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).
Approximately 40-50% of fertilized eggs (aka embryos) make it to the blastocyst stage. However, this number can vary depending on several factors, including the mother's age and the quality of the eggs and sperm.
That said, Dr. Zore puts the percentage of mature retrieved eggs that get fertilized, make it to the day 3 embryo stage, and ultimately to the day 5 or 6 blastocyst stage at around 30%-50%, depending on age and other infertility factors.
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.
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).
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.
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].
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).
In addition, this gender bias was consistent whether the blastocyst was biopsied on Day 5 or Day 6. Among those biopsied on Day 5, 149 infants were females and 188 were males. Among those biopsied on Day 6, 90 infants were females and 108 were males.
A morphologically “perfect” day 5 embryo transfer would be a 4AA; good expansion and excellent inner cell mass and trophectoderm. When a blastocyst scores 5AA on day five the blastocyst is starting to “hatch” with normal appearing inner cell mass and trophectoderm.
It found that the best chance of live birth was seen when around 15 eggs were collected. However, as many other studies have shown, the chance of success began to decline after 20 eggs were retrieved.
Fascinating research examining the link between live birth rates and the number of eggs retrieved in one in vitro fertilization (IVF) cycle indicate that 15 may be the “magic number” to collect for the most successful outcomes.
On average, we normally expect 70-80% of eggs to fertilise during an IVF cycle. Some embryos do not develop normally. Embryonic development can halt for many reasons, such as poor egg quality or the presence of genetic abnormalities.
If we only got 3 eggs and all 3 fertilized, that's going to be a good outcome for that cycle. However, that is the first step of fertilization. Then, depending on the age, what we want is day 5 embryos, blastocysts. If we have 3 embryos and the patient is 32, it seems quite likely that we may get 1 or 2 blastocysts.
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.
You are 3- 6% more likely to have a baby boy than a girl when using IVF to conceive. IVF increases the odds of a boy from 51 in 100 when conceived naturally to 56 in 100 with IVF.
Reproductive technologies have advanced significantly, and now lab tests can identify the gender of an embryo in the earliest stages of development. In conjunction with in vitro fertilization (IVF), these tests allow patients the option of gender selection at their personal fertility clinic.
Research has shown that if you wait for the embryo to reach the blastocyst stage before transfer, instead of performing the transfer at day 3, that sex ratio of the embryos is altered so that there are a higher percentage of male babies. Animal data has shown the increase in altered sex ratio in multiple species.
The average rates of egg development are as follows: Maturity – 80% of all retrieved eggs. Fertilization – 80% of all mature eggs. Embryo utilization – 30-40% of fertilized eggs/total embryos.
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. If, for example, we have 10 embryos on day 3 and we select two to transfer on day 3, we may not select the right embryos.
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 the same OS cycles, the euploid rate, aneuploid rate and mosaic rate of day 5 blastocysts were 49.9%, 31.1% and 19.0%, respectively, while those of day 6 blastocysts were 35.7%, 41.3% and 23.0%, respectively (P < 0.001).
Day of development was correlated to embryo grade, with Day 5 producing 90.4% excellent-to-good quality blastocysts (AA, BA, AB), compared to 70% and 45.2% for Days 6 and 7, respectively. Yet, the implantation potential of an embryo was unaffected by day of development when transferring euploid embryos (Table 2).
In the women >40 years of age, the blastocyst development rate was 22.2%, and in the younger group, the rate was 40.5%. The pregnancy rate and implantation rate in the > or =40-year age group were 21.1% and 8.9%, respectively; corresponding rates in the younger group were 44.6% and 19.9%.