title: Are amniotic fluid alpha-fetoprotein levels influenced by the gender in twin pairs?
abstract: OBJECTIVE
  To examine the assumption that amniotic fluid alpha-fetoprotein (AFAFP) levels are different in female and male twin fetuses.
  
  
  METHODS
  Amniotic fluid levels of AFP in pregnancies with female and male fetuses in gender-concordant and gender-discordant twins were compared. A t test of p < 0.05 was considered significant.
  
  
  METHODS
  Between 1995 and 1999, 332 genetic amniocenteses on twin pregnancies were performed at Meir Hospital, Kfar Saba, and Rambam Hospital, Haifa, Israel. One hundred and sixty-six were concordant for gender (84 females and 82 males) while 166 pairs differed in their gender. The amniotic fluid AFP levels of each sac were measured using fluorescent immunoassay methods by an AutoDELFIA machine.
  
  
  RESULTS
  The mean levels of AFAFP were lower in female twins compared to their male counterparts in same-gender twins (p = 0.07), although the difference was quite small. Nevertheless, there was no such difference between AFAFP of male versus female fetuses in gender-discordant twins.
  
  
  CONCLUSIONS
  The levels of AFAFP were higher in the male twins of gender-concordant twins in comparison to female twins. No such difference was found between female versus male fetuses in gender-disconcordant twins.
authors.affiliation: Genetic Institute, Meir Hospital-Sapir Medical Center, Kfar Saba, Israel. sharony@clalit.org.il
authors.forename: Reuven
authors.initials: R
authors.lastname: Sharony
authors.forename: Arie
authors.initials: A
authors.lastname: Drugan
authors.forename: Aliza
authors.initials: A
authors.lastname: Amiel
authors.forename: Julia
authors.initials: J
authors.lastname: Grinshpun-Cohen
authors.forename: Shlomo
authors.initials: S
authors.lastname: Markov
authors.forename: Moshe D
authors.initials: MD
authors.lastname: Fejgin
mesh_terms: D000649:Amniocentesis / Q000379:methods*; D000653:Amniotic Fluid / Q000378:metabolism*; D005260:Female; D016231:Fluorescence Polarization Immunoassay; D006801:Humans; D008297:Male; D011247:Pregnancy; D012727:Sex Characteristics; D014427:Twins / Q000706:statistics & numerical data*; D000509:alpha-Fetoproteins / Q000378:metabolism*
chemical_list: D000509:alpha-Fetoproteins