Embryologists can have a different opinion on what makes the qualities of these features good, fair or poor. Every effort is made to provide accurate and up-to-date information. For cleavage stage embryos, or day 2 or day 3 embryos, these features are typically: For morulas, these features are typically: For blastocysts, these features are typically: In addition, the number of days it took the embryo to become a specific stage is considered. Because the cells can slip out easily, the zona doesnt thin out as the embryo grows. The https:// ensures that you are connecting to the Embryos that have 8 cells on day 3 are dividing faster than embryos with 6 cells on day 3. We found no evidence of altered IR or other clinical outcomes in the transfer of FH euploid embryos. ): But this doesnt mean that an embryos grade will dictate whether or not the embryo will implant. There are 3 stages to an embryos expansion: early (1-2), expanding (3-4), hatching (5) and hatched (6). My friend had identical twins from her first fully hatched blastocyst FET. Hatching and fully hatched blasts have similar rates of success, there are some studies that suggest that fully hatched could be more fragile. The embryos DNA comes together after the sperm and egg DNA combine during fertilization, but the resulting embryos DNA (genome) isnt ready yet. The expansion is the number portion and goes from 1-6, while the quality of the ICM and trophectoderm is indicated by a letter, where A is good, B is fair and C is poor. Reminder: I have an integrated glossary in the text (terms are underlined with a dotted black line, and when you tap on it a window will pop up with the definition). NickieB. Of course, the slow embryos that had blastocyst formation by day 6 and went on to expand, hatch, implant and make babies were strong and healthy all along just slower starters. Some evidence suggests a hatching blastocyst is more likely to split into twins although other studies have found no significant increase. Occasionally you might find that your embryos grade changes. Why did my embryo grade change after it was thawed? Let's start by reviewing how blastocysts are graded: NUMBER: The number refers to the degree of expansion of the embryo's cavity and goes from 2-6. Success rates are high for hatching or hatched blastos- Best of luck! Or is a 3BA better than a 3AB? Researchers are divided whether this is a good sign or something to worry about. Create an account or log in to participate. Before reading this please be aware that these success rates are based on large groups of women who were all treated in similar ways, at the same clinic (usually), with similar backgrounds (baseline characteristics, such as age, BMI, diagnosis, etc.). My clinic also does assisted hatching. Pioneered assisted hatching in Colorado with significant improvements to IVF success rates. They want to see that each cell has a nucleus and that the cells are of equal size. The ZP has multiple functions, especially during the first few days of fertilization and development. What is known already: Please select a reason for escalating this post to the WTE moderators: Connect with our community members by starting a discussion. Expected that to happen further in development in utero and afraid that since it happened early the uterus would have a higher chance of rejecting it - causing implantation to fail. Participants/materials, setting, method: Fortunately, our ever-growing network of fertility specialists is on-hand to answeryourquestions. Assessment of embryo viability in assisted reproductive technology: Shortcomings of current approaches and the emerging role of mmetabolomics. 0000036007 00000 n Bad? Its not clear why clinics do this, but it may be a way for clinics to boost their success rates so they remain competitive, or theyre concerned that these embryos might have a higher chance of leading to complications. The site is secure. Hatching 5 day blastocyst. Consult with your doctor before making any treatment changes. Is a fully hatched embryo more fragile than an unhatched embryo? SHBT group showed significantly higher blastocyst formation rate (53.3 17.5 vs. 43.1 14.5%, P = 0.0098), top-quality blastocysts (71.8 vs. 53.7%, P = 0.0436), IR (43.6 vs. 27.9%, P =. Yes, avoiding a Robertsonian Translocation, but also couldn't get pregnant spontaneously (so have an unopened new pack of birth control I don't really care for in the bathroom taunting me). Embryos that are compacted, or collapsed, are difficult to evaluate for their quality because the ICM and trophectoderm may not be clearly shown. Embryos were classified as NFH (expansion Grade 3, 4 or 5) or FH (expansion Grade 6) cohorts. Members of our FHH community (download the free app here) often reach out to us seeking clarification on fertility treatment. The pregnancy rate per cycle and implantation rate per transferred embryo was 42.1% and 19.4%, respectively, in the blastocyst group compared to 23.6% and 8.6%, respectively, when embryos were transferred on day 2. We would definitely push for the blastocyst stage (day 5) due to the extra information that we get from the development from day 3 to day 5 (impact of the sperm dominance from day 3 onwards). Results: Of 676 euploid embryos included in this analysis, 464 were expanded or hatching (Ex/HgBl) and 212 were completely hatched (CHBl) at the time of transfer. 5 = embryo has expanded so far that it has . FET #2 - June 2017. I will not grade the embryo, since this is best done by your embryologist who had access to the microscope. (2011), younger women <33 years old with high quality blastocysts have a 59.9% chance of live birth, while older women >38 years old with high quality blastocysts have a 32.6% of live birth. These results suggest that reduced success rates associated with fresh transfers of later developing blastocysts may be the result of asynchrony with endometrial receptivity instead of poorer embryo quality. In my opinion these are the strongest embryo to get! (2018). Transferred two each time Last cycle resulted in miscarriage at 8 weeks due to trisomy. I was so sure it would work first go round for me, since didn't have any history of fertility issues and was young (30). We have done blastocyst culture and transfer since 1998. Why do embryos arrest, or stop developing, and dont become blastocysts? (2022), which looks at the % of mature eggs that go on to form blastocysts: You can read the full study in my post Age-specific blastocyst conversion rates and other IVF outcomes in good prognosis women. Even the best of the best, a PGT-A tested euploid embryo, doesnt always work! Timing of blast development: Day 5, 6 or 7? I recall you are doing ivf to avoid passing genetic condition to offspring - which is same reason I'm here too. Use of this site is subject to our terms of use and privacy policy. I have one 6-day embryo. After the fertilised egg undergoes embryo culture for 2-6 days, it is . I'm currently 4dp5dt. We strive to provide you with a high quality community experience. If youre having trouble getting pregnant, you might be considering IVF as a next step. Please specify a reason for deleting this reply from the community. HHS Vulnerability Disclosure, Help This would be described as a hatching blastocyst with the highest quality ICM cells (first letter) and the highest quality TE cells (second letter). Poor quality embryos work check your clinics policy on discarding them, Blastocyst embryo grading (Day 5 grading), Variability in expansion embryo grades by clinic or embryologist, ICM and trophectoderm grading for early blastocysts, Embryo compaction may make embryo grading difficult, How blastocyst embryo grades are reported, Day 5 (blastocyst) embryo grades and pictures. The rate of triplets with blast transfers at our IVF center has been about 2% of pregnancies. (2019)took a closer look at embryos with more than 10 cells on day 3. Artificial insemination delivers sperm directly to the cervix or uterus to achieve pregnancy. While its relatively easy to count the number of cells you see in a day 3 embryo, cell appearance is harder to grade. Wijnland emphasizes that additional treatments like assisted hatching should only be offered to cases that meet the criteria so assisted hatching isnt suitable for every patient going through IVF. How many day 3 embryos make it to blastocyst? For blastocyst stage embryos (day 5, 6 or 7), embryo grading is based on the embryos size (expansion) and the quality of the inner cell mass (ICM) and trophectoderm. Heres a handy quick guide to help you put it all together: As mentioned, some clinics might use D in addition to ABC, while others may use A-F. Others may use grade I in place of A or use a + or - sign where an A+ would be a perfect grade. Heres an example of a cleavage stage embryo with around 8 cells: Usually around day 4 the cells undergo compaction to form a morula. I equate this to a kind of cocoon where the cells of the embryo start to change, or differentiate, into the cells of the blastocyst, which is a very different structure compared to the cleavage stage embryo. View their partner profile here and check out their website by clicking here. Paternal contribution to embryonic competence. This uses a number followed by two letters, where the number indicates the embryos expansion (from 1-6) and the quality (A, B or C) of the inner cell mass (ICM) and trophectoderm. 0000004461 00000 n 0000021606 00000 n and more of your hatching-blastocyst questions. Conclusions: In frozen embryo transfers with euploid, good morphologic quality embryos, completely hatched blastocyts at the time of transfer resulted in a significantly lower pregnancy success compared to the transfer of expanded or hatching blastocysts. The statistics covered in this guide are highly dependent on maternal age, specifically the age of female at the time of egg retrieval. Fertility treatments take a toll on nonpregnant partners, too. Limitations include the retrospective design and data from a single institution. Your post will be hidden and deleted by moderators. 2005-2023Everyday Health, Inc., a Ziff Davis company. ( A ) Main analysis; ( B ). Rienzi L, Gracia C, Maggiulli R, LaBarbera AR, Kaser DJ, Ubaldi FM, Vanderpoel S, Racowsky C. Hum Reprod Update. Expansions of 3 and 4 are also variable. (2018) found that day 5 embryos performed better than day 6 regardless of grade (29.6% live birth vs 17.0%). Fully hatched blastocyst with clear tightly packed ICM. (2014) looked at Day 3 double embryo transfers (average age of 30). 0000001756 00000 n To date, no other study has evaluated the reproductive competence of an FH blastocyst transfer. Well talk about this in more detail below, but an embryos quality is only one part of what dictates success rates: age is very important also! Day 3 Embryo Blastocyst Example Some embryos will have 3, 5, or 6 cells, and thats because cells dont divide at the same time. A difference of 5% has been reported by Ciray et al. Epub 2021 Jul 26. 2014 Jun;29(6):1173-81. doi: 10.1093/humrep/deu033. Implantation rates also decline with female age due to a rising chance of chromosomal abnormality. The average number of embryos transferred in each group were Day 5: 1.1 ; Day 6: 1.06 ; Day 7: 1.04 (p=NS) Implantation rates were 49%, 51%, and 17%, respectively. Good quality euploids tend to perform better than fair quality, which tend to perform better than poor quality. Many clinics will stop culturing embryos at day 6, and its important for you to make sure that your clinic will culture to day 7, to give you the best shot at getting as many embryos as you can. Do the reproductive outcomes from the transfer of fully hatched (FH) blastocysts differ from those of not fully hatched (NFH) blastocysts? My clinic just puts a blanket name of pgd over all the testing. Some evidence suggests a hatching blastocyst is more likely to split into twins although other studies have found no significant increase. Bromer JG, et al. We keep them up because there are a ton of great conversations here and we believe you deserve to see them all. 0000005130 00000 n Our 28 month old daughter was a grade 2 hatching blast but this pregnancy (18 weeks) was our worst quality embryo at a 3. . He earned his MSc in 2012 for his research on inflammation and lung cancerand started Remembryo in 2018 to help people understand the evidence behind common IVF topics. Need help understanding your day 3 embryo grade and picture? Our clinic rates embryos out of 5 with 1 being the best. PLoS One. 0000007041 00000 n Study design, size, duration: However, not all good quality embryos follow the rules. Short Protocol. 2021 Mar 18;36(4):929-940. doi: 10.1093/humrep/deab014. As you may have guessed from the last section on the variability of the expansion grade, there can be variability in the ICM grade. Craciunas et al. This usually happens on day 3, so by day 5 when the embryo is a blastocyst, the cells can easily hatch out. Learn about the number of eggs retrieved and IVF success, Many human embryos are chromosomally abnormal, As female age advances, the rate of chromosomal abnormalities in eggs increases substantially, At 30 years old approximately 30% of eggs (and embryos) are chromosomally abnormal, By age 37 the average rate of chromosomal abnormality is 45%, 75% of embryos are abnormal by age 42, and 90% by age 44, This is because chromosomally abnormal embryos are more likely to arrest during early development compared to chromosomally normal embryos, Therefore, day 5 embryo transfer has a filtering effect weeding out some of the chromosomally abnormal embryos, Unfortunately, many chromosomally abnormal embryos form good looking blastocysts, To do more reliable screening for chromosomally abnormal embryos we can do preimplantation genetic screening PGS, PGS is done by biopsying day 5 or day 6 blastocysts and performing chromosomal testing on the biopsied cells, The embryos are frozen after the biopsy and transferred later after genetic test results are back. Your embryo is super strong and continued to do its thing after the thaw. Long Protocol. Vitrified embryos from 2-cell to early blastocyst stage showed similar blastocyst (71.8-89.5%) and hatched blastocyst rates (61.1-69.6%) and could develop to term without a significant loss of . Similarly, there was no significant difference in fetal cardiac activity rates between Ex/HgBl and CHBl with morphologic grades BB and < BB (p=0.17). a valuable technique to use in the laboratory for PGT-A cases. Check the full summary in my post Comparable outcomes with good quality day 6 and poor quality day 5 embryos. (2011). As it grows in size, the embryo stretches and thins out the zona. I really like that graph above because it also shows how age plays into things. Instead of air, the embryo is filled with water and gets bigger, or expands, over time. 0000058651 00000 n o#EaKNux70313`tAmV@7K -g`PbA H+00p>@ =1i@ - Poor quality embryos included embryo grades 6CA, 6AC, 6CB, 6BC, 6CC, 5CA, 5AC, 5CB, 5BC, 5CC, 4CA, 4AC, 4CB, 4BC, 4CC, 3CA, 3AC, 3CB, 3BC and 3CC, which had a live. In a few months I will be doing a natural FET. 0000004913 00000 n Which is comparatively high to the alternative freezing method called slow freeze with an 86% survival rate. government site. Yes, you can get pregnant if an embryo is transferred earlier (day 3) but it must reach the blastocyst stage within the uterus. Good quality day 3 embryos tend to have a higher chance of making it to blastocyst. Some think it may be a way for the blastocyst to help the hatching process. During the thawing process the embryo fully hatched from its shell prior to transfer. Methods are provided for the non-invasive imaging of embryos to determine whether they are euploid or aneuploid. However the miscarriage rate was lower when there was more than 10 cells. The blastocoel is full at expansion stage 3 and by 3 to 4 the embryo itself is starting to grow larger. Storr et al. A Group Leader is a What to Expect community member who has been selected by our staff to help maintain a positive, supportive tone within a group. Some clinics will also only call the embryo a 5 if there are many cells hatching out, while others have a lower threshold and might only require a single cell to be hatching out. 0000004090 00000 n So if youve gotten this far in this guide, it should be clear to you that embryo grades matter. Again, the trophectoderm grade can be variable depending on the embryologist. 0000004386 00000 n James et al. The blastocyst continues to develop until it reaches the hatching stage. (2020) found that good prognosis women who transferred up to 3 euploid embryos (one at a time, for a total of three transfers) had a cumulative live birth rates of 92.6% by the third transfer. Clinics can have different ways of reporting grades. Heads up: Blastocyst grading is complex and that means that grades arent carved in stone and may change. I found one from NYU that says 1dp5dt the embryo begins hatching out of its shell and 2dp5dt It continues to hatch and begins to attach to the uterine wall. IVF pregnancy with fully hatched embryo. (2005). *. Unauthorized use of these marks is strictly prohibited. During my second round of IVF/ICSI I also got 4 blasts again. Fresh and FET cycles and associated clinical outcomes were considered separately. Yellow shows success rates for day 5 blast transfers Fair quality embryos included embryo grades 6BB, 5BB, 4BB and 3BB, which had a live birth rate of 39.0%. 0000003521 00000 n 0000005199 00000 n Assisted hatching (AH) is one of these add-ons and was first suggested in the 1980s. Embryos can be artificially compacted, or collapsed, by using a laser. 0000058518 00000 n Factors associated with vitrification-warming survival in 6167 euploid blastocysts. My first son was a hatching blast (both sons are pgd singleton) and my last was getting ready to hatch (plumping up on one side). This refers to the quality of the embryo, or grade. 0000004612 00000 n Thankfully, there is no variability in a 6. My first FET (chemical pregnancy) was a 5 day embryo. Most cleavage stage transfers these days are day 3 transfers, with fewer performing day 2 transfers. In fact, there are 5 cells that are in focus, with one cell on top and two below. Below are in vitro fertilization live birth success rates at our fertility clinic with fresh embryos according to the day of the embryo transfer procedure and female age. Secondary outcomes were also statistically similar between groups: BPR (65.9% versus 66.7%, OR 1.0; 95% CI: 0.6-1.6), LBR (43.1% versus 47.7%, P = 0.45, OR 1.2; 95% CI: 0.7-1.9) and EPL rate (22.8% versus 18.2%, OR 1.3; 95% CI: 0.7-2.4). Another more personalized way of figuring out how many blastocysts will develop is to use the nomogram developed by Jin et al. All rights reserved. Lets dive in. Embryo grading is very subjective, and not all embryos will grade embryos the same. Good Luck!!!! I just had a FET today. (The size of the cake doesnt change when you slice it, but the number of pieces does.). Youll likely need them soon. There was no statistical difference in miscarriages (13.7% vs 14.6% vs 19.1% vs 18.7%). You can see the graph below that shows how different blastocyst ICM and trophectoderm qualities correspond to live birth rates: This study also looked at frozen transfers and how the embryos expansion plays into this. 0000057970 00000 n Otherwise, Without all the blood tests, scans and the like I don't think we would have known I was pregnant for a while. My embryo was almost fully out of its shell. Pirtea et al. The best way to get accurate statistics will be from your clinic. Your embryo (now called a blastocyst) is hard at work dividing and building up the number of cells. Transferred one perfect 6AA fully hatched blastocyst - BFN! Answer from: Andrew Thomson, FRCPath Andrew Thomson, FRCPath Which is what made us decide to have our next batch PGS and PGD tested. We have broken down the system we use for grading blastocyst success at ORM in the following chart: NUMBER: The degree of the expansion of the embryo's cavity, ranging from 2-6. The educational health content on What To Expect is reviewed by our medical review board and team of experts to be up-to-date and in line with the latest evidence-based medical information and accepted health guidelines, including the medically reviewed What to Expect books by Heidi Murkoff. The ICM is the part of the embryo that develops into the fetus and is indicated by the first letter in the embryo grade (the A in 4AB). More than 1.5 percent of all babies born annually in the United States are the result of ART or babies born from pregnancies that were possible thanks to assisted reproductive technology. 0000034981 00000 n Reaching the end of the fertility trail with a prize to cuddle can be a physically and emotionally draining trek that covers so much uncharted territory. There is no guarantee of an improved live birth rate. Think of this as studying the chemical fingerprints left behind by processes that happen in the cell. Infertility can affect your mental health. If youre still confused after all of this and you want some extra help to understand your picture, I offer a service where I record a video and go over your picture for a fee. Fully hatched blastocysts (n73) showed a signicantly lower PR (42%) when compared to blastocysts with a blastocoel of more than . Generally, embryos with a high degree of fragmentation also show signs of irregular symmetry, because as fragments are lost the cell itself gets smaller. Error bars represent 95% confidence interval (CI). think twice before sharing personal details, foster a friendly and supportive environment, remove fake accounts, spam and misinformation, delete posts that violate our community guidelines, reviewed by our medical review board and team of experts. In other words is a 5BB better than a 3AA? 0000031917 00000 n There are a few techniques that can be used to perform AH and the most popular technique is by the aid of a laser. Some embryos arrest because they cant switch from the stored maternal egg factors to the embryos genome, while others have metabolic issues. The .gov means its official. 0000015984 00000 n Aside is a picture showing an embryo which has survived the thaw and fully re . On Day 5 there were three CCs and one BB. Well get into all the statistics and the studies below, so stay tuned! Variations of the system may be proprietary to a laboratory but convey the same information. The day of an embryo isnt really part of the grade, but its considered as research has shown that how fast an embryo grows relates to its chance of implanting. Heres an example of a embryo that has a thick zona (on the left), but you can see it hatching (on the right). There are a few techniques that can be used to perform AH and t. he most popular technique is by the aid of a laser. I transferred 2 in December- one fully hatched- in the picture i thought it was 3 embryos but it was the fully hatched embryo, the shell, and the 2nd embryo. Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance. Capalbo A, Rienzi L, Cimadomo D, Maggiulli R, Elliott T, Wright G, Nagy ZP, Ubaldi FM. Chi-square analysis also demonstrated a significant difference between these two groups with regards to both rates of positive -HCG and the presence of a gestational sac. Click here to view the SART Snapshot Report for AFCC. 2 = cavity fills 1/3 of the embryo 3 = partial expansion, fills 70% of the embryo 4 = fully expanded cavity 5 = embryo has expanded and split open the zona You can see the graph below that shows the impact of cell number on predicted live birth after transferring a single fresh day 3 embryo. At day 3, embryologists use a high-power microscope to take a look at the morphology (a fancy word for structure) of the embryo. and even those containing three pronuclei, can generate pluripotent hESC lines that grow well. Heres where division of labor comes in: At this point, things are getting pretty cramped inside the shell (zona pellucida or ZP for short) that surrounds the embryo and the shell is being pushed to its limits. A blastocyst is a Day 5 embryo yet to fully understand what a hatching blastocyst is, we need to explain the early development of an embryo. More than 70 weedy seadragons have hatched at Birch Aquarium in La Jolla after a first-of-its kind egg transfer in the public eye. While many embryos become blastocysts on day 5, sometimes it takes longer (day 6 or day 7). There are different stages as the embryo develops, including the cleavage stage, morula stage and the blastocyst stage. 0000004536 00000 n But I've done in the past and it only resulted in several mental breakdowns. 0000002958 00000 n By assisting with embryo hatching, the process of implantation is started. Because of inconsistencies in grading cleavage stage embryos, in 2007 the Society for Assisted Reproductive Technology (SART) began requesting its US clinic members to report data in a specific way (Racowsky et al. A 4AA would be represented as 4-3-3, a 4CC as 4-1-1. Inactive. First lets talk about the expansion (the size) of the embryo. In cases where preimplantation genetic screening (PGS) or now known as preimplantation genetic testing for aneuploidy (PGT-A), assisted hatching is one of the techniques used by laboratories prior to biopsy to optimize the biopsy procedure. 0000003069 00000 n Other studies have found a similar impact of grades on euploids, including the impact of day 5, 6 and 7 (reviewed in my post on PGT-A (PGS) success rates). Of the 464 Ex/HgBl, 60.56% developed a gestational sac, while 105 CHBl (49.53%) had developed a gestational sac at the 7-week ultrasound (p=0.007). Fragmentation is usually written as a percentage of the whole embryo. Unable to load your collection due to an error, Unable to load your delegates due to an error, Clinical outcomes of not fully hatched versus fully hatched blastocysts in fresh and FET groups. Hum Reprod. The use of extended culture and PGS often leads to transfer of an embryo that is well developed and frequently FH from the zona pellucida. This is usually after an embryo is frozen with one grade, and then gets a different grade after it was thawed. For women over 42, however, it's less than 10%. Rhenman et al. Eventually some cells start to hatch out from the zona (expansion 5) until ultimately the zona cracks open and the embryo is completely hatched (expansion 6). 0000005015 00000 n Theyre looking mainly at two things: An embryo thats dividing well should ideally have between 6 to 10 cells by day 3. Despite this increase in success rates, implantation rates have not changed significantly, remaining . Zhao et al. Years ago, it was a struggle to keep fresh embryos alive and healthy in the lab for more than 3 days. Please specify a reason for deleting this reply from the community. Hatching Blastocyst. We are here to answer any questions or concerns you may have so that you feel completely confident when taking the first step toward building your family. Read more about : Does ICSI Increase the Chances of Twins? In fact, this scenario (the presumably lower quality embryo resulting in pregnancy and birth) has played out many, many times. Ferreux L, Bourdon M, Sallem A, Santulli P, Barraud-Lange V, Le Foll N, Maignien C, Chapron C, de Ziegler D, Wolf JP, Pocate-Cheriet K. Hum Reprod. They also check for fragmentation. At this point, the blastocyst begins to prepare for implantation in the uterine wall. I had two hatching 5AA embies put back yesterday so know how you feel - just praying that implantation happens with these good quality embryos. This is crucial information to understanding embryo grading! Last cycle we had a 4AB and 4AB/C put back without success so hoping for better luck with . Cytoplasmic strings are string-like structures that can be seen in an embryo photo. How many embryos do you have on ice? 1. Zhu et al. 0000002108 00000 n So in a 1/4 theres 4 cells. Surrounding the blastocyst is the zona pellucida, or zona for short, which is like a shell that was originally present in the egg and carried on. I have two baby boys from 4 transfers thus far (2y7m and 8m). According to Goto et al. FOIA My RE assures me that people do . I really hope it works out this time for you. Becoming a blastocyst requires a massive shift in development. If youre looking for positive signs after an embryo transfer to indicate that you successfully became pregnant, there are several notable ones. Embryos reach day 5 of development but havent hatched. Our website services, content, and products are for informational purposes only. So whats a 4 to one clinic may be a 3 to another. March 4, 2023 11:43 AM PT. 0000004838 00000 n Embryo grading is used during IVF to rank embryos for transfer after evaluating different parts of the embryo. Assisted hatching can be expensive. I guess I'm trying to figure out how much the success rates decrease when the blast is a 4 instead of a 5.
