胎盘前置

so we all have that friend that one friend who's never in the right place at the right time well it turns out that placentas also have that one friend so what do I mean by that well placentas are normally located in the upper part of the uterus so near this portion of the uterus called the fundus fundus and there's this condition called placenta placenta praevia placenta previa in which the placenta is abnormally positioned so instead of being found in the upper part of the uterus it's found somewhere in the lower part of the uterus kind of kind of like this near the portion of the uterus called the cervix so instead of being found in the fundus it's found near the cervix and the placenta can either partially or entirely cover up the internal opening to the cervix so this portion right here called the internal AHS or the internal opening of the cervix so what is this happen well it turns out that the placenta will form wherever the embryo implants so if instead of implanting near the top of the uterus like it's supposed to the embryo implants in the lower part of the uterus the placenta will also form in the lower part of the uterus leading to placenta previa so if you look at this diagram you might ask yourself well yeah sure the placenta is located in the wrong place but is that necessarily a bad thing and the answer to that is sometimes so early on in the course of a pregnancy if a woman is diagnosed with placenta previa it tends to not be that big of a deal and the reason for that is because as the pregnancy progresses the baby grows and as the baby grows the uterus gets larger and it stretches out and with the stretching out of the uterus the placenta gets dragged along to a higher position so if a woman is found to have placenta previa early on in the course of a pregnancy as the uterus grows the condition tends to self result and the placenta tends to find itself in a normal position by the end of the pregnancy so much so that it's pretty rare to still have the condition by the time the baby is ready to be delivered so for that reason if a woman is found to have placenta previa early on in her pregnancy it tends to not be that deal if however she's found to help listen to preview later on in the course of a pregnancy or she was found to have it earlier on and it still persists by the time that she's ready to be due it tends to be a very big deal and the reason for that is that in this location the placenta is really prone to bleeding and I want to show you why that is so I kind of want to expand this or zoom into this part of the uterus so we already talked about the structure of the placenta in another video that's called meet the placenta so over here we're just briefly gonna gloss over it so this is the uterus or or rather it's the wall of the uterus and the uterus is a muscle right it's a muscular organ so in a non pregnant woman there are all these blood vessels or arteries they're called uterine they're called uterine arteries that come down to the uterus and they supply it with oxygenated blood because again the uterus of the muscle so it needs loss of oxygen so what happens in pregnancy is that these uterine arteries become really juicy and plump and they actually cross through the wall of the uterus and they squirt out all this blood kind of like we said kind of like we said the Jets in a hot tub do and they squirt out all the blood into the placenta so the placenta is kind of like a pool of blood and the baby also sends down blood vessels into the placenta so that it can get access to all the oxygen and the nutrients from the pool of blood that is the placenta so something pretty amazing happens late in the course of the pregnancy when the baby is pretty close to being delivered so as you might know if you look at this diagram over here so as you might know when babies make their exit from the uterus they do so headfirst and their heads tend to be pretty big and you can see that this thick and plump part of the uterus the cervix is kind of standing in the way of the baby's head so what happens towards the end of the pregnancy is that the wall of the uterus over here the cervix thins out to widen the passage for the baby now normally this is a good thing it's an awesome thing but if the placenta is sitting right here like it does in placenta previa it can be a pretty dangerous thing so when the all of the uterus thins out the attachment here the attachment between the uterus and the placenta is actually strained it starts to become weakened and the placenta starts to detach and as you can imagine these uterine arteries which are actually in the wall of the uterus are being tugged on in this direction as the wall thins out but since they're also attached to the placenta they're also being tugged on in the opposite direction so pretty easily the tension on these arteries can cause them to rupture and blood leaks through into the vagina and that's actually how this condition how placenta previa tends to present with vaginal bleeding late in the course of the pregnancy and and that's called antepartum so that's called antepartum bleeding so I enter part of vaginal bleeding and antepartum refers to the portion of the pregnancy that's after the 20-week point so it turns out that there are two major causes of antepartum bleeding one of them is called placental abruption which is something that I'm going to talk about in its own dedicated committed video and the second cause is placenta previa and there's a really important way to tell them apart so placental abruption tends to present with painful bleeding whereas placenta previa tends to present with bleeding that's not so painful so painless vaginal bleeding so if a woman presents with painless and departing bleeding so painless vaginal bleeding after 20 weeks into her pregnancy she's suspected of having placenta previa and if that's suspected if placenta previa is suspected the very first thing we do is in ultrasound so we slap an ultrasound onto the belly to visualize the location of placenta and if the woman is found to have placenta previa it is really important we make a pretty big point not to do a pelvic exam so not to insert either a speculum or a finger through the vagina and that's because either of these two maneuvers inserting either speculum or a finger through the vagina can cause or it can worsen the vaginal bleeding okay so if a woman has placenta previa what's next well a lot of that depends on what she looks like once you present so if she comes in with pretty minimal vaginal bleeding and she's hemodynamically stable so if her blood pressure and her pulse are okay then she's probably gonna be sent home on bed rest and she's gonna be told to avoid strenuous physical activity and to avoid sexual intercourse because that in and of itself can cause bleeding and then she'll probably be brought back to the hospital around 34 weeks into her pregnancy to have a c-section and the reason why we choose to do a c-section rather than proceed with a vaginal delivery is pretty apparent in this diagram so remember when we said that the baby passes through headfirst so you can see that the placenta in placenta previa is blocking the baby's path and during delivery the strength of the uterus contracting and pushing on the baby through can shear the placenta which remember is a pool of blood pretty much so that can cause massive hemorrhage for the mom so that's why we offer a c-section to avoid this potentially fatal situation for the mom now if instead the mom presents with massive bleeding and she's hemodynamically unstable sit for blood pressure no pulse are not doing so okay then we go in for a c-section at that time regardless of how far along her pregnancy is or how old the baby is to prevent any consequences for the mom so I guess that leaves us with with a pretty important question a question that a lot of people tend to be interested in and that is what increases your chances of having this condition and one of the biggest risk factors I guess you can say is is having a history of placenta previa so if you had placenta previa with the previous pregnancy you're much more likely to have it with any future pregnancies and another pretty big risk factor is multiple gestation so women who have twins or triplets or quadruplets or more babies because each of these babies has its own placenta and you can imagine that the higher the number of placentas the greater the chances of having one fall into this area right so it's simply a probability game and there are a few other risk factors like having surgery on the uterus or having a uterine scar that all increases your chances of having placenta previa so there you have it placenta praevia or the placenta that's never in the right place at the right time