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Video transcript

let's start out with some definitions so preterm labor refers to delivery that occurs too early and by that we mean before 37 completed weeks of pregnancy so delivery that occurs before 37 completed weeks of pregnancy in a normal term pregnancy right so full-term pregnancy is anywhere from 37 to 41 weeks long and so preterm is anything short of 37 to 41 weeks and I want to highlight that this is a really important topic to discuss because preterm birth is the number one cause the number one cause of neonatal mortality so so it's the leading cause of death in the first 28 days of the baby's life and really even in those babies who do survive they're at risk of developing long term issues so neurodevelopmental deficits for example jumps out to the forefront of the mind such as cerebral palsy impaired learning visual issues so it's a really big issue and you can probably imagine the risk of death and the risk of these complications decreases the further along the pregnancy is at the time of birth so a 36 week old premature baby will probably fare better the 30 week old premature baby for example and with the same token a higher birth weight in a premature baby is also associated with less complications with a better outcome so what causes preterm labor to occur I mean the pregnant body knows that the baby needs to be kept inside for 37 to 41 weeks so why would it initiate labor earlier than that well we kind of break up the causes of preterm labor into four groups so four four major causes the first major cause is stress whether that's major physical stress or psychological stress such as with anxiety or depression and there's thought that the stress whether the physical stress or the psychological stress activates the HPA so the stress activates the HPA axis which stands for the hypothalamic-pituitary-adrenal axis in the mom and this is this long named axis is basically the stress axis of the body and when it's activated stress hormones get released so when the HPA axis is activated the stress hormones get released and the stress hormones are will initiate the preterm labor and this idea that stress can actually induce premature labor has been validated it's actually been shown that women who have symptoms of depression for example have twice the risk of going into preterm labor compared to women who don't have those symptoms and really the same stands true for the opposite side of things for the other side of things so if the fetus experiences any stress it's associated with an even higher risk of preterm labor so in this case we're talking about stresses such as damage to the fetal blood vessels or or improper formation of the blood vessels in the placenta like what you see with preeclampsia so when we're talking about fetal stress we're talking about issues that reduce the oxygen nutrient delivery to the baby that induce stress in the baby all right so this is the first mechanism of preterm labor so stress induced preterm labor the second major cause of preterm labor is inflammation which can be the result of some inflammatory condition certainly or inflammation from infection so so anything ranging from urinary tract infections to dental infections or infections of the actual fetal membranes these are all things that can lead to preterm labor and in addition to causing inflammation bacteria can actually cause preterm labor through another mechanism where they create several different enzymes that can actually degrade they can actually break down the fetal membranes which can induce labor so inflammation whether it's through an inflammatory condition or through infection can cause preterm labor now the third major cause of preterm labor leads to placental abruption placental abruption which is when you have bleeding that occurs between the placenta and the uterine wall because of some pathology some irregularity that makes the uterine blood vessels more fragile and more prone to rupture and it kind of makes sense how this would lead to preterm labor because in response to this bleeding that's occurring between the placenta and the uterine wall the uterus does what it knows best it starts to contract because this contraction of the uterus squeezes down and clamps down on the blood vessels that are traveling through the wall of the uterus so great that slows down the bleeding but of course a side effect of all of that contraction is the induction of Labor so that's how you get preterm labor with placental abruption and finally the last major cause of preterm labor is is an abnormality some abnormality in uterine distension so the uterus is more distended than it normally would be at that point in the pregnancy and that stretching of the uterus that stretching of the myometrium of the uterus a muscular layer of the uterus sort of tricks the body into thinking that the pregnancy is further along than it actually is and a couple of things that could cause the uterus to be more distended than usual include include multiple gestation so having twins triplets quadruplets etc or or polyhydramnios so polyhydramnios is another thing that can lead to I can lead to uterine distension and polyhydramnios refers to when there's too much amniotic fluid so that could also do it and I guess in this category you could also talk about abnormalities with the cervix so so the cervix can be too dilated or too effaced so too thin in the absence of labor and we refer to that as cervical insufficiency cervical cervical in insufficiency so basically that the cervix is instinct shut making it more likely for preterm were to occur okay so how do we diagnose preterm labor well you start off by looking for signs and symptoms of labor right regular labor such as uterine contractions now remember that irregular uterine contractions occur at all stages of pregnancy they're called Braxton Hicks contractions or sometimes they're called practice contractions right and they occur all throughout pregnancy so it's really important to distinguish those Braxton Hicks contractions so those practice contractions from true labor contractions and in labor what we're looking for is contractions that are more that are more regular more frequent and more intense and those uterine contractions have to be accompanied by cervical change so the cervix has to become more faced so more thinned out and it has to become more dilated so it has to spread apart and we assess for that cervical change by doing a speculum exam so we insert a speculum through the vagina and look inside and also while we're looking inside we also look for cervical and we also while we're looking for cervical change we also look to see whether the fetal membranes are intact or whether they ruptured because if the fetal membranes have ruptured which is commonly referred to as the water breaking or the water bag breaking it's more likely that the woman is in true labor rather than in false labor now in women who are less than 34 weeks along in their pregnancy in whom we're really uncertain of whether they're in labor or not we tend to get a transvaginal ultrasound so it's an transvaginal ultrasound is when you take an ultrasound probe it's a long probe and you insert it through the vagina so you can get a really good picture of what's going on at the level of the cervix and and the rest of the uterus and we do the transvaginal ultrasound to determine what the cervical length is so we want to see how long the cervix is because a short cervix a short cervical length before 32 weeks into pregnancy is a really good predictor for preterm labor so having a short cervix before 32 weeks into the pregnancy is a really good predictor a preterm labor and of course ultrasound gives us lots of other information like whether there are any maternal or fetal and atomic abnormalities it can it can tell us the position of the fetus if there's enough amniotic fluid it also allows us to estimate what the fetal weight is and of all this information is critical in determining the potential outcomes of the preterm birth and it helps us to sort of counsel the parents on what the potential outcomes can be all right so the next step after confirming that the mom is in preterm labor is to manage it so in all women who are less than thirty four weeks into their pregnancy the very first step is always to administer a dose of steroids usually betamethasone so beta betamethasone betamethasone is a type of steroid right and the administration of of one dose of betamethasone has been consistently shown to reduce fetal mortality and complications from the preterm birth and along with that betamethasone the mom also receives a toko lytic agent so she'll also get a toko lytic agent which is an agent it's a medication that relaxes the year so attempts to delay the delivery and we give the toko lytic agents for up to 48 hours with the hope that we can delay the delivery until the steroids have had a chance to take effect now in addition in women who are delivering even earlier on so before 32 weeks anywhere from 24 to 32 weeks into their pregnancy we also give a dose of magnesium sulfate so in addition everything else we give a dose of magnesium sulfate which has a protective effect on the brain of the fetus so it helps to prevent cerebral palsy and other neurologic issues that tend to occur in in severely premature babies so I guess that leaves us with is there anything you can do to prevent preterm labor and the answer is perhaps so the number one risk factor for preterm labor is having a history of preterm labor in a previous pregnancy and in these women who are really high risk right so if they've had a history of a preterm pregnancy there is a good body of evidence to support the use of progesterone supplements throughout the pregnancy so giving it to them throughout the pregnancy to reduce the risk of preterm labor and while there are several several things that put a woman at risk for going into preterm labor there are a couple of modifiable risk factors so risk factors sort of in the control of the woman that she can eliminate to reduce the risk of preterm labor so things such as cigarette smoking cocaine use right so avoiding those substances can also help to reduce the risk of preterm labor