The influence of zygote pronuclear morphology on in vitro human embryo development

  • Lidija Križančić-Bombek
  • Veljko Vlaisavljević
Keywords: assisted reproduction, pronuclear morphology, nucleolar precursor bodies, embryo morphology, blastocyst morphology


Background: The selection of embryos with largest implantation potential is an important part in assisted reproduction. Besides the embryo or blastocyst morphology, selection criteria such as position and orientation of pronuclei (PN) in relation to polar body positioning and the number, size and distribution of nucleolar precursor bodies (NPB) have been proposed. In our study, a correlation between PN and NBP morphology with the development of early embryos (day 2 of cultivation) and blastocysts (day 5) was investigated.

Methods: 653 zygotes from 113 IVF (in vitro fertilization) and ICSI (intracytoplasmic sperm injection) patients, younger than 40 years, were assessed 18–20 hours post-insemination. Optimal zygotes (Z1) had thouching centrally located PN with equall numbers of alligned NPB. Other zygote types differred from Z1 in having scattered NPB in both PN (Z2) or alligned NPB in one PN (Z3) or in PN beeing distant from one another (Z4). For each zygote type a percentage of normal early embryos and blastocysts was calculated.

Results: Among 653 assessed zygotes 21.8 % were Z1; 29.1 % Z2, 34.6 % Z3 and 14.5 % Z4. The percentage of normal early embryos decreased from Z1 to Z4 zygote type (70.4 % vs. 55.3 % vs. 59.7 % vs.45.3 %; p < 0.05) as well as the percentage of developed blastocysts (63.4 % vs. 55.3 % vs. 58.8 % vs. 43.2 %). However, the percentages of optimal blastocysts in the four groups did not differ (11.3 % vs. 11.1 % vs. 8.4 % vs. 6.3 %).

Conclusions: Best grade zygotes result in batter early embryo and blastocyst development suggesting that zygote morphology can be used in combination with embryo and/or blastocyst evaluation as a method for embryo selection prior to embryo transfer.


Download data is not yet available.


Scott L. The biological basis of non-invasive strategies for selection of human oocytes and embryos. Hum Reprod Update 2003; 9: 237–49.

Vlaisavljević V, Kovačič B, Gavrić-Lovrec V, Reljič M, Petrovič V, Čižek-Sajko M, Kovač V. Vpliv izbire zarodkov, spočetih z vnosom semenčice v citoplazmo jajčne celice, na vgnezditev zarodkov po prenosu v maternico. Zdrav Vestn 2002; 71 Suppl. 1: 7–11.

Kovacic B, Vlaisavljevic V, Reljic M, Cizek-Sajko M. Developmental capacity of different morphological types of day 5 human morulae and blastocysts. RBM Online 2004; 8: 687–94.

Balaban B, Urman B, Isiklar A, Alatas C, Aksoy S, Mercan R, et al. The effect of pronuclear morphology on embryo quality parameters and blastocyst transfer outcome. Hum Reprod 2001; 16: 2357–61.

Wharf E, Dimitrakopoulos A, Khalaf Y, Pickering S. Early embryo development is an indicator of implantation potential. RBM Online 2004; 8: 212–8.

Lundqvist M, Johansson U, Lundkvist Ö, Milton K, Westin C, Simberg N. Does pronuclear morphology and/or early cleavage rate predict embryo implantation potential? RBM Online 2001; 2: 12–6.

Kattera S, Chen C. Developmental potential of human pronuclear zygotes in relation to their pronuclear orientation. Hum Reprod 2004; 19: 294–9.

Ginaroli L, Magli MC, Ferraretti AP, Fortini D, Grieco N. Pronuclear morphology and chromosomal abnormalities as scoring criteria for embryo selection. Fertil Steril 2003; 80: 341–9.

Ginaroli L, Magli MC, Ferraretti AP, Lapi M, Borghi E, Ermini B. Oocyte euploidy, pronuclear zygote morphology and embryo chromosomal complement. Hum Reprod 2007; 22: 241–9.

Scott, L. Pronuclear scoring as a predictor of embryo development. RBM Online 2003; 6: 201–14.

Tesarik J, Junca AM, Hazout A, Aubriot FX, Nathan C, Cohen- Bacrie P, Dumont-Hassan M. Embryos with high implantation potential after intracytoplasmic sperm injection can be recognized by a simple, non-invasive examination of pronuclear morphology. Hum Reprod 2000; 15: 1396–9.

Tesarik J, Greco E. The probability of abnormal preimplantation development can be predicted by a single static observation on pronuclear stage morphology. Hum Reprod 1999; 14: 1318–23.

Nagy ZP, Dozortsev D, Diamond M, Rienzi L, Ubaldi F, Abdelmassih R, Greco E. Pronuclear morphology evaluation with subsequent evaluation of morphology significantly increases implantation rates. Fertil Steril 2003; 80: 67–74.

Scott L, Alvero R, Leondires M, Miller B. The morphology of human pronuclear embryos is positively related to blastocyst development and implantation. Hum Reprod 2000; 15: 2394–403.

Vlaisavljević V, Kovačič B. Naše prve izkušnje s tehniko direktnega vnosa semenčice v citoplazmo jajčne celice pri zdravljenju moške neplodnosti. Zdrav Vestn 1995; 64: 677–9.

Balaban B, Yakin K, Urman B, Isiklar A, Tesarik J. Pronuclear morphology predicts embryo development and chromosome constitution. RBM Online 2004; 8: 695–700.

Tesarik J, Kopecny V. Development of human male pronucleus: ultrastructure and timing. Gamete Research 1989; 24: 135–49.

Sjöblom P, Menezes J, Cummins L, Mathiyalagan B, Costello MF. Prediction of embryo developmental potential and pregnancy based on early stage morphological characteristics. Fertil Steril 2006; 86: 848–61.

How to Cite
Križančić-Bombek L, Vlaisavljević V. The influence of zygote pronuclear morphology on in vitro human embryo development. ZdravVestn [Internet]. 1 [cited 19Oct.2019];76(9). Available from:
Professional article

Most read articles by the same author(s)

1 2 > >>