The effect of pronuclear morphology on early development and chromosomal abnormalities in cleavage-stage embryos.
BACKGROUND
Pronuclear (PN) zygote morphology has been proposed as a useful tool for selecting the best embryos for transfer.


METHODS
PN morphology was recorded in 888 zygotes and classified according to similar/different PN size [groups A (n = 816) and B (n = 72)] and to the number, distribution and synchrony of nucleolar precursor bodies (NPB): subgroup I, pronuclei with 3-4 polarized NPB; subgroup II, 5-7 synchronic polarized NPB or 7-10 NPB distributed randomly; and subgroup III, morphologies other than those of groups I or II. Embryo development and chromosomal abnormalities were evaluated for each PN pattern.


RESULTS
In patients aged </=37 years, the number of zygotes reaching morula and blastocyst stage was significantly (P = 0.0003) higher in group A than in group B. In group A, the incidence of chromosomal abnormalities was significantly (P = 0.0247) lower than in group B, and significant differences were observed when pattern AI was compared with pattern AII (P = 0.0280), AIII (P = 0.0024), BIII (P = 0.0077) and total B (P = 0.0247). In patients aged >37 years, statistical differences among groups were not observed.


CONCLUSIONS
In patients aged </=37 years, zygotes with similar PN size and with polarized NPB present the best prognosis based on embryo development and the incidence of chromosomal abnormalities, whereas in patients aged >37 years, this correlation does not exist.
Instituto Valenciano de Infertilidad (IVI), Plaza Policía Local, Valencia, Spain.
Pilar
P
Gámiz
Carmen
C
Rubio
M José
MJ
de los Santos
Amparo
A
Mercader
Carlos
C
Simón
José
J
Remohí
Antonio
A
Pellicer
D000328:Adult; D001755:Blastocyst; D002869:Chromosome Aberrations / Q000196:embryology* / Q000706:statistics & numerical data; D002970:Cleavage Stage, Ovum; D004622:Embryo, Mammalian / Q000502:physiology*; D005314:Embryonic and Fetal Development; D005260:Female; D006801:Humans; D009028:Morula; D011379:Prognosis; D015053:Zygote / Q000648:ultrastructure*