The dynamics of in vitro maturation of germinal vesicle oocytes

Immature germinal vesicle oocytes recovered from stimulated cycles were spontaneously matured in vitro. Using real-time technology, the dynamics of nuclear maturation were studied and the most favorable duration of MII arrest (i.e., that corresponding with the highest number of matured oocytes displaying a normal activation response) was determined.

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Laura Escrich, Ph.D., Noelia Grau, Ph.D., María José de los Santos, Ph.D., Josep-Lluis Romero, M.D., Antonio Pellicer, M.D., María-José Escribá, Ph.D.

Vol 98, Issue 5, Pages 1147-1151



To evaluate the dynamics of the nuclear maturation (NM) of in vitro-matured (IVM) oocytes and to determine the most favorable duration of meiosis II (MII) arrest in relation to the normal activation response.




University-affiliated infertility clinic.


Donated immature germinal vesicle oocytes (GV).


The GV underwent spontaneous IVM and the dynamics of NM studied by real-time monitoring. IVM oocytes were parthenogenetically activated at different MII arrest points and their response assessed.

Main outcome measure(s):

Moment of GV breakdown; extrusion of the first polar body (1PB); duration of MI and MII arrest; activation rate (AR) and type.


Two GV populations –early (E-IVM: 18.4±2.7hrs) and late (L-IVM: 26.3±3.8hrs; p<0.01) maturing - were defined according to the time required for extrusion of the 1PB. Significantly more E-IVM than L-IVM exhibited a NAR (61.3% vs. 34.6%), but AR were similar (average 88.6%) in both groups. Duration of GV stage differed between the two groups but MI arrest (14.0±0.3hrs) was constant. E-IVM arrested at MII for at least 4.3hrs displayed significantly lower AR and similar NA rates (61.3%) to E-IVM arrested for a shorter time (83.9% vs. 100%). L-IVM displayed a similar AR (80.8%), but lower NA rates than E-IVM (34.6%), regardless of when activation took place. Conclusion(s):

The success of IVM depends on the NM timing rather than on the length of MII arrest.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders. The journal publishes juried original scientific articles in clinical and laboratory research relevant to reproductive endocrinology, urology, andrology, physiology, immunology, genetics, contraception, and menopause. Fertility and Sterility® encourages and supports meaningful basic and clinical research, and facilitates and promotes excellence in professional education, in the field of reproductive medicine.