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.


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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