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post-fertilisation and that implants into the endometrium ), blastocyst euploidy rates ( the proportion of blastocysts with a normal chromosome make-up ) and pregnancy rates per euploid blastocyst . Since oocyte quality is the pivotal determinant of virtually all these key performance indicators , and varies inversely with female age , the latter is of overarching importance . Put simply , older women need to freeze more oocytes than younger women to achieve the same outcome .
One study provided an objective estimate of age-specific numbers of oocytes required to be frozen based on modelling that incorporated these variables . 7 Using an extensive dataset , this model incorporated a 95 % post-thaw oocyte survival rate for women aged under 36 and an 85 % survival for those aged ≥36 , as well as ~ 70 % fertilisation rate , age-specific blastocyst formation and euploidy rates , and an ~ 60 % live birth rate per euploid blastocyst . 7
They found that women aged 34 , 37 and 42 would need to freeze 10 , 20 and 61 mature oocytes , respectively , to have a 75 % chance of having at least one live birth . In other words , because of the unrelenting decline in the proportion of good-quality oocytes with age , 42-year-olds need to freeze six times as many oocytes to achieve comparable outcomes to 34-year-olds .
Similarly , women at 34 , 37 and 42 , each with 20 frozen oocytes , were estimated to have a 90 %, 75 % and 37 % likelihood of having at least one live birth and a 66 %, 39 % and 7 % likelihood of two live births , respectively . It is important to note that the oocyte survival rates reported for this study ( 85-95 %) were very good and that prospects would be lower for clinics with lower thaw survival rates .
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Accessing egg freezing
The starting point for undertaking an
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oocyte cryopreservation cycle typically involves a GP referral to a fertility specialist . Some IVF companies also facilitate direct referral pathways from hospitals for urgent cancer-related cases . Prior to an oocyte cryopreservation cycle , patients typically undertake screening for HIV , hepatitis B / C , syphilis , chlamydia and gonorrhoea . Since oocyte retrieval is undertaken as a day-case procedure , patients should be medically fit and have a BMI of less than 35 .
For patients with a BMI of 35 or greater , or those with more complex medical conditions , some of the larger IVF clinics have the
facility for undertaking oocyte retrievals in hospitals with more extensive support services and inpatient stays . There is evidence that obesity adversely impacts oocyte quality , so weight loss prior to oocyte cryopreservation may confer additional benefits apart from procedural safety .
An AMH level is informative as this provides insight into likely oocyte yield and a guide for FSH dosing . 6 Long-term use of combined oral contraceptives inhibits follicle development beyond the pre-antral stage and can thus lower antral follicle count and AMH levels and compromise oocyte return . It is therefore advisable that patients discontinue pill usage for at least one month prior to undergoing an oocyte cryopreservation cycle to optimise oocyte output .
Currently , it is uncertain that interventions aimed at oocyte rejuvenation can markedly improve oocyte quality . 2 As a result , pre-treatment with antioxidants , such as coenzyme Q10 , is not generally
warranted . If such agents are used , however , it should be for at least 1-2 months prior to oocyte cryopreservation since the quality of oocytes in a given menstrual cycle is largely defined during the preceding 2-3 months while they are undergoing their growth phase . 2
Cost
Billing for IVF cycles is complex , involving multiple MBS item numbers and often multiple providers , including the fertility specialist , fertility company , day hospital and anaesthetist . The out-of-pocket cost of an
Local knowledge of oocyte cryopreservation and its efficacy remains limited as relatively few women have returned to thaw oocytes .
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oocyte cryopreservation cycle depends on whether it is deemed to be medically indicated ( conferring eligibility for Medicare rebates ) and whether the patient has private health cover .
Medical indications , such as cancerrelated fertility preservation , attract Medicare rebates amounting to around 40-50 % of the total cycle cost , the value of which can vary from one clinic to the next .
Endometriosis involving the ovaries (‘ chocolate cysts ’ or endometriomas ) may be considered another medical indication for fertility preservation as , when severe , it threatens the ovarian follicular reserve and distorts pelvic architecture . Given the almost inevitable loss of normal ovarian tissue with surgical excision of endometriomas and lower oocyte yields post-cystectomy , it is increasingly recommended that oocyte cryopreservation be performed preoperatively . 8 , 9
Private health funds predominantly contribute to in-hospital treatment costs , which
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in the case of oocyte cryopreservation , involves the oocyte retrieval procedure . For Medicare eligible cycles , medication-related costs amount to the co-payments for prescriptions , with blood test and ultrasound scan costs covered under a global cycle fee . There is also an annual fee for maintaining oocytes that is set by the different IVF companies . More detailed information regarding costs is readily available from individual IVF clinics .
The current role of egg freezing
Oocyte cryopreservation can be a highly
effective form of fertility preservation , conferring potentially high chances of pregnancy in later reproductive years , especially if performed when oocyte quality ( and numbers ) are highest . In practice , this means in women aged under 37 .
A recent cost-analysis study found that , if a 43-year-old woman used her oocytes that were previously frozen at age 33 , it would be considerably more cost-effective and more likely to result in a live birth compared with undergoing a fresh IVF cycle with chromosomal embryo testing at her current age . 10
Nevertheless , local knowledge of oocyte cryopreservation and its efficacy remains limited as relatively few women have returned to thaw oocytes ; the ratio of thaw cycles to oocyte cryopreservation cycles from 2010 to 2015 in Australia was only 14 %. 1 Continuing to monitor outcomes of thawed oocytes will be important for informing the utility of this rapidly growing technology , which at present , is the most viable option for combating the inevitable effects of ageing , as well as the gonadotoxic effects of conditions like endometriosis and cancer and their treatments .
References on request from kate . kelso @ adg . com . au
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Sperm banking via freezing has been in use for decades , whereas effective oocyte cryopreservation is more challenging . |