Class 12 Biology (India)
Created by Vishal Punwani.
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- If I were a healthcare professional I would reccomend the all fours position or standing up for a breech vaginal birth since that opens the birth canal past 10 cm.
However most people despite being told that vaginal birth is very much possible with the breech position and with multiples do a C section anyway. Why is this?(8 votes)
- You are correct that a breech presentation can often be delivered vaginally. However, the possibility of health complications to the baby (hypoxia, mental retardation, or even death) and the mother (tearing of the birth canal, excessive bleeding, or even death) as well as potential expensive malpractice lawsuits against the health care provider make the C-Section a wonderful alternative to a complicated vaginal delivery. As explained in the video, it's all about assessing "benefits vs risks". Hope this helps. Good Luck.(22 votes)
- At around1:29, he said that that "...These contractions can either be called false labor contractions or Braxton Hicks contractions..."
Where does the name "Braxton Hicks" come from? Is there a reason that they are called that?
Thank you in advance for any answers!(4 votes)
- John Braxton Hicks was a British obstetrician. In the late 19th century, he described these types of contractions that didn't result in labor. They were named after him.(5 votes)
- I have heard that for the average woman, during each successive pregnancy the pain gets stronger and during each successive birth it gets milder so that the pregnancy pain to labor pain ratio increases. Is this because the uterus after it shrinks is still larger than its prepregnancy size and so during the next pregnancy it stretches more causing more pain and a higher risk of uterine rupture and during labor, because it is stretched more it doesn't have to contract as hard?(6 votes)
- Why is there an increase in oxytocin? Does it have to do with the really high levels of estrogen or with the drop in progesterone or both?(2 votes)
- it is considered as part of a reflex in response to cervical dilation. this is sensed by the somatic nerves and the pituitary responds by secreting oxytocin.(4 votes)
- Where are you getting 38.5 weeks for full term? Even ACOG states Full Term is 39 weeks 0 days to 40 weeks 6 days. http://www.acog.org/About-ACOG/News-Room/News-Releases/2013/Ob-Gyns-Redefine-Meaning-of-Term-Pregnancy
Thus the classic 40 weeks is full term... Perhaps with all of the inductions we see 38.5 weeks.(2 votes)
- It's the difference between calculating the number of weeks from the last menstrual period (+/- 40 weeks) or the estimated ovulation (+/- 38 weeks). There due date is always an estimate an can be affected by various factors such as differences in cycle length, and whether it's a woman's first pregnancy (interestingly, first borns are more likely to be born after 41 weeks than second- or third-borns, and at the same time more likely to be born early, before 37 weeks. Source: http://www.livescience.com/38179-royal-baby-firstborns-late.html )(2 votes)
- At about0:55, the video stated that at week 37 progesterone levels drop down due to the increase of estrogen. In some cases, mothers were given something to make contractions happen so the baby could be delivered. Is there any way that that medication made the Estrogen levels shoot up quickly? I was just curious.(2 votes)
- The drug that is usually used to induce contractions is called oxytocin. Estrogen is usually increased in the proliferative phase of the menstrual cycle, but that cycle is “on hold” during pregnancy. I don’t think that giving oxytocin would directly cause a significant increase in estrogen release.(2 votes)
- I don't know if practice is different in the US from the UK (I am a midwife) - but we would never force restitution (the turning of the babies head) as lack of restitution is a sign of the shoulders not hitting the pelvic floor and could also be indicative of shoulder dystocia. I was hoping more for how the pelvic floor works, to help my student understand. But found this video very useful. Thanks!(2 votes)
- what is the follicle phase of menstrual cycle(1 vote)
- It is the phase in which the follice is developing and getting ready to release an egg in 14th day - ovulation(3 votes)
- Hey, great job guys. I was just wondering what causes the placenta to reduce the amount of progesteone it has been producing. Is it the increased size of the baby, compression of the uterus? Knowing this would help knowing why some mothers carry pregnancies up to 40 or 41 weeks.(2 votes)
- No one knows why or what causes this. If it occurs and is diagnosed, progesterone is available as a treatment.(1 vote)
- At around3:20you say that relaxin plays a role in loosing ligaments and symphysis pubis. I'm reading that according to some studies this is not entirely true. There is indeed this increased peripheral joint laxity, but apparently it does not correlate that much with relaxin levels.
What do you think about that?(2 votes)
- When a pregnancy has reached its full term, usually about 38-1/2 weeks, it's time for the baby to be born. Childbirth, also known as parturition, typically occurs within about a week of a mother's due date. So as the pregnancy's been progressing toward the due date, a number of physiological changes have been happening in mom to prepare her to give birth to her baby. For example, progesterone levels start to drop off a bit by about week 37. Progesterone levels were previously pretty high, because having a lot of progesterone around relaxes the smooth muscle of the uterus, preventing it from contracting and trying to expel the baby before its due date. So the level of progesterone starts to drop at about week 37, but the level of estrogen stays pretty high, and the new higher ratio of estrogen to progesterone kind of causes the uterine muscle to be more sensitive to other hormones, like oxytocin from the posterior pituitary gland that try to stimulate uterine contractions. And actually, some women feel sort of weak contractions in late pregnancy, due to the decreased levels of progesterone. It doesn't mean she's actually in labor, though. The baby isn't quite ready to be born. These contractions are just because of the decreased levels of progesterone, and they're actually given one of two special names. These contractions can either be called false labor contractions or Braxton Hicks contractions. So let's look at an anterior view of mom's pelvis and her uterus. So this here is the uterus. Here's the placenta inside. This orange structure here, that thin sort of membrane, is the amniotic sac or membrane. Now this part here, this part is supposed to be the cervix, and normally it would be more constricted, closer together, sort of like this, but I've retracted these little bits here just to give you a better view of what everything looks like. This bone here and this bone here on the other side, these are the two sides of the hip bones or the pelvic bone. So together you call the two sides of the pelvic bones the pelvis. This here is one of mom's thigh bones or her femurs, and this here, this space, is called the birth canal or the vaginal canal. So when mom reaches full term, the fetus starts to drop lower in her uterus because it's getting heavier, and when it starts to make contact with and push on the cervix here from the inside, that stimulates both uterine contractions and cervical dilation and effacement or thinning. So let's create a little mechanism here in the corner that we'll continue to work on as we go. By the way, the placenta starts to secrete higher levels of another hormone, which we haven't actually talked about before, called relaxin. This is one of those hormones that's definitely been named according to what it does. Relaxin does two things to do with pelvic bones. It loosens up some of the pelvic ligaments, so that the pelvic bones can come apart a little bit to support the enlarging uterus. But maybe a bit more importantly, it opens up the pelvic outlet by loosening the pubic symphysis joint between the left and right sides of the pelvis, and these relaxation events are important for two main reasons. One, to accommodate the growing fetus a bit better, and two, to make it a little easier for the baby to be born through that pelvic outlet, because it's a little wider now. Relaxin actually helps the childbirth process even more than this, though. It also helps to dilate the cervix during labor, and we'll see that soon. So now that we have an idea of what's happening in mom's body just before labor, let's look at the actual stages of labor, and there's three main stages. There's cervical dilation, expulsion of the baby and the afterbirth, and in total, labor can take anywhere from seven to 20 hours, depending on how quickly each stage progresses. So in labor now, and this is a sagittal section of mom, so that you can see what's going on inside. So we're in the first stage now, the cervical dilation stage, and we can see that this cervix here is probably going to get in the way of the birthing process, and it turns out that for a vaginal birth to take place, the cervix needs to dilate fully, typically to about 10 centimeters in diameter, which is enough so that the baby's head and body can sort of squeeze through. So we need that cervix to dilate. And how are we going to do that? Well, a few different ways. So first, at this point we've got a pretty high concentration of oxytocin being released from the posterior pituitary, and that's causing uterine contractions, and these strong contractions cause membranes surrounding the fetus to release other hormones called prostaglandins that soften up the cervix and actually cause more uterine contractions. So what ends up happening here, as you might imagine, is that we have strong uterine contractions that are causing the release of prostaglandins that cause even stronger contractions, and when those stronger contractions happen, more prostaglandins get released, and this cycle sort of continues a positive feedback loop, and the contractions will just get stronger and stronger as part of the birthing process, called true labor, as opposed to the false labor that I mentioned earlier. And we're supposed to be talking about how the cervix dilates, but here we are talking about contraction of the uterus, but they're actually related. So the uterus actually contracts in an interesting way. The sides contract upward, which, as you can imagine, pulls the cervix thinner and causes it to open up a bit. The contractions also push the fetus against the cervix, which is sort of a trigger that causes it to dilate even more, like we already have on our mechanism. Finally, that hormone relaxin comes into play here, dilating the cervix even more. So let's add all this stuff to our mechanism. So as the cervix dilates, this bit of mucus, called the mucus plug, that was stuck at the opening of the cervix to seal it up during pregnancy, that kind of comes out and gets discharged out of the vagina, and this can actually happen anywhere from a couple days before true labor to during labor, and it usually serves as a sign that labor is progressing. Also there's this membranous sac that surrounds the fetus, called the amniotic sac, and that'll rupture during labor and release its amniotic fluid. And that's what we always hear of being referred to as, mom's water breaking, and I've drawn it here in this orange color. So back to the cervix. Once it dilates to about four centimeters, mom's body moves into a phase called active labor, where her contractions become stronger and closer together, and once the cervix gets dilated to about 10 centimeters, its maximum diameter, mom starts to get the urge to push, and this signals the start of the second overall phase of labor, the expulsion phase. So the expulsion phase starts when the fetal head enters the birth canal and ends with the birth of the newborn. During the expulsion phase, the uterus continues to rhythmically contract to help push the baby out of the mother's body. Now, you might be thinking the birth canal might be a little small for the baby's head. Aren't we worried about that? Well, it turns out that the skull bones of the newborn haven't really fused together yet. So, they sort of slide over top of each other a bit and sort of compress the skull enough so that the baby can make it through the birth canal. Once the baby's head crowns, or becomes visible to the healthcare professional assisting with the birth, they'll turn the baby to the side, to make delivery of the rest of the baby's body a little bit easier on both the mother and the baby. By the way, in this drawing here, this baby's a little past crowning. Once the baby is out, the umbilical cord that connected the baby's belly button or umbilicus to the placenta gets cut, and the baby gets cleaned up. The final step of labor is the delivery of the placenta and its associated membranes, collectively called the afterbirth. Once the baby's delivered, the uterus continues to contract, and in doing so it sort of causes the placenta to detach from the walls of the uterus and eject out of the vagina, and this actually happens pretty easily, compared to the birth of the baby, or so I'm told. The uterus actually continues to contract after this happens, though, and that helps the uterus to return to its pregestation size. And this process of uterine shrinkage almost is called involution. This involution also allows mom's other abdominal organs to return to their normal locations after pregnancy. I should also mention that most of the time the baby's head comes out of the cervix first, an orientation called the vertex presentation. In less than 5% of births, though, the baby's oriented the other way around, with its gluteal region or its legs set to come out of the cervix first. This orientation is called a breech presentation and carries more risks to both the mother and the baby than a normal vertex presentation during birthing. So if this ends up being the case, the healthcare team will likely want to proceed with the birthing process via a birthing procedure called a Cesarean section or a C-section. This involves making incisions in the lower abdomen and uterus to deliver the baby that way, directly through the anterior abdominopelvic wall. C-sections are slightly riskier than normal vaginal births, in terms of risks to both mother and baby. So the healthcare team will usually only recommend a C-section when the benefits outweigh the risks.