Can You Ever Collect Too Many Oocytes?
Can You Ever Collect Too Many Oocytes?
The number of oocytes collected varied from 1 to 48. CP rate per embryo transfer varied from 10.2% when only one oocyte was collected to 37.7% when >16 oocytes were collected. LB rate per embryo transfer varied from 9.2% following collection of 1 oocyte to 31.3% following collection of >16 oocytes. The rates of both of these outcomes increased as the number of oocytes collected increased but there was considerable scatter about the trend both for all the cycles (Fig. 1) and for first oocyte collections (Table I). The effects of age and blastocyst transfer are shown in Figs 2 and 3. In this data set stimulation protocol and BMI had no significant association with CP or LB rates and are not reported separately.
(Enlarge Image)
Figure 1.
Clinical pregnancy (CP) and live birth (LB) rates with respect to number of oocytes collected (results with over 20 oocytes are grouped (18–19, 20–21, 22–23, 24–27, >28) because of small numbers). Error bars are 95% confidence limits.
(Enlarge Image)
Figure 2.
Clinical pregnancy (CP) and live birth (LB) rates with respect to number of oocytes collected by age groups (results with under 2 and over 19 oocytes have been grouped because of small numbers).
(Enlarge Image)
Figure 3.
Outcome with respect to stage of transfer groups (results with over 19 oocytes for the blastocyst group and over 13 oocytes for the cleavage group have been grouped because of small numbers).
To allow for the other factors, which affect pregnancy rates, logistic regression analysis was performed on the results for women having their first oocyte collection. There was no evidence of a decline in the CP or LB rates with oocyte number, there being weakly significant (P < 0.05) upward trends with log oocyte number (Table II). There were no significant interactions between age and oocyte number or blastocyst transfer and oocyte number on the outcomes. Table III shows the effects of age group and blastocyst transfer on CP and LB. The upward trend CP and LB with oocyte number is only clear in the 30- to 34-year age group.
When all 7697 cycles were analysed by GEE, oocyte collection number and previous ART birth were also significantly related to pregnancy rates and there was a more significant increase in both CP and LB with log oocyte number (Table IV). There were no significant interactions between age and oocyte number or blastocyst transfer and oocyte number on the outcomes.
We also examined the relationship between oocyte immaturity and number of oocytes collected in those patients who had ICSI and confirmed a significant upward trend (P < 0.001) to ~22% in those with >16 oocytes collected (Table V).
The proportion of women with embryos cryopreserved and the average numbers of embryos frozen increased markedly with the number of oocytes collected. Patients aged <45 using their own frozen embryos in the same time (August 2010 and July 2012) had 1658 clinical pregnancies (31% per transfer) and 1299 births (24% per transfer). The birth rate per thawed embryo was 18% (1299/7257). These figures were used to calculate the potential number of extra births from use of frozen embryos in Table V.
The 44 patients who had embryo cryopreservation and no fresh embryo transfer in the time of the study had 10–53, mean 26 oocytes collected and 257 mean 5.8 embryos frozen. While these 'freeze all' treatments were only 0.6% of the total they were 1.2% of those with 10 or more oocytes collected (Table V) and the frequency of freeze all increased with the number of oocytes collected (>16, 2.6%, >20, 3.0%, >24 6.7%, >28 11.7%).
Results
The number of oocytes collected varied from 1 to 48. CP rate per embryo transfer varied from 10.2% when only one oocyte was collected to 37.7% when >16 oocytes were collected. LB rate per embryo transfer varied from 9.2% following collection of 1 oocyte to 31.3% following collection of >16 oocytes. The rates of both of these outcomes increased as the number of oocytes collected increased but there was considerable scatter about the trend both for all the cycles (Fig. 1) and for first oocyte collections (Table I). The effects of age and blastocyst transfer are shown in Figs 2 and 3. In this data set stimulation protocol and BMI had no significant association with CP or LB rates and are not reported separately.
(Enlarge Image)
Figure 1.
Clinical pregnancy (CP) and live birth (LB) rates with respect to number of oocytes collected (results with over 20 oocytes are grouped (18–19, 20–21, 22–23, 24–27, >28) because of small numbers). Error bars are 95% confidence limits.
(Enlarge Image)
Figure 2.
Clinical pregnancy (CP) and live birth (LB) rates with respect to number of oocytes collected by age groups (results with under 2 and over 19 oocytes have been grouped because of small numbers).
(Enlarge Image)
Figure 3.
Outcome with respect to stage of transfer groups (results with over 19 oocytes for the blastocyst group and over 13 oocytes for the cleavage group have been grouped because of small numbers).
To allow for the other factors, which affect pregnancy rates, logistic regression analysis was performed on the results for women having their first oocyte collection. There was no evidence of a decline in the CP or LB rates with oocyte number, there being weakly significant (P < 0.05) upward trends with log oocyte number (Table II). There were no significant interactions between age and oocyte number or blastocyst transfer and oocyte number on the outcomes. Table III shows the effects of age group and blastocyst transfer on CP and LB. The upward trend CP and LB with oocyte number is only clear in the 30- to 34-year age group.
When all 7697 cycles were analysed by GEE, oocyte collection number and previous ART birth were also significantly related to pregnancy rates and there was a more significant increase in both CP and LB with log oocyte number (Table IV). There were no significant interactions between age and oocyte number or blastocyst transfer and oocyte number on the outcomes.
We also examined the relationship between oocyte immaturity and number of oocytes collected in those patients who had ICSI and confirmed a significant upward trend (P < 0.001) to ~22% in those with >16 oocytes collected (Table V).
The proportion of women with embryos cryopreserved and the average numbers of embryos frozen increased markedly with the number of oocytes collected. Patients aged <45 using their own frozen embryos in the same time (August 2010 and July 2012) had 1658 clinical pregnancies (31% per transfer) and 1299 births (24% per transfer). The birth rate per thawed embryo was 18% (1299/7257). These figures were used to calculate the potential number of extra births from use of frozen embryos in Table V.
The 44 patients who had embryo cryopreservation and no fresh embryo transfer in the time of the study had 10–53, mean 26 oocytes collected and 257 mean 5.8 embryos frozen. While these 'freeze all' treatments were only 0.6% of the total they were 1.2% of those with 10 or more oocytes collected (Table V) and the frequency of freeze all increased with the number of oocytes collected (>16, 2.6%, >20, 3.0%, >24 6.7%, >28 11.7%).
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