Women under 38 in our IVF program have acceptable live birth rates even with only 3 – 6 eggs, do better with more than 6 eggs, and do best with more than 10 eggs. Women 38-40 and 41-42 years old have low live birth rates with low egg numbers. Success rates are much better when relatively high egg numbers are obtained.
How many of my eggs will fertilize? On average most patients will have 70-85% of their mature eggs fertilize. Immature eggs cannot be injected (ICSI) and will not fertilize in standard IVF. If the eggs are poorer quality and/or the sperm used is very poor, the fertilization may be lower than for the average patient.
As a general rule of thumb, at RMA New Jersey, which has one of the best embryology labs in the country (as evidenced by the clinic's high success rates), about 80 percent of eggs will fertilize (day 1 success), and of those, about 30-50 percent will make it to the blastocyst stage (day 5 or 6).
Of the mature eggs that are successfully fertilized, about 80% of them will make it to the day 3 embryo stage.
On average, only 30 to 50 percent of embryos make it to the blastocyst stage. The failure of some embryos to not make it to the blastocyst stage is most likely due to a defect in the embryo.
Remember, even if all of your embryos are perfect on day 3, on average only 40-50% of them will become blastocyst on day 5.
According to the Human Fertilisation and Embryology Authority (HEFA), only 20% to 30% of fertilised eggs will reach the blastocyst stage. If embryos do reach this stage, there is a higher chance of implantation and a successful pregnancy.
In fact, RMA research has shown that women with three normal embryos have a 95 percent chance of pregnancy. Now, if a woman wants to have two children, 12 mature eggs will likely not be enough unless she is young, and most eggs result in genetically normal embryos.
Women under 38 in our IVF program have acceptable live birth rates even with only 3 – 6 eggs, do better with more than 6 eggs, and do best with more than 10 eggs. Women 38-40 and 41-42 years old have low live birth rates with low egg numbers. Success rates are much better when relatively high egg numbers are obtained.
Embryo arrest
Approximately 60% of fertilised eggs become blastocysts. This means that around 40% of embryos stop growing before becoming a day 5–6 embryo.
Day 7 blastocyst accounts for ~ 5–8% of total blastocysts [6]. Although most human IVF laboratories culture human embryos to Day 6, an extended Day 7 culture is necessary for some patients, especially if patients have limited number of oocytes [6,7,8].
SET-IVF allows for the transfer of only one embryo at a time. This drastically decreases the chance of twins (or more) from being conceived, as well as complications that may arise from higher-risk pregnancies and births.
Some embryos have reached blastocyst stage by day 5 and others not until day 6 or even day 7. Recently, a study reported that the blastulation rate was 66% on day 5, 29% on day 6, and 6% on day 7 (1).
Day 5 embryos are also called blastocysts, and only one-third of all embryos are capable of growing to this stage. Some laboratories are unable to cultivate an embryo to this stage. If your embryo develops to the blastocyst stage, it has a stronger chance of implanting because it is a superior, healthy embryo.
Studies show that women in their 20s and 30s have the most success when getting pregnant through IVF and other reproductive technologies. According to the CDC, the average percentages of assisted reproductive technology (ART) cycles that lead to a live birth are: 31% in women younger than 35 years of age.
The biggest reason those little embryos take a breather and stop growing comes back to both the quality of the eggs and the sperm. You need good fuel packs (the mitochondria) in the sperm and eggs to provide the energy needed for the intense DNA division needed to move from 2 cells to 100s of cells or a Day 5 embryo.
Of those fertilised eggs, around 15% will be lost before implantation begins. Of those which begin to implant, only about half will implant successfully. Of the half which do implant successfully (as shown by detectable HCG in the woman's urine), between one third and one half will be lost at the time of the menses.
In humans, a fertilized egg is no guarantee of reproductive success. Most embryos stop developing and perish within days of fertilization, usually because they have an abnormal number of chromosomes.
Between one-third and one-half of all fertilized eggs never fully implant. A pregnancy is considered to be established only after implantation is complete. Source: American College of Obstetricans and Gynecologists.
In most cases, women under the age of 38 – as well as women who have had fewer than two unsuccessful embryo transfers – are typically recommended to transfer two embryos. This is because the rate of implantation is generally lower for older women, so the number of transferred embryos may go up with age.
Two-thirds of all human embryos fail to develop successfully.
A number of studies (1, 2) published recently suggest that cumulative live IVF birth rates increase significantly with the number of eggs retrieved.
Also, about 1% of implanting embryos will split into identical twins. As a result, even when “only” two embryos are transferred, triplet pregnancy can still occur. The risks of low birth weight and prematurity are not to be taken lightly.