Association of equine oocyte and cleavage stage embryo morphology with maternal age and pregnancy after intracytoplasmic sperm injection
Bethany L. Frank A B , Courtney D. Doddman C , JoAnne E. Stokes A and Elaine M. Carnevale
A D
+ Author Affiliations
- Author Affiliations
A Equine Reproduction Laboratory, Department of Biomedical Sciences, Colorado State University, 3101 Rampart Road, Fort Collins, CO 80521, USA.
B Sierra Veterinary Specialists & Emergency Center, 555 Morrill Avenue, Reno, NV 89512, USA.
C Equine Veterinary Associates, 1250 Lakeview Avenue, Suite L, Anaheim, CA 92807, USA.
D Corresponding author. Email: elaine.carnevale@colostate.edu
Reproduction, Fertility and Development 31(12) 1812-1822 https://doi.org/10.1071/RD19250
Submitted: 29 June 2019 Accepted: 15 September 2019 Published: 21 October 2019
Abstract
In this retrospective study the morphological characteristics of oocytes and cleavage stage embryos were associated with pregnancy results from clinical intracytoplasmic sperm injection (ICSI) in mares. Oocytes were collected from preovulatory follicles, and images (×200; n = 401) were captured for measurements of ooplasm, the perivitelline space and zona pellucida. After ICSI and before transfer into recipients’ oviducts, cleavage stage embryos were imaged (n = 178). Oocyte donor ages (3–13, 14–19, 20–23, 24–27 years) were compared, as were mares aged 3–13 years without versus with recent histories of performance or injury stress. Cleavage rates did not differ with age. However, pregnancy rates declined and pregnancy loss rates (11–50 days gestation) increased with mare age. Young mares with performance or injury stress had significantly lower pregnancy rates than young mares under management typical for broodmares. No morphological oocyte characteristic was consistently associated with age or pregnancy outcome. Cleavage stage embryo morphology was not associated with pregnancy outcome; however, the rate of embryo development before oviductal embryo transfer was faster (P < 0.05) for embryos that resulted in an early pregnancy (≤17 days) and tended (P ≤ 0.1) to be higher for embryos that produced a 50-day pregnancy. Embryonic vesicles that had a more rapid increase in diameter were more often (P < 0.05) maintained until 50 days gestation.
Additional keywords: blastocyst, ICSI, morula, zygote.
References
Alikani, M., Coheti, J., Tomkin, G., Garrisi, G. J., Mack, C., and Scott, R. T. (1999). Human embryo fragmentation in vitro and its implications for pregnancy and implantation. Fertil. Steril. 71, 836–842.| Human embryo fragmentation in vitro and its implications for pregnancy and implantation.Crossref | GoogleScholarGoogle Scholar | 10231042PubMed |
Altermatt, J. L., Suh, T. K., Stokes, J. E., and Carnevale, E. M. (2009). Effects of age and equine follicle-stimulating hormone (eFSH) on collection and viability of equine oocytes assessed by morphology and developmental competency after intracytoplasmic sperm injection (ICSI). Reprod. Fertil. Dev. 21, 615–623.
| Effects of age and equine follicle-stimulating hormone (eFSH) on collection and viability of equine oocytes assessed by morphology and developmental competency after intracytoplasmic sperm injection (ICSI).Crossref | GoogleScholarGoogle Scholar | 19383268PubMed |
Ball, B. A., Little, T. V., Hillman, R. B., and Woods, G. L. (1986). Pregnancy rates at Days 2 and 14 and estimated embryonic loss rate prior to Day 14 in normal and subfertile mares. Theriogenology 26, 611–619.
| Pregnancy rates at Days 2 and 14 and estimated embryonic loss rate prior to Day 14 in normal and subfertile mares.Crossref | GoogleScholarGoogle Scholar | 16726227PubMed |
Ball, B. A., Little, T. V., Weber, J. A., and Woods, G. L. (1989). Survival of Day 4 embryos from young, normal mares and aged, subfertile mares after transfer to normal recipient mares. J. Reprod. Fertil. 85, 187–194.
| Survival of Day 4 embryos from young, normal mares and aged, subfertile mares after transfer to normal recipient mares.Crossref | GoogleScholarGoogle Scholar | 2915352PubMed |
Bedford, J. M., and Kim, H. H. (1993). Sperm/egg binding patterns and oocyte cytology in retrospective analysis of fertilization failure in vitro. Hum. Reprod. 8, 453–463.
| Sperm/egg binding patterns and oocyte cytology in retrospective analysis of fertilization failure in vitro.Crossref | GoogleScholarGoogle Scholar | 8473467PubMed |
Bertero, A., Ritrovato, F., Evangelista, F., Stabile, V., Fortina, R., Ricci, A., Revelli, A., Vincenti, L., and Nervo, T. (2017). Evaluation of equine oocyte developmental competence using polarized light microscopy. Reproduction 153, 775–784.
| Evaluation of equine oocyte developmental competence using polarized light microscopy.Crossref | GoogleScholarGoogle Scholar | 28283673PubMed |
Borini, A., Lagalla, C., Cattoli, M., Sereni, E., Sciajno, R., Flamigni, C., and Coticchio, G. (2005). Predictive factors for embryo implantation potential. Reprod. Biomed. Online 10, 653–668.
| Predictive factors for embryo implantation potential.Crossref | GoogleScholarGoogle Scholar | 15949227PubMed |
Carnevale, E. M. (2008). The mare model for follicular maturation and reproductive aging in the women. Theriogenology 69, 23–30.
| The mare model for follicular maturation and reproductive aging in the women.Crossref | GoogleScholarGoogle Scholar | 17976712PubMed |
Carnevale, E. M. (2016). Advances in collection, transport and maturation of equine oocytes for assisted reproductive techniques. Vet. Clin. North Am. Equine Pract. 32, 379–399.
| Advances in collection, transport and maturation of equine oocytes for assisted reproductive techniques.Crossref | GoogleScholarGoogle Scholar | 27726987PubMed |
Carnevale, E. M., and Ginther, O. J. (1992). Relationships of age to uterine function and reproduction efficiency in mares. Theriogenology 37, 1101–1115.
| Relationships of age to uterine function and reproduction efficiency in mares.Crossref | GoogleScholarGoogle Scholar | 16727108PubMed |
Carnevale, E. M., and Ginther, O. J. (1995). Defective oocytes as a cause of subfertility in old mares. Biol. Reprod. Mono. 52, 209–214.
| Defective oocytes as a cause of subfertility in old mares.Crossref | GoogleScholarGoogle Scholar |
Carnevale, E. M., and Maclellan, L. J. (2006). Collection, evaluation, and use of oocytes in equine assisted reproduction. Vet. Clin. North Am. Equine Pract. 22, 843–856.
| Collection, evaluation, and use of oocytes in equine assisted reproduction.Crossref | GoogleScholarGoogle Scholar | 17129807PubMed |
Carnevale, E. M., Griffin, P. G., and Ginther, O. J. (1993). Age associated subfertility before entry of embryos into the uterus in mares. Equine Vet. J. 15, 31–35.
Carnevale, E. M., Ramirez, R. J., Squires, E. L., Alvarenga, M. A., Vanderwall, D. K., and McCue, P. M. (2000). Factors affecting pregnancy rates and early embryonic death after equine embryo transfer. Theriogenology 54, 965–979.
| Factors affecting pregnancy rates and early embryonic death after equine embryo transfer.Crossref | GoogleScholarGoogle Scholar | 11097048PubMed |
Choi, Y. H., Love, C. C., Love, L. B., Varner, D. D., Brinsko, S., and Hinrichs, K. (2002). Developmental competence in vivo and in vitro of in vitro matured equine oocytes fertilized by intracytoplasmic sperm injection with fresh or frozen–thawed spermatozoa. Reproduction 123, 455–465.
| Developmental competence in vivo and in vitro of in vitro matured equine oocytes fertilized by intracytoplasmic sperm injection with fresh or frozen–thawed spermatozoa.Crossref | GoogleScholarGoogle Scholar | 11882023PubMed |
Choi, Y. H., Love, L. B., Varner, D. D., and Hinrichs, K. (2004a). Factors affecting developmental competence of equine oocytes after intracytoplasmic sperm injection. Reproduction 127, 187–194.
| Factors affecting developmental competence of equine oocytes after intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 15056784PubMed |
Choi, Y. H., Roasa, L. M., Love, C. C., Varner, D. D., Brinsko, S. P., and Hinrichs, K. (2004b). Blastocyst formation rates in vivo and in vitro of in vitro-matured equine oocytes fertilized by intracytoplasmic sperm injection. Biol. Reprod. 70, 1231–1238.
| Blastocyst formation rates in vivo and in vitro of in vitro-matured equine oocytes fertilized by intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 14695908PubMed |
Ciotti, P. M., Notarangelo, L., Morselli-Labate, A. M., Felletti, V., Porcu, E., and Venturoli, S. (2004). First polar body morphology before ICSI is not related to embryo quality or pregnancy rate. Hum. Reprod. 19, 2334–2339.
| First polar body morphology before ICSI is not related to embryo quality or pregnancy rate.Crossref | GoogleScholarGoogle Scholar | 15347596PubMed |
Cuervo-Arango, J., Claes, A. N., and Stout, T. A. (2019). A retrospective comparison of the efficiency of different assisted reproductive techniques in the horse, emphasizing the impact of maternal age. Theriogenology 132, 36–44.
| A retrospective comparison of the efficiency of different assisted reproductive techniques in the horse, emphasizing the impact of maternal age.Crossref | GoogleScholarGoogle Scholar | 30986613PubMed |
Dandekar, P., Aggeler, J., and Talbot, P. (1992). Structure, distribution and composition of extracellular matrix of human oocytes and cumulus masses. Hum. Reprod. 7, 391–398.
| Structure, distribution and composition of extracellular matrix of human oocytes and cumulus masses.Crossref | GoogleScholarGoogle Scholar | 1375234PubMed |
Dijkstra, A., Cuervo-Arango, J., Stout, T. A. E., and Claes, A. (2019). Monozygotic multiple pregnancies after transfer of single in vitro produced equine embryos. Equine Vet. J , .
| Monozygotic multiple pregnancies after transfer of single in vitro produced equine embryos.Crossref | GoogleScholarGoogle Scholar | 31232484PubMed |
Dunbar, B. S., Avery, S., Lee, V., Prasa, S., Schwahn, D., Schwoebel, E., Skinner, S., and Wilkins, B. (1994). The mammalian zona pellucida: its biochemistry, immunochemistry, molecular biology, and developmental expression. Reprod. Fertil. Dev. 6, 331–347.
| The mammalian zona pellucida: its biochemistry, immunochemistry, molecular biology, and developmental expression.Crossref | GoogleScholarGoogle Scholar | 7831484PubMed |
Ebner, T., Moser, M., Yaman, C., Feichtinger, O., Hartl, J., and Tews, G. (1999). Elective transfer of embryos selected on the basis of first polar body morphology is associated with increased rate of implantation and pregnancy. Fertil. Steril. 72, 599–603.
| Elective transfer of embryos selected on the basis of first polar body morphology is associated with increased rate of implantation and pregnancy.Crossref | GoogleScholarGoogle Scholar | 10521094PubMed |
Ebner, T., Yaman, C., Moser, M., Sommergruber, M., Feichtinger, O., and Tews, G. (2000). Prognostic value of first polar body morphology on fertilization rate and embryo quality in intracytoplasmic sperm injection. Hum. Reprod. 15, 427–430.
| Prognostic value of first polar body morphology on fertilization rate and embryo quality in intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 10655316PubMed |
Gabrielsen, A., Bhatnager, P. R., Petersen, K., and Lindenberg, S. (2000). Influence of zona pellucida thickness of human embryos on clinical pregnancy outcome following in vitro fertilization treatment. J. Assist. Reprod. Genet. 17, 323–328.
| Influence of zona pellucida thickness of human embryos on clinical pregnancy outcome following in vitro fertilization treatment.Crossref | GoogleScholarGoogle Scholar | 11042829PubMed |
Galli, C., Crotti, G., Turini, P., Duchi, R., Mari, G., Zavaglia, G., Duchamp, G., Daels, P., and Lazzari, G. (2002). Frozen thawed embryos produced by ovum pickup of immature oocytes and ICSI are capable to establish pregnancies in the horse. Theriogenology 58, 705–708.
| Frozen thawed embryos produced by ovum pickup of immature oocytes and ICSI are capable to establish pregnancies in the horse.Crossref | GoogleScholarGoogle Scholar |
Galli, C., Colleoni, S., Duchi, R., Lagutina, I., and Lazzari, G. (2007). Developmental competence of equine oocytes and embryos by in vitro procedures ranging from in vitro maturation and ICSI to embryo culture, cryopreservation and somatic cell nuclear transfer. Anim. Reprod. Sci. 98, 39–55.
| Developmental competence of equine oocytes and embryos by in vitro procedures ranging from in vitro maturation and ICSI to embryo culture, cryopreservation and somatic cell nuclear transfer.Crossref | GoogleScholarGoogle Scholar | 17101246PubMed |
Ginther, O. J. (1992). ‘Reproductive Biology of the Mare.’ 2nd edn. (Equiservices: Cross Plains, WI.)
Ginther, O. J., Bergfelt, D. R., Leith, G. S., and Scraba, S. T. (1985). Embryonic loss in mares: incidence and ultrasonic morphology. Theriogenology 24, 73–86.
| Embryonic loss in mares: incidence and ultrasonic morphology.Crossref | GoogleScholarGoogle Scholar | 16726060PubMed |
Grøndahl, M. L., Christiansen, S. L., Kesmodel, U. S., Agerhold, I. E., Lemmen, J. G., Lundstrom, P., Bogstad, J., Raaschou-Jensen, M., and Ladelund, S. (2017). Effect of women’s age on embryo morphology, cleavage rate and competence – a multicenter cohort study. PLoS One 12, e0172456.
| Effect of women’s age on embryo morphology, cleavage rate and competence – a multicenter cohort study.Crossref | GoogleScholarGoogle Scholar | 28422964PubMed |
Hinrichs, K., Choi, Y. H., Walckenaer, B. E., Varner, D. D., and Hartman, D. L. (2007). In vitro produced equine embryos: production of foals after transfer, assessment by differential staining and effect of medium calcium concentrations during culture. Theriogenology 68, 521–529.
| In vitro produced equine embryos: production of foals after transfer, assessment by differential staining and effect of medium calcium concentrations during culture.Crossref | GoogleScholarGoogle Scholar | 17586036PubMed |
Høst, E., Gabrielsen, A., Lindenberg, S., and Smidt-Jensen, S. (2002). Apoptosis in human cumulus cells in relation to zona pellucida thickness variation, maturation stage, and cleavage of the corresponding oocyte after intracytoplasmic sperm injection. Fertil. Steril. 77, 511–515.
| Apoptosis in human cumulus cells in relation to zona pellucida thickness variation, maturation stage, and cleavage of the corresponding oocyte after intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 11872204PubMed |
Kelley, D. E., Gibbons, J. R., Smith, R., Vernon, K. L., Pratt-Phillip, S. E., and Mortensen, C. J. (2011). Exercise affects both ovarian follicular dynamics and hormone concentrations in mares. Theriogenology 76, 615–622.
| Exercise affects both ovarian follicular dynamics and hormone concentrations in mares.Crossref | GoogleScholarGoogle Scholar | 21497892PubMed |
Kölle, S., Sinowatz, F., Boie, G., and Palma, G. (1998). Differential expression of ZPC in the bovine ovary, oocyte and embryo. Mol. Reprod. Dev. 49, 435–443.
| Differential expression of ZPC in the bovine ovary, oocyte and embryo.Crossref | GoogleScholarGoogle Scholar | 9508095PubMed |
Krisher, R. L. (2004). The effect of oocyte quality on development. J. Anim. Sci. 82, E14–E23.
| 15471793PubMed |
Lazarri, G., Crotti, G., Turini, P., Duchi, R., Mari, G., Zavaglia, G., Barbacini, S., and Galli, C. (2002). Equine embryos at the compacted morula and blastocyst stage can be obtained by intracytoplasmic sperm injection (ICSI) of in vitro matured oocytes with frozen–thawed spermatozoa from semen of different fertilities. Theriogenology 58, 709–712.
| Equine embryos at the compacted morula and blastocyst stage can be obtained by intracytoplasmic sperm injection (ICSI) of in vitro matured oocytes with frozen–thawed spermatozoa from semen of different fertilities.Crossref | GoogleScholarGoogle Scholar |
Li, X., Morris, L. H. A., and Allen, W. R. (2001). Influence of co-culture during maturation on the developmental potential of equine oocytes fertilized by intracytoplasmic sperm injection (ICSI). Reproduction 121, 925–932.
| Influence of co-culture during maturation on the developmental potential of equine oocytes fertilized by intracytoplasmic sperm injection (ICSI).Crossref | GoogleScholarGoogle Scholar | 11373179PubMed |
Loutradis, D., Drakakis, P., Kallianidis, K., Milingos, S., Dendrinos, S., and Michalas, S. (1999). Oocyte morphology correlates with embryo quality and pregnancy rate after intracytoplasmic sperm injection. Fertil. Steril. 72, 240–244.
| Oocyte morphology correlates with embryo quality and pregnancy rate after intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 10438988PubMed |
Maher, J. M., Squires, E. L., Voss, J. L., and Shideler, R. K. (1983). Effect of anabolic steroids on reproductive function of young mares. J. Am. Vet. Med. Assoc. 183, 519–524.
| 6413467PubMed |
McDowell, K. L., Powell, D. G., and Baker, C. B. (1992). Effect of book size and age of mare and stallion on foaling rates in thoroughbred horses. J. Equine Vet. Sci. 12, 364–367.
| Effect of book size and age of mare and stallion on foaling rates in thoroughbred horses.Crossref | GoogleScholarGoogle Scholar |
McKinnon, A. O., and Squires, E. L. (1988). Morphologic assessment of the equine embryo. J. Am. Vet. Med. Assoc. 192, 401–406.
| 3281922PubMed |
Mortensen, C. J., Choi, Y. H., Hinrichs, K., Ing, N. H., Kraemer, D. C., Vogelsang, S. G., and Vogelsang, M. M. (2009). Embryo recovery from exercised mares. Anim. Reprod. Sci. 110, 237–244.
| Embryo recovery from exercised mares.Crossref | GoogleScholarGoogle Scholar | 18295989PubMed |
Navarro, P. A., Medeiros de Araujo, M., Medeiros de Araujo, C., Rocha, M., dos Reis, R., and Martins, W. (2009). Relationship between first polar body morphology before intracytoplasmic sperm injection and fertilization rate, cleavage rate and embryo quality. Int. J. Gynaecol. Obstet. 104, 226–229.
| Relationship between first polar body morphology before intracytoplasmic sperm injection and fertilization rate, cleavage rate and embryo quality.Crossref | GoogleScholarGoogle Scholar | 19105998PubMed |
Otsuki, J., Okada, A., Morimoto, K., Nagai, Y., and Kubo, H. (2004). The relationship between pregnancy outcome and smooth endoplasmic reticulum clusters in MII human oocytes. Hum. Reprod. 19, 1591–1597.
| The relationship between pregnancy outcome and smooth endoplasmic reticulum clusters in MII human oocytes.Crossref | GoogleScholarGoogle Scholar | 15180981PubMed |
Roberts, M. A., London, K., Campos-Chillon, L. F., and Altermatt, J. L. (2015). Presumed monozygotic twins develop following transfer of an in vitro-produced equine embryo. J. Equine Sci. 26, 89–94.
| Presumed monozygotic twins develop following transfer of an in vitro-produced equine embryo.Crossref | GoogleScholarGoogle Scholar | 26435682PubMed |
Sakkas, D., Percival, G., D’Arcy, Y., Sharif, K., and Afnan, M. (2001). Assessment of early cleaving in vitro fertilized human embryos at the 2-cell stage before transfer improves embryo selection. Fertil. Steril. 76, 1150–1156.
| Assessment of early cleaving in vitro fertilized human embryos at the 2-cell stage before transfer improves embryo selection.Crossref | GoogleScholarGoogle Scholar | 11730743PubMed |
Serhal, P. F., Ranieri, D. M., Kinis, A., Marchant, S., Davies, M., and Khadum, I. M. (1997). Oocyte morphology predicts outcome of intracytoplasmic sperm injection. Hum. Reprod. 12, 1267–1270.
| Oocyte morphology predicts outcome of intracytoplasmic sperm injection.Crossref | GoogleScholarGoogle Scholar | 9222015PubMed |
Shoukir, Y., Chardonnens, D., Campan, A., Bischof, P., and Sakkas, D. (1998). The rate of development and time of transfer play different roles in influencing the viability of human blastocysts. Hum. Reprod. 13, 676–681.
| The rate of development and time of transfer play different roles in influencing the viability of human blastocysts.Crossref | GoogleScholarGoogle Scholar | 9572433PubMed |
Somfai, T., Inaba, Y., Aikawa, Y., Ohtake, M., Kobayashi, S., Konishi, K., and Imai, K. (2009). Relationship between the length of cell cycles, cleavage pattern, and developmental competence during in vitro culture of in vitro-matured/in vitro-fertilized bovine oocytes. Reprod. Fertil. Dev. 21, 209–210.
| Relationship between the length of cell cycles, cleavage pattern, and developmental competence during in vitro culture of in vitro-matured/in vitro-fertilized bovine oocytes.Crossref | GoogleScholarGoogle Scholar |
Squires, E. L., Voss, J. L., and Maher, J. M. Squires, E. L., Voss, J. L., and Maher, J. M. (1985). Fertility of young mares after long-term anabolic steroid treatment. J. Am. Vet. Med. Assoc. 186, 583–587.
| 3988591PubMed |
Sun, Y. P., Xu, Y., Cao, T., Su, Y. C., and Guo, Y. H. (2005). Zona pellucida thickness and clinical pregnancy outcome following in vitro fertilization. Int. J. Gynaecol. Obstet. 89, 258–262.
| Zona pellucida thickness and clinical pregnancy outcome following in vitro fertilization.Crossref | GoogleScholarGoogle Scholar | 15919392PubMed |
Suppinyopong, S., Choavaratana, R., and Karavakul, C. (2000). Correlation of oocyte morphology with fertilization rate and embryo quality after intracytoplasmic sperm injection. J. Med. Assoc. Thai. 83, 627–632.
| 10932488PubMed |
Talbert, G. B. (1968). Effect of maternal age on reproductive capacity. Am. J. Obstet. Gynecol. 102, 451–477.
| Effect of maternal age on reproductive capacity.Crossref | GoogleScholarGoogle Scholar | 4877579PubMed |
Tremoleda, J. L., Stout, T. A. E., Lagutina, I., Lazzari, G., Bevers, M. M., Colebrander, B., and Galli, C. (2003). Effects of in vitro production on horse embryo morphology, cytoskeletal characteristics, and blastocyst capsule formation. Biol. Reprod. 69, 1895–1906.
| Effects of in vitro production on horse embryo morphology, cytoskeletal characteristics, and blastocyst capsule formation.Crossref | GoogleScholarGoogle Scholar | 12904313PubMed |
Vanderwall, D. K. (1996). Early embryonic development and evaluation of equine embryo viability. Vet. Clin. North Am. Equine Pract. 12, 61–83.
| 8726450PubMed |
Vanderwall, D. K. (2008). Early embryonic loss in the mare. Equine Vet. J. 28, 691–702.
| Early embryonic loss in the mare.Crossref | GoogleScholarGoogle Scholar |
Vanderwall, D. K., Peyrot, L. M., Weber, J. A., and Woods, G. L. (1989). Reproductive efficiency of the aged mare. In ‘Proceedings of the Annual Meeting Society of Theriogenology’, 29–30 Sep 1989, Coeur d’Alene, ID. pp. 153–156. (American Society for Theriogenology: Pike Road, AL)
Villahoz, M. D., Squires, E. L., Voss, J. L., and Shideler, R. K. (1985). Some observations on early embryonic death in mares. Theriogenology 23, 915–924.
| Some observations on early embryonic death in mares.Crossref | GoogleScholarGoogle Scholar |
Werner, M. A., Barnhard, J., and Gordon, J. W. (1991). The effects of aging on sperm and oocytes. Semin. Reprod. Endocrinol. 9, 231–240.
| The effects of aging on sperm and oocytes.Crossref | GoogleScholarGoogle Scholar |
Xia, P. (1997). Intracytoplasmic sperm injection: correlation of oocyte grade based on polar body, perivitelline space and cytoplasmic inclusions with fertilization rate and embryo quality. Hum. Reprod. 12, 1750–1755.
| Intracytoplasmic sperm injection: correlation of oocyte grade based on polar body, perivitelline space and cytoplasmic inclusions with fertilization rate and embryo quality.Crossref | GoogleScholarGoogle Scholar | 9308806PubMed |
Younis, J. S., Radin, O., Mirsky, N., Izhaki, I., Majara, T., Bar-ami, S., and Ben-ami, M. (2008). First polar body and nucleolar precursor body morphology is related to the ovarian reserve of infertile women. Reprod. Biomed. Online 16, 851–858.
| First polar body and nucleolar precursor body morphology is related to the ovarian reserve of infertile women.Crossref | GoogleScholarGoogle Scholar | 18549696PubMed |
