Determining your pregnancy due date is one of the first things that happens at your initial prenatal appointment. What are the common methods used when figuring out this date? What happens if your exact due date can’t be determined and how can it impact future treatment? Plus, what’s happens if your due date comes and goes and your baby still hasn’t arrived?
Your Pregnancy Due Date: Is It Really Important?
Episode 67, August 12th, 2013
Please be advised, this transcription was performed from a company independent of New Mommy Media, LLC. As such, translation was required which may alter the accuracy of the transcription.
[Theme Music] Lali Reddy
Lali Reddy: It’s one of the first things discussed at your initial prenatal medical appointment: your due date. Knowing the approximate date your baby is expected to arrive is an important factor in determining the best prenatal care possible. But how accurate are these due dates? And what happens if your due date comes and goes and still no baby? I’m Lali Reddy at OB/GYN with Sharp Grossmont Hospital and this is Preggie Pals, episode 67.
Sunny Gault: Welcome to Preggie Pals, broadcasting from the Birth Education Centre of San Diego. Preggie Pals is your weekly on-line on the go support group for expecting parents and those expecting to be pregnant. I’m your host, Sunny Gault. Have you joined our Preggie Pals Club? Our members get all of our archived episodes, bonus content after each new show, plus special giveaways and discounts. And you’ll also get a free subscription to pregnancy magazine, so you can’t lose. If you want more information, you can visit our website, which is Preggiepals.com. And thanks to everyone who is listening to this episode. You are awesome. Preggie Pals apps, we do have two of them, so whether do you prefer your iPhone, or your iPad, or your Android phone, we’ve got two different versions. It is the best way on my personal opinion to listen on the go, especially for parents who are always out and about, or if you are at your prenatal appointment and you are just waiting for the doctor, this is a great way to just get caught on the latest episodes. And they are free, so be sure to download our apps today.
[Theme Music] [Featured Segment: Five minute birth stories]
Sunny Gault: Before we get start with today’s show, we have a brand new segment here, on Preggie Pals. It is called “Five minute birth stories” and that’s exactly what it is. We’re asking our listeners to call our voicemail, which is 6198664775, and share your birth story in five minutes or less.
Megan Church : Hello, this is Megan Church, from Southend Indiana, and the writer of unexpected.com , and a former blogger for Preggie Pals. I just want to take a few minutes to share the birth story of my third child. My first two births have gone pretty well, and they’ve been hospital births with a midwife. When the third pregnancy came along I suddenly started to wonder if we should do a homebirth. I’ve been doing a lot of research for my book, “Unexpectant”, and suddenly had the feeling that I couldn’t be so lucky again to have a good hospital birth, especially when they didn’t end with a c-section. After talking to my midwife, I have a very good relationship with and have full confidence in, I decided that I was going to stay with the hospital. It was about 5 days before my due day and I woke up with mild contractions at 2 in the morning. My first two kids were post-due. My first child was 10 days post-due and my second one was 6 days. So at that point I was “There is no way that this is real labor, I still have about a week to go here”. So I tried just to ignore the contractions and go back to sleep. But of course my mind began racing: what to do and stuff that I wanted to do before the baby came. But the contractions didn’t progress at all until about 9 o’clock that night. At that point they started to become more regular, but is still wasn’t sure it was the real thing, I was still thinking “I’m 5 days early, there’s no way the baby can be coming right now”, and I was debating what to do about calling my parents. They were going to be watching our older two kids when we were in hospital. So I didn’t want to inconvenience them and have to come at my house too soon, and stay the night when they didn’t need too. But finally I called my mom and I said “I think it would be best if you came in to sleep the night at mine”. So by about 1:30 in the morning my parents were here and they were settled in the bed, we were ready for bed. It was about 4:30 when I finally woke my husband because my contractions were sometimes 4 minutes apart, still not regularly like I’ve had with my first two labors. But finally we started reaching that 4 minutes mark, with more consistency, and we decided it was time to go. My contractions did slow a bit on the way to the hospital, which was one of my fears, because again it happened in my first pregnancies, but thankfully they began regular again. When I was checked in triage, I was 7 centimeters, so they admitted me. At that point the nurse asked me if I wanted a water birth, and I said I definitely wanted labor in the water, but I wasn’t sure about a water birth yet. She just went on about how beautiful they were, and how great they were, and how she personally recommended them. And I said “I’ll consider it, but basically just get me in the water to labor and we’ll see after that”. The nurses did such a good job on getting the tub ready for me. As soon as I walked into the room it was ready and I was able to get into the water immediately. Even if the contractions weren’t as bad as I thought they should be, I sat in the water kind of thinking “Let’s get this show on the road already”. I was still talking and more aware than any other labor. I was a lot more present. During the others I kind of zoned out, spaced out, sort of gone and turned away. This time around I was chatting more. I kept thinking this isn’t the real thing; it’s not as intensive as it needs to. But after being in the tub for a while, things began to pick up. As I was sitting there, I turned to my husband and I said “This baby is not a girl”. The ultrasound test wasn’t 100% sure, we thought it was a girl, but couldn’t say with certainty. I kept thinking the whole time “It’s a boy, this baby’s a boy, this baby’s a boy”. So about an hour before delivering I was still sitting in the tub saying “This baby is going to be a boy”. And then transition hit, and then things got serious and definitely progressed at that point. My midwife was with another patient and the nurse has given us privacy. They said that if we needed anything there was a chord over the tub and we should pull and they’d come in immediately. So in the middle of transition, at the point when I think “I’m done, I just can’t do this anymore”, suddenly this powerful contraction gripped me. I had the urge to push. I yelled at my husband “Pull the chord, pull the chord”. He pulled it, the midwife and nurse came in right away. My midwife asked if I felt the urge to push and at that point I was pushing. After a few good, strong, hard pushes the baby was born and, yes, it was a girl, as the ultrasound test has thought and my mother’s intuition was wrong again, for the second time. For every baby of mine was a boy, and two of them ended up being girls. She was healthy, she was wonderful, the water birth was great, there were no interventions, no c-sections, no nothing. It was a beautiful birth and I couldn’t ask for anything more. Thanks for letting me share my story.
Sunny Gault: We all have them, but some are more accurate than others. Today we are learning all about the importance of pregnancy due dates. Our expert is Doctor Lali Reddy. She’s an OB/GYN with Sharp Grossmont Hospital. Welcome to the show, doctor Reddy.
Lali Reddy: Thank you, I’m so happy to be here.
Sunny Gault: Yes, we’re happy to have you. So let’s start with the basics: what exactly is a pregnancy due date?
Lali Reddy: It’s suppose to be the date your baby should be arriving, if nature obeyed all the rules, It’s actually very exact, but whether the baby comes on that date or not is not the point, really, because less than 5% of the babies are actually born on their due date. So it’s really an approximation of how long, ideally, the baby should stay within your uterus before coming out. There’s a lot of misconception about it. It’s very hard for me to translate it in terms of months, because we’re so used of thinking about it in terms of weeks. So a full pregnancy is 40 weeks from the date of your last menstrual period. The first day of your last menstrual period and add 40 weeks from there. This is kind of an international standardization and it’s a little bit misleading, because that’s really not how long the baby is inside you. You conceive your baby 2 weeks after your last menstrual period, so your due date is actually 38 weeks after you conceived the baby. So there’s always a 2 week difference between what your doctor says and how old your baby really is. So if I say you’re 20 weeks long, it means you conceive him on a magical night 18 weeks ago.
Sunny Gault: That’s a really good point to make, because I remember first being pregnant and be like “I don’t really understand this”, because they’re counting according to your last period. That’s really what they’re looking at to determine 40 weeks.
Lali Reddy: Exactly. And even that is not exactly accurate. Obviously you get pregnant when you ovulate. It would take a day or two. And you ovulate two weeks or 14 days before your next period. How do you know when that is if you got pregnant and you don’t have that next period? If you’re use to having 28 days menstrual cycles, you ovulate 14 days before your next period, which is on day 14. But let’s say you have 32 days cycle, so that means actually you conceive, got pregnant, ovulated on day 18, which is 14 days before your next period would’ve come. So there’s always going to be a little bit of difference between how old your baby really is and the due date that we give you.
Sunny Gault: So this is an estimate really, right?
Lali Reddy: Exactly.
Sunny Gault: Ok. So what factors go into determining, or estimating basically, this due date? What do you consider?
Lali Reddy: Well, there are several different things that go into play. The earlier you go in for your prenatal visit, the easier that we are able to establish what your due date is. Keep in mind that you further along you have your ultrasound, the greater the margin of error. So in other words if you have your ultrasound done at 7 weeks, the margin of error is at about maybe 5 days. If you have your ultrasound done at 16 weeks, the margin of error can be a week, maybe even 10 days. If you have your ultrasound done at 20 weeks, the margin of error can be +/- 10 to 12 weeks. And at 36 weeks, it can be up to +/- 3 or 4 weeks. So basically what the margin of error is you can have 10 doctors do an ultrasound on you, the same day, within a few hours and they can come up with 10 different results within that range that we call a margin of error. So we would never change your due date based on a later ultrasound, but if you come in early, let’s say at 7 weeks, and the ultrasound says that no, you are actually at 10 weeks, we would change your due date, so we would base it on the ultrasound. But let’s say your due date calculated on your last menstrual cycle, by your last menstrual period, puts you at 7 days and 3 weeks and my ultrasound says you’re 7 days, we wouldn’t change it on that basis because it’s within the margin of error. So we would give you a due date based on the first day of your last menstrual period, we would add 30 weeks from there and that would give you your due date.
Sunny Gault: So when you say the ultrasound says what are you looking at within the ultrasound to determine due date?
Lali Reddy: The very fixed measurements that we do internationally, just about everywhere we use these same measurements, under about 12 to 13 weeks we use something called “the crown-rump measurement. We put the arrow on top of your baby’s head and we put the second arrow at the very tip of your baby’s bottom and we do a measurement. Based on several thousands of previous measurements, your ultrasound has computer to calculate it how far along you are based on that particular measurement.
Sunny Gault: But can’t your baby just be a small baby at that age, or not really?
Lali Reddy: Not at that time. There is a term called “small for gestational age”, or a “large for gestation age”, but these things don’t become apparent until much later in pregnancy. There are going to be normal genetic variations, if you’re 4 feet 11 inches, weigh 120 pounds, your husband is 5-6, you don’t really expect to have a 10 pound baby, though that can happen. So generally speaking the measurements that are done earlier in pregnancy tend to be very accurate. After 12 weeks we do certain other measurements, especially in the 2nd and 3rd trimester. We measure something called the “biparietal diameter”, the BPD, which is the measurement of the diameter of your baby’s head. We use another measurement for the head circumference. We use a 3rd measurement called the “abdominal circumference”, just the periphery of your baby’s belly. The 4th measurement that we use is the femur length, the measurement of your baby’s thigh bone. So with this the computer and the ultrasound machine is able to calculate exactly how far along the baby is. It’s also able to estimate the growth of the baby, that there’s no discrepancy between the head measurement and the abdominal measurement, that all the measurements are tilling very precisely and that the baby is growing appropriately from one ultrasound to the next.
Sunny Gault: But at that point you’re not really looking to verify due date, are you? You’re looking more at the baby itself, to make sure that the baby is growing appropriately.
Lali Reddy: Exactly. We do have patients that come in much later in their pregnancy for their first visits…
Sunny Gault: Really?
Lali Reddy: Oh, you’d be surprised. I have people that come in like a month before, a couple of month before, and it does not necessarily mean that they’re not carrying ore careless. There are financial circumstances. Some people don’t know that they are pregnant until much further along. It always sounds surprising to me, any woman who’s felt a baby kick, how can they not know?
Sunny Gault: But maybe it’s their first pregnancy, they never felt a baby kick before, there are other factors.
Lali Reddy: So when they do come in later in pregnancy they have no clue about their last menstrual period, then we pretty much have to go along with what the ultrasound says.
Sunny Gault: So let’s talk about that pregnancy wheel, that due date that we’ve all seen our providers pull out and kind of look at. What is on the wheel? In your personal opinion is that a good measure, at last in the beginning part of the pregnancy, before these other measurements are available? Is that a good way to help determine due date?
Lali Reddy: Absolutely, it’s very, very accurate. There’s just a bunch of lines over there. It’s a wheel within a wheel. You put the date of your last menstrual period to coincide with the mark on the wheel that says “last menstrual period”, you look for the number 40 and you see what date it falls on. But quite honestly and easier way to do that is if you’re just doing it mentally, if you don’t have access to the 2 dozens apps there are. If you just want to do it mentally, the best way to do it is minus 3 months and add 7 days. So let’s say that your last menstrual period was the 15th of November, you subtract 3 months from there and that will give you 8. 11-3=8, which is the month of August; then you add seven days, so the due date will be the 22nd of August.
Sunny Gault: That is interesting, I’ve never heard of that before.
Lali Reddy: It’s a very simple way of doing it, so that you don’t have to have access to all these other things.
Sunny Gault: Yes, I do have to say that with my little boys both were given a due date and my first baby came 3 days after, so just 3 days after the due date, and my second one a c-section, so it’s kind of hard to say when he would’ve come, so I don’t know how accurate that due date was. But I did put a lot more emphasis on due date with my second because I felt “If we are specifically taking a baby early’, and I think a lot of mothers have that kind of concern too. If you are going to have something schedule, whether it’s surgery or whatever, we really got to know how old these babies are going to be. Same thing with me now, with twins. We know these twins are going to be born via c-section. So before we take them at 36-37 weeks, we better know that that really is the week. Do you find, doctor Reddy, that more and more of your patients are focused on their due date then when they know that there’s sort of c-section or surgery that’s pending?
Lali Reddy: Absolutely, and it cuts both ways. In my practice I really do try to avoid elective inductions unless there’s a true medical reason for it. Having said that, I do have patients whose husbands are in the military, who really need to be delivered by a specific time; I have patients who live way out in Pine Valley and it’s their 4th baby…
Sunny Gault: And they don’t know when it’s going to come.
Lali Reddy: … terrified that they are going to have the baby in the car…
Sunny Gault: Precipitate labor…
Lali Reddy: … so we do schedule them for inductions. It’s very, very important to know the due date when you’re scheduling something electively, whether it’s a c-section or an induction. There’s now a national consensus that you really should do inductions or c-sections. Let me backtrack: you shouldn’t do inductions, but prior to 39 weeks. Until now, we were fairly cavalier, we used to think “Oh, after 37 weeks the baby is essentially mature, what’s the big deal?” But there’ve been some very good studies that show that even a day before39 weeks the baby still has a chance of developing respiratory distress syndrome, which it was not a very good thing. The baby ends up being in an incubi, has a lot of problems. It’s not just breathing issues, there are a lot of other interconnected issues when the baby has respiratory distress syndrome. We generally don’t do inductions at all before 39 weeks, in fact even if a tried to the hospital wouldn’t let me, unless I can justify the reason for the induction.
Sunny Gault: That’s a hospital policy.
Lali Reddy: It’s not an individual hospital policy, it’s now a national consensus, and so most hospitals will toe the line. It’s a recommendation by my college, the American College of OB/GYN now that that is how it really should be done, if you’re doing the right thing for your patient. Talking about c-sections, we have found that doing a c-section between 38 and 39 weeks for twins is better than waiting past 39 weeks. There’s a little bit of an exception for that, because the physiology of twin pregnancies is different, twins grow at a different rate, the placenta may age differently and so on. But for vaginal delivery, for induction, we really do want to wait until 39 weeks.
Sunny Gault: Let’s talk a little bit about what’s happening to the baby, how they’re growing between weeks 47 and beyond. Because I think that’s important too. You were talking about the lungs and everything kind of maturing, so what’s happening to the baby during 37 and 40 weeks?
Lali Reddy: Around 37, 38 weeks, the baby is essentially fully mature, except for the lungs, mostly the lungs. There is something called a surfactant, which helps keep the little air sacks in the lungs open. Without the surfactant, the sacks will stick together, so there is not going to be enough exchange of oxygen. You could actually force oxygen into the baby’s lungs, but it’s really not going to defuse into the baby’s blood stream unless these sacks are open to be able to convey the oxygen. So even at 37 weeks, even at 38 weeks, 38 weeks 5 days, 6 days, there can still be a problem with these sacks being open, so up to 5% of babies, even at 37 and 38 weeks, these surfactants are still developing. But other than that, the baby is essentially mature, other than this factor. Between 39 to 40 weeks the baby is considered fully formed and fully mature. Between 40 and 41 weeks, however, a lot of changes start to take place. The baby’s getting bigger, so the later you go, the later you risk ending up with a c-section, because the baby might be too big for you to deliver. There’s a condition called shoulder dystocia where the head can get out, but the shoulders get stuck. Obviously that doesn’t happen with every baby that’s larger, that’s older than 40 weeks, but there is a small risk of this happening. Also around this time, the placenta starts to get old. There’s calcification in the placenta, the blood vessels are not quite as strong, so there’s not an appropriate exchange of oxygen and nutrition to the baby. So the baby slowly starts to outstrip its blood supply from the placenta, and can actually shrink and lose weight and develop all kinds of problems with breathing and with low blood sugar and so on the later you pass the due date, so many of us prefer to perform an induction between 40 to 41 weeks, generally at 41 weeks. There’s nothing really wrong with waiting up to 42 weeks, though statistically there is a higher instance of morbidity and mortality between 41 and 42 weeks. It’s about twice as much if the baby was born under 41 weeks. After 42 weeks the morbidity and the mortality is almost 2 to 7 fold, depending on the studies that you look at. So you really don’t want to go much beyond 42 weeks at all. We generally recommend 41 to 41 ½ weeks. Even inductions at 40 weeks I personally don’t recommend them unless your cervix is ripe, unless your cervix is ready. There’s something called the bishop score out of ten, if you’re less than 4, the chances of having a successful vaginal delivery don’t look really good. The bishop score is based on how thinned out your cervix is, how dilate it is the position, whether it’s very posterior or it’s moving forward. It’s probably a good idea to have a good bishop score if you want to be induced prior to 41 weeks. After 40 weeks we like to monitor the baby’s heart rate, to make sure that the placenta is working appropriately. If you do go over due, it’s important for us to know that, so we could monitor the baby twice a week to ascertain its well being.
Sunny Gault: That’s really interesting. I definitely want to go into this “what happens after 40 weeks”. I want to take a quick break and when we come back we’ll explore this a little bit more. We’ll be right back.
Sunny Gault: Welcome back everyone. Today we’re discussing the importance of due date. Doctor Lali Reddy is an OB/GYN with Sharp Grossmont Hospital and she is our special expert joining us here in the studio. doctor Reddy I do want to talk more about going past your due date, we were talking about that before the break. I think that’s what most moms are concerned about when we talk about an induction that we are taking a baby who seems to be perfectly fine if all test results show that, that is it ready to come out yet. I know here in the San Diego birthing community we’re really focused on letting the baby do what it’s supposed to do. Too much medical intervention just seems not quite right to a lot of people. Honestly, I’m one of those people too. I would like to do things as “normal” as possible, the way God intended it to be. I think that’s the big concern, and when you talk about induction, unless there’s a problem, because there could be a problem, and you definitely want to do what’s best for you and your baby. But just because you go past 40 weeks there’s kind of this stigma “Oh, they want to induce me cause I’m past 40 weeks, but there’s no other signs that that can be an issue”. I know with my first born I actually had a prenatal appointment on my due date, and on my due date they scheduled me for an induction for a week later, just in case. I was not ok with that, but I didn’t fight it because my body knows what it’s doing, I’m going to go into labor before that. But it bothered me, I was perfectly healthy pregnancy, no problems whatsoever and we didn’t know there were going to be any complications with the birth, so it wasn’t about that.
Lali Reddy: You are your best advocate. If someone, your physician, suggests something to you that you’re not comfortable with, you really need to find questions and find out the reason. Most physicians are very reasonable. If there’s something that’s making you unhappy, you’re uncomfortable with it, no one is going to force you into the hospital and tie you down and induce you.
Sunny Gault: Yes, they can’t, like no one can tell you that you have to have a c-section. Even though they can recommend it, no one can make you do anything you don’t want to do.
Lali Reddy: Exactly. It’s illegal; it’s called battery if I force my patient to have a c-section, for instance. So, as I have mentioned earlier, elective inductions prior to 40, 41 weeks, you really have to put a lot of thought into it, if it’s not for a medical reason. After 40 weeks, I know I’ve heard you say this phrase many times in the last few minutes, that baby’s come when they’re ready, when they want to, and that is a little bit of a euphemism, because some babies just don’t know when they’re ready.
Sunny Gault: Sometimes things happen.
Lali Reddy: Sure. I have many of my patients who refuse to take as much of… they won’t even take a tablet of Tylenol, they won’t drink a cup of tea, because they’re so concerned about their babies wellbeing. Yet these same patients are being cavalier about disregarding well founded medical science. If your baby is twice as likely to have bad things happen to it why would you risk it? So there has to be some rationality to your decisions, rather than broad statements like “babies know when they come”. In most cases that is true, and really child birth is natural up to a point. 99 times out of 100 you can have your baby at home, without anything happening to it. You go to the hospital just to prepare for the eventuality that something could go wrong, but this isn’t fearmongery. You can have a perfectly good experience in the hospital if you know your rights, if you know what you want, you’ve discussed your birth plan with your physician before and he or she points out what’s perfectly acceptable, what’s middle of the road and what’s really a big no-no, so both of you are on the same page. Ehen you do go into the hospital, you should have a positive attitude that people who are helping you, who are with you, are your advocates, they’re not your adversaries and you have the final say in every matter. When you do form an opinion about anything to do with child birth, you want to make sure that you get your information from respected sources, like webmd, emedicine, mailclinic, actually has a great website on pregnancy, the American College of OB/GYN, these are all very neutral sources, but you can get the foundation of your facts and then develop up your opinions after that. A lot of what you hear from family and friends, however well meaning they are, may just be hear-say. You want to make sure that you base your fact on established science and then ask questions from there, whether it’s applicable to your situation.
Sunny Gault: I think the last comment that I would make is that, we’ve been talking about this communication; I think that’s so important between patient and doctor, whoever your care provider is, whether you’re seeing a midwife, in addition to... whoever that is. I think the big advocate should be that women could give birth the way they want to, to give birth, assuming that everything is ok with the pregnancy and the baby and everything. I like to think that the doctors are there to support you and encourage you and be your advocate. But at the same time is good to do your own research and ask questions. It doesn’t mean that your research is right, it doesn’t mean that anyone is necessarily right. You’re both trying to have the best birth experience possible. They want you to have a healthy baby and a great labor and delivery experience. I think it’s just about communicating that to one another. You don’t want to have an induction, talk to them about what are your reasons. I doubt they are going to say it’s a golf game. If they do, find another provider, please. I don’t think it’s that black and white.
Lali Reddy: Just keep in mind that inductions never run on schedule. You can deliver 6 hours after the induction, 48 hours, so honestly there’s no way for a physician to plan their schedule around an induction.
Sunny Gault: It’s a misconception. Well, doctor Reddy thank you so much for being here today and taking to us about the importance of due dates, providing some perspective for women out there This conversation is actually going to continue for members of our Preggie Pals club. After the show we’ll discuss how the prenatal care could change if you do go past your due date and you still haven’t delivered that baby of yours. So will be right back.
[Theme music][Featured Segment: From our Listeners]
Sunny Gault: We have a comment from one of our listeners, it comes from Jamie: “Hi, Preggie Pals, I’ve been using your apps for the past few weeks and I travel a lot so I don’t always get a strong internet signal. Is there a way to download the episodes to my app, so I don’t have to worry about my connection?” Yes, Jamie, absolutely. If you are in the app, I’m actually using the iPhone app, go to the episodes page where you can see all of the episodes, and you’ll see there’s a faint star next to each episode. If you tap on that, that star’s going to turn yellow. When you do that you’re going to see this yellow circle form around the star. That means it’s in the process of downloading it to your app. Once that process is done, the episode is on your app, everything is fully highlighted, the star, the circle around it, that’s how you know you have that episode on your phone. It’s not going anywhere and regardless to your internet connection you’ll be able to listen to that episode. Jamie thank you so much for your question.
Sunny Gault: That wraps out our show for today. We appreciate you listening to Preggie Pals. Don’t forget to check out our sister show Parent Savior, for parents with newborns, infants and toddlers, and our show the Boob Group for mother that breast feed their baby. This is Preggie Pals, your pregnancy, your way.
This has been a New Mommy Media production. Information and material contained in this episode are presented for educational purposes only. Statements and opinions expressed in this episode are not necessarily those of New Mommy Media and should not be considered facts. Though information in which areas are related to be accurate, it is not intended to replace or substitute for professional, Medical or advisor care and should not be used for diagnosing or treating health care problem or disease or prescribing any medications. If you have questions or concerns regarding your physical or mental health or the health of your baby, please seek assistance from a qualified health care provider.
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