P < .05) median folate levels were found in maternal serum than in coelomic fluid. The median folate maternal serum and coelomic levels were significantly (P < .0001 and P < .005) lower in smokers, compared with nonsmokers.
  
  
  CONCLUSIONS
  Uterine glands and the secondary yolk sac play key roles in supplying folic acid to the developing fetus before the placental circulations are established, and maternal smoking does not seem to impair directly its transfer mechanism in early pregnancy.
authors.affiliation: Academic Department of Obstetrics and Gynaecology, Royal Free and University College London Medical School, London, United Kingdom. e.jauniaux@ucl.ac.uk
authors.forename: Eric
authors.initials: E
authors.lastname: Jauniaux
authors.forename: Jemma
authors.initials: J
authors.lastname: Johns
authors.forename: Beatrice
authors.initials: B
authors.lastname: Gulbis
authors.forename: Olivera
authors.initials: O
authors.lastname: Spasic-Boskovic
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Burton
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D002824:Chorionic Villi / Q000378:metabolism; D003367:Cotinine / Q000097:blood; D005260:Female; D058973:Folate Receptors, GPI-Anchored; D005492:Folic Acid / Q000097:blood / Q000378:metabolism*; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D008659:Metabolic Diseases / Q000209:etiology; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012907:Smoking / Q000009:adverse effects*; D014327:Trophoblasts / Q000378:metabolism; D015017:Yolk Sac / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D058973:Folate Receptors, GPI-Anchored; D011956:Receptors, Cell Surface; D005492:Folic Acid; D003367:Cotinine