- [Voiceover] 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.
And a normal term pregnancy, right,
so, a full term pregnancy is anywhere
from 37 to 41 weeks long.
And so, preterm is anything short of 37 to 41 weeks.
And I wanna 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, 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 fair better than a 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 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 axis.
So, the stress activates the HPA axis,
which stands for the hypothalamic-pituitary-adrenal axis
in the mom.
And 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 what 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 woman 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 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.
Alright.
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, 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
relates 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 though 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 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,
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 can cause the uterus
to be more distended than usual
include multiple gestation, so, having twins,
triplets, quadruplets, et cetera,
or polyhydramnios.
So, polyhydramnios is another thing
that can lead to uterine distension,
and polyhydramnios refers to when
there's too much amniotic fluid.
So, that can also do it.
And I guess in this category, you could also
talk about abnormalities with the cervix.
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 insufficiency.
So, basically, that the cervix isn't staying shut,
making it more likely for preterm labor 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 regular,
more frequent, and more intense.
And those uterine contractions have
to be accompanied by cervical change.
So, the cervix has to become more effaced.
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, 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, and whom were really uncertain
of whether they're in labor or not,
we tend to get a transvaginal ultrasound.
So, a 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 the rest of the uterus.
And we do the transvaginal ultrasound
to determine what the cervical length is,
so, we wanna 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 of preterm labor.
And, of course, the ultrasound gives us
lots of other information like whether there are any
maternal or fetal, and atomic abnormalities,
it can tell us the position of the fetus,
if there's enough amniotic fluid,
and it also allows us to estimate what the fetal weight is.
And 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.
Alright, so, the next step after confirming
that the mom is preterm labor is to manage it.
So, in all women who are less than 34 weeks
into their pregnancy, the very first step
is always to administer a dose of steroids.
Usually betamethasone.
So, betamethasone.
Betamethasone is a type of steroid, right?
And the administration 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 tocolytic agent.
So, she'll also get a tocolytic agent,
which is an agent, it's a medication
that relaxes the uterus, so,
it attempts to delay the delivery.
And we give the it tocolytic 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 between 24 to 32 weeks into their pregnancy,
we also give a dose of magnesium sulfate.
So, in addition to 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 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 at really high risk,
right, so, if they've had a history of a preterm pregnancy,
there's 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 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.