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Dr. Pat Consults: Egg Freezing and Your Future Pregnancy—What Women Need to Know

Table 1: Reasons to Consider Oocyte Vitrification 

1) “Elective” fertility preservation to reduce the effect of aging on reproductive potential.

2) Immediate threat to fertility from chemotherapy or pelvic radiation.

3) Genetic mutation requiring removal of ovaries to decrease cancer risk (BRCA mutation carriers).

4) Ovarian surgery with risk of damage to ovary.

5) Ovarian disease ( i.e., endometriosis) with risk of damage to ovary.

6) Risk of premature menopause ( 45 XO, fragile X carriers, family history).

When to Consider Egg Freezing

There are many potential reasons for women to consider oocyte cryopreservation —“freezing” their eggs (see above Table 1). The most common reasons today are to delay the natural decline in the ability to have children, due to aging, and to prevent premature infertility as a result of cancer treatment. It is very important that women who are interested in this issue get accurate information about the process, options and outcomes in order to make an informed decision.  At Cornell, we are pioneers in fertility preservation for patients facing potentially sterilizing cancer treatments as well as egg freezing to preserve fertility.

Fertility Predictors and Testing

While it would be ideal if there were a test that could predict when a woman’s fertility would start to decline or how much longer the window of fertility would remain open, there is no such test at this time. A woman’s age remains the most critical factor in determining the chances of pregnancy with either her fresh or frozen eggs. The second most important predictor of success is the total number of mature eggs available. Since the lower pregnancy rate as women get older is due to an increased probability of a genetic defect in each oocyte, the more eggs a woman has in the “bank,” the greater chance she has of one or more of the eggs being genetically normal. While freezing the eggs results in slightly lower probabilities that each egg will be successfully fertilized and continue to develop compared to fresh eggs, this reduction is relatively small, especially in women younger than 35.

Retrieving Eggs for Preservation

The process of retrieving eggs to be frozen and preserved begins with ovarian stimulation of daily hormone injections. This stimulates the production of the monthly crop of follicles containing the eggs as well as assisting in their maturity. This stimulation process can take as long as two weeks. Oocytes and the surrounding follicular fluid are then aspirated with a thin needle transvaginally with ultrasound guidance  under mild sedation. The procedure lasts about 5 to 10 minutes.

The potential yield of oocytes can be estimated in advance of ovarian stimulation by a blood test for AMH (Anti-Mullerian Hormone—a hormone produced from the very early developing eggs. The more the number of developing eggs, the higher the AMH level). Or, the estimation can occur by examination of the ovaries with a high-resolution transvaginal ultrasound that enables the early stage developing follicles to be counted. Both of these measures of “ovarian reserve” are, for the most part, quantitative estimates of how many eggs are available for recruitment each month and do not correlate to “quality.” Antral follicle counts (potential eggs available) and AMH levels are highly predictive of the number of oocytes obtained each month and can be used to counsel patients prior to treatment.

Most information regarding outcomes using cryopreserved eggs comes from studies of young egg donors, usually less than 30 years of age, whose oocytes have been cryopreserved for a short time (usually less than 6 months). Clinical pregnancy rates were between 4.5 to 12% per warmed oocyte. When pregnancy outcomes with vitrified oocytes (ultra rapid freezing) from donors were compared to fresh oocytes from the same donors, there were no significant differences in fertilization rates—the frequency of top-quality embryo development, or live birth rates.

The two most critical factors in determining the probability of achieving a live birth with the use of vitrified oocytes are the woman’s age at oocyte retrieval and the total number of oocytes available. In one study evaluating the efficiency of oocyte vitrification, the percentage of vitrified  oocytes that resulted in a live birth was 8.2% (12.1 oocytes/live birth) in patients aged 30 to 36 and 3.3% (29.6 oocytes/live birth) in patients aged 37 to 39. What this means technically is that the younger a woman is, the more eggs she will have to be retrieved each month; and each egg retrieved has a higher chance of becoming a baby compared to results for women who are older. The total number of eggs a woman over the age of 35 needs to have frozen—to have a reasonable chance of having a baby— is over 30 eggs. This might require more than one cycle of ovarian stimulation and egg retrieval to reach that goal.

The Cost

The process of freezing eggs is not inexpensive. Each cycle of stimulation, retrieval and freezing can run upwards of $10,000, not including the medications, which can range between $1,000 to $3,000 per cycle. Keeping the eggs frozen also costs around $500/year.

Interestingly, many women who freeze their eggs often do not need to use them in the future as they either meet someone and have children, without having to resort to their frozen eggs. Or, they have a change of heart about having children as a single parent if they don’t enter into a relationship with a partner in the future. Either way, having that “insurance policy” of eggs in the bank is very important to some women.

The Complications

One caveat of egg freezing and the ability to reproduce well after natural menopause is the fact that rates of pregnancy complications such as hypertension, preeclampsia, diabetes, placental insufficiency, abruption, intrauterine growth restriction and cesarean delivery are all increased in older mothers. For this reason, before starting treatment, we have patients sign a consent form regarding disposition of the eggs in case they make a decision not to use the eggs, or they are unable to use them due to illness or death. Additionally, we have an age cut-off for using these eggs. After a woman reaches 55, we will no longer keep the eggs frozen or fertilize and transfer them into her uterus in order to achieve a pregnancy. The risks to the potential child are too great.

While egg freezing is no longer considered experimental by the American Society of Reproductive Medicine, there is still insufficient outcome data to say that it is completely safe. While there does not appear to be an increased risk for congenital anomalies, the number of children born thus far from cryopreserved oocytes is small (less than 2,000 births) and the length of the follow-up period for these children is short, potentially lowering the true risk since most birth defects are not detected until after one year of age.

Women interested in having children should be counseled that there may never be a good time in one’s career or personal life to become a parent. The ideal time to effectively cryopreserve oocytes would be prior to the expected age where fertility naturally declines, i.e., early-to-mid 30s. If cryopreservation is undertaken too early, there is an increased chance that the patient will never need the stored eggs to have children, and she would therefore have been exposed to unnecessary, albeit minimal, risks of stimulation and egg retrieval. Cryopreserving eggs at a later age (older than 38 years of age) increases the risk of the procedure yielding too few and/or abnormal eggs and an extremely low probability of these eggs ever resulting in a baby.

Oocyte cryopreservation has reduced the disproportionate pressure on women to have children during a limited reproductive time period when they may have not yet found their partner or be able to take on the responsibilities and joys of parenthood. For those women, oocyte cryopreservation offers the possibility of extending that window.

 

Dr. Glenn L. Schattman is an Associate Professor of Obstetrics and Gynecology and Reproductive Medicine at The Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine (CRM) at Weill Cornell Medical College. He is board certified in Obstetrics and Gynecology and Reproductive Endocrinology and Infertility and a noted specialist in In Vitro Fertilization (IVF), fertility preservation, minimally invasive reproductive surgery and problems of sexual development in girls and young women. Dr. Schattman was the 2011-2012 President of the Society for Assisted Reproductive Technology (SART), a world-leading reproductive medicine society.

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  • Pregnancy Guide June 29, 2015 at 9:45 pm

    wow that was a very detailed article, thank you so much that really helpful.

    Reply
  • Megan Riddle June 25, 2015 at 2:26 pm

    A timely and well-balanced article. There are many reasons women may not be ready to have children in their 20s and early 30s – focusing on career, finding a spouse. For those with means, “egg freezing” can offer a certain level of insurance. I do wish the financial cost weren’t so high and it was available to more women. Maybe, as with many things, as the technology moves forward, the cost will come down.

    Reply