This post was updated on July 14th, 2019

The egg freezing solution to age related fertility decline

After having just spent a ridiculous amount of effort putting together the best article you will ever read about age-related fertility decline (if I do say so myself☺) I realized it was incumbent on me to follow up with some solid solutions rather than just a presentation of the problem.

So let’s talk egg freezing.

Facebook and Apple make the news again (for egg freezing?!)

Freezing eggs, or “oocyte cryopreservation” as it’s known amongst the reproductive medicine crowd has gotten to be one of the most hotly discussed topics right now in the fertility field since the invention of IVF.

In case you missed the mass media bubble that formed in October 2014 when Facebook and Apple announced they were offering egg freezing benefits to female employees, what I’m talking about here is the harvesting of your eggs (aka oocycte, or ovum) and putting them in the deep-freeze so they can be used in the event that you become infertile in the intervening years due to your eggs getting too old.

Should you consider freezing your eggs?

The Annoying “Depends” Answer

This sounded pretty smart to me when I first heard about it. But like most open-minded women, I’ve been around long enough now to know not to jump to conclusions about what is “right” and “wrong” as the answer almost always “depends” doesn’t it?

Knowing what is medically possible is just the first step. Questions concerning efficacy, alternative methods, ethics and cost then provide the context into which individuals can consider what is “right” for them, and clearly many are making the decision to undergo this fertility preserving process so there must be something to it in my mind.

The gist of this post on freezing eggs

Having now dedicated myself to learning as much as I can about how to freeze eggs and why, which includes a recent interview with leading fertility specialist Dr Kee Ong, I’ve decided to give you an overview of this topic because I figure there must be more than a few of you  wanting to know more about this fantastic technology. As well as a general overview, in this article I will give you:

• an easy-to-follow description of egg freezing technology – what to expect and details on how to freeze eggs (there are a couple of different methods)
• a view into the kinds of women electing to freeze eggs
• an update on the efficacy and latest medical opinions on egg freezing, and

A whole lot of other interesting stuff you didn’t realize you wanted to know ☺

My goal here, as always, is to provide you with an unbiased, reliable and comprehensive package of knowledge so that you will be more informed when making your fertility choices.

So shall we get started?

What to expect if you decide on freezing your eggs

If you decide to sign up and freeze some of those tincey wincey eggs of yours (or opt for oocyte cryopreservation as its formally known) this is what would happen at the fertility clinic, physically speaking. I will be writing a much more in-depth post on the process soon for all of you who want the nitty gritty details but for now here is a general overview of the process.

1. After all your pre-start checks (including a blood test for how many eggs you have left – the AMH test), you would start your egg retrieval using one of the three protocols that are commonly used in IVF.

This would essentially entail jabbing yourself with follicle stimulating hormone (FSH) for between 7 – 12 days until one of the fat-rolls in your tummy looks like the arm of a heroin junky – just kidding, it’s not that bad. Well not quite that bad.. The needle is short and super-duper thin so it hardly hurts at all (unless you’re a big wimp like me and then it hurts a bit, especially if there is someone around that you can complain to).

You may also be required to take some additional shots to stop you from ovulating too soon so you’ll get pretty good at stabbing yourself before too long.

2. After the FSH has swollen you ovaries to the size of a decent serving of grapes, you will be given a “trigger shot” of the drug HCG to release the grapes (I-mean-eggs) enabling your fertility specialist to “go in” the following day and clean-up with a specially designed vacuum cleaner.

Ideally, you’ll get about 8 – 15 eggs during this step, but depending on your personal diagnosis (and the subsequent method used), far fewer, or many more may be collected.

When I did my first IVF cycle, I ovulated 44 eggs which while a record for the clinic, was NOT a good result by any stretch of the imagination. I was super sick, and most of the eggs were too under-developed to be used so it’s not just a matter of getting a good number of eggs, the doctors are also trying to optimize the numbers that are mature when they select the appropriate dose of FSH for you.

Also if you have PCOS like me you will need a much lower dose and need to be monitored closely to make sure you are not overstimulated like I ended up being.

3. It’s at this point during IVF, where the party in a petrie-dish normally occurs, women interested in egg freezing, instead send their little girls to the deep freezer to wait for party-time at a later date.

4. Lab technicians take your unfertilized eggs, treat them with a chemical to stop them getting freezer-burn, then quickly snap-freeze them down to -320 ºF (-196 ºC). At this temperature all biochemical reactions cease meaning your eggs stay nice and fresh until you’re ready for them!

5. In the meantime, you head home, and take the rest of the day off. You’ll need it. It may take a few days for your psyched up ovaries to shrink back down to a normal size, and depending on how sensitive you are to changes in hormone levels, you may experience some discomfort as a side-effect until they do.

That’s it. You’re now officially an “egg freezer” with your own little safe-deposit box at the lab, which you’ll pay an annual fee for, to keep, until you want to start making withdrawals.

So why do women choose to freeze eggs?

What “sort” of people are choosing to freeze their eggs these days?

Well, the first baby born from a frozen (then thawed egg) was reported in 1986 (Lassalle et. al 1986) but it wasn’t until the early 2000’s that improvements in both freezing techniques (and the subsequent IVF treatment needed to use those frozen eggs) was at a sufficient level to enable the practice to become a commercially available, whilst still experimental, option.

Oncologic Egg Freezers

Egg freezing has enabled women under-going cancer or organ transplants to hang on to the hope of a having a family one day.  Ordinarily, chemotherapy and radiation prematurely ends the ovaries working life, so for young girls in particular, choosing to freeze eggs prior to their life saving therapy seems like a great option if you ask me.

Social Egg Freezers Give The Thumbs Up to Others

A study published in 2015 concluded that the majority of women who choose to freeze eggs in the absence of presenting medical conditions do so because they are single and are hoping to buy time in their search for a suitable partner (Stoop et. al 2015).

I found this study interesting because much of the big hubbub with Facebook, Apple and the many other companies offering egg freezing to employees was the resentment towards companies pressuring women to delay childbearing for career reasons. Well, as it turns out – most women just haven’t met “Mr Right” yet!

This study was performed on a group of women with a mean age of 37, who were all considering freezing eggs to combat age-related fertility decline.

Despite the differing views of these women during a follow-up survey 12 – 45 months later, almost all of the participants would recommend the treatment to others. It was suggested that this finding provides insight into the important psychological aspects of reassurance associated with egg banking.

Egg freezing does not impact women’s commitment to existing partners

Most interestingly however, no differences were observed in the stability of partner relations between those that chose to bank their eggs verses those that did not. This counters the argument proposed by some social commentators that egg banking affects the decision of women when it comes to deciding to continue a relationship with their existing partners if they are given more time.

How to freeze eggs – the types of egg freezing

Whatever other information you’re reading on egg freezing at the moment, make sure you understand the two types of methods for freezing eggs, as the differences in performance may have an impact on whether you think this technology is right for you or not.

The short answer is that “slow freezing” is the older way of doing it, while “vitrification” is the newer egg freezing method. While some clinics have reported equivalent, good success rates with both methods (Grifo and Noyes 2010), vitrification has out-performed slow freezing in clinical trials as shown in Table 1 below.

While in the past there was contradicting opinions in the published literature regarding the limitations and potential benefits of these techniques, as of 2015, there seems to be a general consensus in the scientific community that vitrification is the better of the two methods.

Most IVF centers nowadays have adopted vitrification as the method of choice for cryopreserving their client’s eggs, but you need to check with your clinic, as slow freezing is still out there in some clinics.

Vitrification vs. Slow Freezing Success Rates

Table 1.  A summary of randomized controlled trials reporting the egg survival rate of slow freezing and vitrification.

If you care to know more about slow freezing and vitrification technology see the section below, or else you can probably get away with skipping down to Risk and Effectiveness of Egg Freezing if you keep in mind that I’m talking about vitrification from now on.

The methods of how to freeze eggs explained

In both slow-freezing and vitrification around 90% of the water within the egg cells is removed prior to lowering the temperature to avoid ice crystal formation within the cells as ice crystals can damage the cells leading to low survival rates after thawing . This ‘chilling injury’ is similar to what happens to most fruit and vegetables when they are frozen at home and was the key challenge for earlier egg freezing pioneers.

The ‘bruised fruit’ phenomenon has been overcome through the use of cryoprotectants prior to freezing, which are essentially “anti-freeze” chemicals that are substituted with the water in your eggs thus preventing the formation of ice crystals when the temperature is lowered. One of the earliest successful cryoprotectants trialed in the 1940’s was in-fact glycerol, the same compound used in early automotive anti-freeze products – I bet that was good for the eggs eh?

With the slow freezing method, once the cells have been dehydrated through the substitution of water with anti-freeze, the temperature is lowered at a very slow rate of less than 1ºC per min before freezing to -196ºC in liquid nitrogen. In comparison, vitrification brings the egg cells to -196ºC very rapidly, at rates of around 25,000ºC per minute. Because of the different cooling rates, slow freezing takes approximately 2-3 hours, compared to vitrification which takes place in just 15 minutes.

The quality of egg freezing is dependent on the clinic you go to

The success of either cryopreservation technique is dependent on the ability of the protocol applied to:

• minimize damage to the cells structures during the substitution of the egg’s free-water for the cryoprotectant
• avoid ice crystal formation during cooling, and
• ensuring the cryoprotectant does not poison the cells.

These outcomes are within the control of the people running your fertility clinic’s lab and so their success rates are largely a function of their quality management systems, equipment, training, and individual skill sets so keep this in mind when choosing a clinic and your preferred method of oocyte cryopreservation!

The risk and effectiveness of freezing your eggs

Okay, so egg freezing is still a new technology so of course you’re going to want to know about the risks and how effective it is right? Well fortunately there have been some great scientific journal articles being published recently with these questions in mind.

So I did the hard work and read them and I can now officially tell all of you busy women out there, that the current state of medical knowledge says that freezing eggs is a safe and effective thing to do to preserve your fertility.

A review (conducted by people with way more time to look into this stuff than Yours Truly) of every English article published from 1980 to 2013 reported the following:

• There were no differences between vitrified eggs and fresh eggs in terms of ongoing pregnancy, top-quality embryos, embryo cleavage, and fertilization (Cobo et. al 2011).
• The incidence of congenital anomalies was not increased in babies born from frozen eggs compared to those conceived naturally (Noyes et. al 2009).

In case you were wondering what some of these terms mean, like me when I first read them, what these findings are saying is that you have just as much likelihood of getting pregnant, sustaining that pregnancy and having a healthy baby with thawed frozen eggs as you do with fresh eggs, AND, that the chance of there being something wrong with your frozen-egg-made-baby is also the same as that for those made the good old-fashioned way.

In short, to my best knowledge, thawed frozen eggs are safe and effective! Good news!!

Wait…right?

What the American Society for Reproductive Medicine Guidelines is really saying about the safety of egg freezing

There are a lot of egg freezing articles out there that mention the American Society for Reproductive Medicine (ASRM) “lifting the experimental label” on egg freezing in 2012, but few give little more information on this subject than the headline. Based on some of the commentary I have read, I wonder how many journalists actually read the 7-page article…

In any case you haven’t found this information elsewhere (because I haven’t!) here are some of the key points I have extracted from the expert guidelines:

• This expert committee formed their view based on 80 peer reviewed articles concerning the effectiveness of freezing eggs, and 32 concerning safety (many of which I have referenced through-out this blog).
• There were only 4 randomized controlled trials (the highest standard in scientific study!) which found that success rates using fresh or frozen eggs in IVF were similar. But these trials were conducted on healthy YOUNG women under the age of 30, which is not the application many people are thinking about when choosing to freeze their eggs.
• The ASRM also noted that the randomized controlled trials were only published by the best and most successful fertility clinics, and hence the results should not necessarily be generalized across ALL clinics. This recommendation was repeated when the ASRM looked at the actual success rate statistics from fertility clinics in the US as opposed to specific clinical trial results.
• Only two studies were referenced looking into the short term risks to babies born from frozen eggs. 1100 babies were included in these studies combined  (which is not very many).

Here are a couple of quotes from the ASRM Guideline you might want to read (American Society for Reproductive Medicine 2013):

“While short-term data appear reassuring, long term data on developmental outcomes and safety data in diverse (older) populations are lacking.”

“…it is too soon to conclude that the incidence of anomalies and developmental abnormalities of children born from cryopreserved oocytes [eggs] is similar to those born from cryopreserved embryos.”

“There are not yet sufficient data to recommend oocyte cryopreservation for the sole purpose of circumventing reproductive ageing in healthy women.”

So is freezing your eggs a safe and effective form of fertility preservation or not?

You must be a genius if you’re not confused by now

The previous two sections are bound to confuse the heck out of you since I first told you that science says that egg freezing is safe and then went on to share some pretty apprehensive statements made by one of the world’s leading reproductive medical organizations.

The answer to your confusion lies in understanding the weasel words, and the responsibilities of the people saying them:

• Clarification 1: Did you notice that I said “to our best knowledge” in my “in short sentence”? I did that because I know from reading the journals, that while almost all of the studies conducted to date demonstrate that egg freezing is safe and effective, the actual quantity of good quality data, collected over long-term studies is pretty limited still.
• Clarification 2: Part of being the respected authority on reproductive medicine that the ASRM have become requires that they are inherently conservative with their recommendations. They know that people will make BIG decisions based on what they say (think government policy makers, and insurance companies as well as all the fertility specialists out there) so they will naturally error on the side of caution and seek to avoid making bold statements that can be misconstrued in anyway.

It is disappointing to note that some media outlets have managed to do you a disservice, despite the ASRM’s best efforts, by only quoting the final sentence in the ASRM committee recommendation, i.e. “this technique should no longer be considered experimental”.

In-line with my mission I’m not trying to convince you one way or the other with egg freezing because I know you can make up your own mind if you have all the information in front of you. As your trusted independent adviser, my goal is to find, filter, interpret and present you with the best possible information so that you can make those big decisions concerning your fertility for yourself.

So just to clarify in a better two-liner: There are some good scientific studies showing egg freezing is safe and effective, BUT there isn’t ENOUGH information out there to say this without qualification. If it were me I would feel pretty safe and secure about using it, however, it is your body not mine and these are the facts at this point in time.

You can quote me on that ☺

A 2015 ANALYSIS on the safety of freezing eggs

Finally, when I was doing my research, I thought that all of the above references were a little bit old given that it was half-way through 2015 by the time I finished this blog post (after starting it in February!) Rest assured however, that the research community is continuing to punch-out more positive results in favor of egg freezing.

For example, a great study conducted by researchers from New York University Medical Centre in 2015 found that eggs that had been frozen for 3.5 years on average worked just as well as fresh eggs in subsequent IVF cycles (Goldman et al. 2015).

Egg freezing risks – what about ovarian hyper-stimulation?

The main risk associated with freezing your eggs is ovarian hyper stimulation. Wait, hyper-what??!

Ovarian hyperstimulation syndrome (OHSS) is a potentially life threatening complication associated with egg harvesting during IVF. Stimulation of the ovaries to make them release multiple eggs during collection makes them swell and OHSS occurs when the ovaries are OVER stimulated making them twist which blocks the main blood supply.

Even worse still, OHSS can also cause the ovaries to rupture and hemorrhage resulting in internal bleeding.

Fortunately for egg freezers, the risk of getting OHSS during egg harvesting is very low (Gera et al. 2010). Severe OHSS usually only develops after the transfer of a fertilized fresh embryo which obviously is the step in the IVF process you’re planning on putting off for several years when you decide on freezing your eggs.

However, although slight, it is still a risk, so I would advise reading more about it if you are worried.

What is the “best” age to be freezing your eggs?

Describing the best age to be freezing your eggs has got to be one of the most important, yet difficult questions to answer without adding a wide range of qualifications. It’s taken me a long time to get my head around this question and here is the very neat version of what I have come up with…

Freezing eggs – the technical answer on the best time to do it

Technically speaking, the quality of your eggs is best between the ages of about 26 – 30, and is only marginally worse between 31 – 34 as the graphs below depict.

Figure 1. Percentage of embryos produced by women that have the correct number of chromosomes (i.e. good quality eggs) (Franasiak 2014).

So ignoring all other factors, from a strictly medical point of view, it is best to freeze your eggs by 35 if you want the best quality eggs available.

Freezing your eggs – the comprehensive answer on the best time to do it 

But of course there is more to this massive life decision than just the technical side.

The cost of egg freezing is not to be taken lightly at a cool $7,000 – $15,000 per collection cycle, depending on what country you live in. And then, again depending on where you live, anywhere from $100 to $1,500 per year for storage after that.

And if you then want to use these frozen eggs you’ll be looking at taking a $2,000 – $6,000 hit for thawing, fertilization, and culturing, quickly followed by a $3,000 – $10,000 charge for embryo transfer, assuming you’re lucky enough to get this far! So we are talking about some serious coin here alright!

Then there are the alternative options available to you. Why not just wait until you’re ready, save your money then spend it all on getting top-notch IVF instead? Or what about having your ovarian tissue frozen instead of your eggs (yes, this is another, albeit still “experimental” way to preserve your fertility).

Do you see why I said this is a difficult question to answer?

Finally some good analysis

The good news is, there have been some amazing studies published in the last few years that have done a pretty fine job of answering ALL of these questions with critics describing the models used in a 2015 paper as being “some of the best they’ve seen” in terms of data inputs (American Association for the Advancement of Science 2015).

The “best” age to freeze eggs

According to the analysis conducted by Mesen et. al 2015, if you plan to try and have children IF AND ONLY IF you find (and marry) Mr Right, the “best” age to freeze your eggs from a cost benefit perspective is 35 years of age.

However, your chances of having children in the future using your frozen eggs from when you were 35 are only slightly higher than using standard IVF on your older eggs. This weird result is because the increased benefit of having “younger” eggs to do IVF with is offset by the decreasing likelihood of getting married as you get older.

Egg freezing is also going to be much more expensive financially so this works against it in the cost benefit analysis too.

The world looks quite different however if you intend on having children with or without the man of your dreams. If you’re the sort of ‘gal who plans to have children no matter what, and will use donor sperm if need be, then the most cost effective age to freeze your eggs is 37.

You’re still likely to spend a lot more with egg freezing compared to standard IVF, but your chances of success more than double.

Be careful with using these ages however ladies, as the models used to determine the ages above assume that women have not performed fertility tests before deciding to freeze, and the results are not applicable to women with known fertility problems.

My conclusion on egg freezing for single women 

What these result show, is that before deciding if you want to go ahead with freezing your eggs or not, you should decide how bad you want to have a baby. If you are single at 35 and only want to have kids in the future if you get married, then getting married has the greatest impact on if you will have children or not, rather than the decision to freeze your eggs.

Given the massive costs faced with in order to freeze eggs, it seems the ‘rational’ thing to do in this situation would be to focus your resources on finding someone you think is worth breeding off rather than spending all your hard earned money on fertility preservation!

If on the other hand, if you’re reasonably cashed up and you believe that having babies is something you would like to do in the future, with or without a strong, handsome man to take your hormonal anger out on by your side, then getting your eggs in the freezer as a 37th birthday present to yourself is an option well worth considering.

How long can I keep my eggs frozen for?

There hasn’t been a lot of research done into how long you can keep your eggs frozen for. The best information provided by the ASRM is an underwhelming report by Parmegiani et la. 2009 that eggs thawed after two years were just as crispy and fresh as eggs thawed earlier.

Much more spectacularly however, I read that last year, a 38 year old woman successfully gave birth to a healthy baby girl from eggs she had frozen 14 years earlier at the age of 24! (Urquiza et al. 2014).

The staying-power of our eggs to survive freezing aside, the other factor to consider is quality of the incubator a.k.a your womb.

By looking at IVF success rates for women that have used donor eggs (usually provided by young women), we can see that when young eggs are available, success rates only decline by a very small amount with age showing that egg quality really is the main cause of our age related fertility decline and that with frozen eggs, our reproductive ability should continue until we hit menopause!

Figure 2. Percentages of transfers that resulted in a live birth using fresh embryos from donor eggs compared to women using their own eggs (CDC et al. 2014).

Hors d’oeuvre Madam’?

If you’re really interested in how many eggs you need to freeze, I know that waiting for me to get my “A” into “G” is not cool… so here’s a little appetizer to tide you over until the main course. In a recent interview I did with Dr Ong (yet to be published), he recommends you freeze 10-15 eggs per child if you are in your early 30’s, and 30 – 40 eggs per child if you’re older than this. Or perhaps you prefer the numbers published in the German medical publication, Deutsches Arzteblatt International, shown in the table below?

A Final Word

While freezing your eggs is the most effective way to preserve your fertility there a many other things that affect your fertility besides ageing. With this in mind I have put together a very comprehensive 5 page fertility plan checklist that includes everything you need to possibly think about from your young 20’s and into your 40’s, whether you are preparing to have children in the future and also if you are trying to have kids currently or struggling with infertility. It pretty much contains everything I wish I had known both prior to having kids and during my struggle of trying to get pregnant and my hope is that it can help give you some additional information that you may not elsewhere in order to support you on your fertility journey.

Also, there are just a couple of things I didn’t manage to include anywhere else in this introductory article on how to freeze eggs that I wanted to make sure we’re clear on:

• Having a larger number of your eggs collected now for egg freezing won’t make a significant difference to how many you have left. You have tens of thousands left in your ovaries so even a few hundred won’t be missed if you whip them out early to put in the freezer with the peas and pork-chops.
• If you have irregular periods, or even PCOS, you can still have your eggs collected for freezing.

And finally, the ASRM have warned that to freeze eggs for the purposes of deferring childbearing may give women false hope, and I think we’d be wise to heed this warning. While freezing your eggs is a great way to keep your chances of having a baby alive as you enter your forties, it certainly isn’t a guarantee, and we should be cautious about making any life decisions (or indecisions) on the presumption that because we have frozen eggs, we’ll be able to have children.

Stay-tuned for more on this topic soon!

Xo Kym

Kym Campbell

Since 2010, Kym Campbell has used evidence-based diet and lifestyle interventions to manage her PCOS. After getting her symptoms under control and falling pregnant naturally, Kym now advocates for dietary change as part of any PCOS treatment plan. Combining rigorous science and clinical advice with a pragmatic approach to habit change, Kym is on a mission to show other women how to take back control of their health and fertility. Read more about Kym and her team here.

Back to Top

References

Lassalle B, Testart J, and Renard J.P. Human embryo features that influence the success of cryopreservation with the use of 1,2 propanediol. Fertility and Sterility, 1985. Does oocyte banking for anticipated gamete exhaustion influence future relational and reproductive choices? A follow-up of bankers and non-bankers.

Stoop D, Maes E, Polyzos N.P, Verheyen G, Tournaye H, Nekkebroeck J. Does oocyte banking for anticipated gamete exhaustion influence future relational and reproductive choices? A follow-up of bankers and non-bankers, Human Reproduction, 2015.

Grifo J.A, Noyes N. Delivery rate using cryopreserved oocytes is comparable to conventional in vitro fertilization using fresh oocytes: potential fertility preservation for female cancer patients, Fertility and Sterility, 2010.

Cobo A, Kuwayama M, Perez S, Ruiz A, Pellicer A, Remohi J. Comparison of concomitant outcome achieved with fresh and cryopreserved donor oocytes vitrified by the Cryotop method. Fertility and Sterility, 2008.

Rienzi L, Romano S, Albricci L, Maggiulli R, Capalbo A, Baroni E, et al. Embryo development of fresh ‘versus’ vitrified metaphase II oocytes after ICSI: a prospective randomized sibling-oocyte study.

Hum Reproduction, 2010.’

Cao YX, Xing Q, Li L, Cong L, Zhang ZG, Wei ZL, et al. Comparison of survival and embryonic development in human oocytes cryopreserved by slow-freezing and vitrification. Fertility and Sterility, 2009.

Smith GD, Serafini PC, Fioravanti J, Yadid I, Coslovsky M, Hassun P, et al. Prospective randomized comparison of human oocyte cryopreservation with slow-rate freezing or vitrification.  Fertility and Sterility, 2010

Cobo A, Meseguer M, Remohi J, Pellicer A. Use of cryo-banked oocytes in an ovum donation programme: a prospective, randomized, controlled, clinical trial. Human Reproduction, 2010.

Cobo A, Diaz C. Clinical application of oocyte vitrification: a systematic review and meta-analysis of randomized controlled trials, Fertility and Sterility, 2011.

Noyes  N,  Porcu  E,  Borini  A.  Over  900  oocyte  cryopreservation babies  born  with  no  apparent  increase  in  congenital  anomalies, Reproductive Biomedicine Online, 2009.

The Practice Committee of the American Society for Reproductive Medicine and the Society for Assisted Reproductive Technology, Fertility and Sterility, 2013) 

Goldman K.N,  Kramer Y, Hodes-Wertz B, Noyes N, McCaffrey C, Grifo J.A. Long-term cryopreservation of human oocytes does not increase embryonic aneuploidy, Fertility and Sterility, 2015.

Gera P.S, Tatpati L.L, Allemand M.C, Wentworth M.A, Coddington C.C. Ovarian hyperstimulation syndrome: steps to maximize success and minimize effect for assisted reproductive outcome, Fertility and Sterility, 2010.

Jason M. Franasiak J.M, Forman E.J, Hong K.H, Werner M.D, Upham K.M, Treff N.R, Scott R.T. The nature of aneuploidy with increasing age of the female partner: a review of 15,169 consecutive trophectoderm biopsies evaluated with comprehensive chromosomal screening, Fertility and Sterility, 2014.

http://news.sciencemag.org/biology/2015/05/how-long-should-woman-wait-freeze-her-eggs

Mesen T.B, Mersereau J.E, Kane J.B, Steiner A.Z. Optimal timing for elective egg freezing, Fertility and Sterility, 2015.

Parmegiani L, Garello C, Granella F, Guidetti D, Bernardi S, Cognigni GE, et al. Long-term cryostorage does not adversely affect the outcome of oocyte thawing cycles. Reproductive Biomedicine Online, 2009.

Urquiza M.F, Carretero I, Cano Carabajal P.R, Pasqualini R.A, Felici M.M, Pasqualini R.S, Quintans C.J. Successful live birth from oocytes after more than 14 years of cryopreservation, Journal of Assisted Reproductive Genetics, 2014.

Centers for Disease Control and Prevention, American Society for Reproductive Medicine, Society for Assisted Reproductive Technology, 2012 Assisted Reproductive Technology National Summary Report, 2014.

Von Wolff M, Germeyer A, Nawroth F. Fertility preservation for non-medical reasons – controversial, but increasingly common, Deutsches Arzteblatt International, 2015.