Human Development: Prenatal and Perinatal Periods Part I

Critical periods are a time, in this case we're going to call it prenatal time, is a period before birth, right, a window in which an organism is more or less reactive to outside influences or internal influences It's critical because that sensitivity means that there is more chance for damage prenatally during certain periods, right? More chances for what? Birth defects or what we're talking about prenatally

But there are periods after birth in people's lives that are also more or less sensitive periods You develop language in your early years, starting out by babbling, and forming syllables, and then forming words, then telegraphic speech, then you learn the rules of grammar, and then you have a symbol system now that helps you interpret reality and transmit your interpretation of reality to other people through a thing we call language Most people learn the language of the family they are born into But there's a sensitive period in early childhood where you can pick up multiple languages relatively easily So if you live in a bilingual or trilingual house, this sensitive period allows you to acquire multiple symbol systems that are languages fairly easily, but once you exit adolescence, that sensitive period passes and now it becomes relatively difficult to acquire a new symbol system, right? Anybody that's taken a foreign language for the first time in high school or later can attest to the fact that it is hard to do

But it was easy to do early in life, and that's reflecting the postnatal sensitive period versus a prenatal critical period where you can do great amounts of damage with relatively little negative influence So sometimes you have devastating effects Maternal malnutrition can be one of those things, we're talking prenatal now, that increases risk for birth defects, or birth complications, and birth complications can give you post natal effects, right, cutting off the oxygen flow for example because you have an umbilical cord wrapped around the neck, oxygen flow to the brain, right? Deprived of oxygen, brain cells die, and as I've already told you in a previous section they don't grow back You don't get new ones So you can have permanent damage from a relatively brief period of oxygen deprivation to the brain

But malnutrition means that you are not getting the vitamins and minerals that you need to sustain the growth of the single cell organism into a multi-cell organism, going from an embryo to a fetus and this is where people get into massive debates, even violent debates, over what is life, and when does it begin, and this gets into a debate about abortion, pro-life, nobody's actually pro-abortion, nobody's like kill the babys They are questioning at what what stage life becomes viable, at what stage you define it as a person, at what stage to you declare the mother's health be at risk versus the risk of the potential child that would come forth and I'm not giving you the answers because I don't have them I would suggest that nobody does because it becomes a matter of personal interpretation about what your ideas are for spirituality, god, physicality, what it's worth being born with, massive defects or none at all whether you have the ability financially or emotionally to raise a child, whether there are options to adopt out to people who have those abilities, these are really, really, really complicated issues and I would respect wherever you stand on any of those issues because it is your choice and it is your value and you should have it but you should be informed as equally as much about the other side's viewpoint To assume that they're all crazy or wrong is fundamentally what human beings do when people differ from them, right, but they're just as passionate on both sides of every argument you want to come up with and in this case, it's debatable by definition If it wasn't debatable there wouldn't be a debate, right? So keep in mind that when people oppose you, you can strengthen your own arguments if you better understand their arguments, or you might gain more compassion for the other side whatever that other side maybe on any debate if you inform yourself about how they see things, because it turns out we're all human beings prone to making pretty radical conclusions and then sticking with them, but when we're talking about this period of prenatal development it's a lot of variety

When we're going from a double cell to a single cell back to multiple cells the don't look anything like a person, to a thing that looks a lot like an alien to something that looks definitively like a person, there's a lot of room for interpretation, and there's a lot of room for problems especially in the embryonic phases The first few weeks before we get to the fetal stage you can cause a lot of problems with a little bit of damage, right? And once you get past that it doesn't mean you can't cause damage It just means that the damage caused is likely to be less intense or maybe less prolonged after birth or things of that nature So teratogens would be external environmental insults to the organism at whatever stage it's in So, substances that produce birth defects are many

You know some of them Pretty quick we can name a few, right? Mercury, lead, well those are substances that a mother might be exposed to without even realizing it that would then be crossing the placental barrier In your brain, you have blood vessels and they deliver the nutrients in and the waste products out and they have a thing called tight gap junctions In other words, the cells that make up the vessel wall are tightly packed together such that anything that goes into the brain has to pass through two cell walls, right, and that keeps many substances out of your brain, such that the substances you feel affecting your brain whether it's nicotine or caffeine, or other kinds of things, drugs of choice or of abuse,, they're able to pass the blood-brain barrier They're able to go through those vessel wall cells into the brain and have an effect Well other molecules need to get to the developing organism prenatal at all stages of gestation, right, and so you can't have that tight of a gap

You've got looser gaps between the cells and larger molecules can cross that barrier called the placental barrier It still serves as a screening mechanism, and it will screen out some kinds of molecules, but you've got to get in nutrients and you've got to get out waste products and other kinds of molecules can slip in, so anything that can affect your brain can by definition affect the unborn, right, because if it can cross the blood-brain barrier, it can most certainly pass through the placental barrier So you now have to worry about what kinds of things are going into the mother's system Teratogens is what we call them Drugs, as i've alluded to, readily cross the placental barrier because they will cross the blood-brain barrier and they can have various effects on the unborn child

Unborn child, unborn fetus, unborn embryo, however you choose to call it The organism that is in gestation, if it affects the mother, it affects that organism too In very much the same way, if one takes an amphetamine and increases the mother's heart rate it will also, assuming that the heart is developing, increase the fetus's heart rate If we look at things like narcotics, those increase chance for early death due to prematurity so these babies oftentimes are born earlier than they would be They're premature babies

That puts them at risk depending on what period of time they're born in In America and other industrialized countries we've made remarkable progress in how early a child can be born that we can keep them alive A child could be a born as early as five months gestation and through heroic medical efforts kept alive until they are viable on their own and released from the hospital Thirty years ago, they'd be dead There just wasn't an option to keep you alive

You've got to get surfactant in the lungs to inflate the lungs to be able to breathe on your own but things like respirators, and IV's, and sterile environments allow us to do some amazing things but offspring of mothers who abuse narcotics heavily are likely to be premature It doesn't guarantee they'll be premature Cocaine is just one type of amphetamine There are lots of them, right? You've heard of meth There are many types of amphetamines

We'll talk about those in a later chapter And these create a lot of defects including heart problems and brain seizures that could be fatal but they can also cause heart arrhythmias, and heart murmurs because you're now tasking that unborn heart at a rate that would be hard for an adult to take At high enough levels a cocaine use you'll die You will go into cardiac arrest It's more than your heart can bear

So imagine what it is like on the unborn, right? It's a magnified effect because the same dose is hitting them as is hitting the adult Alcohol! Alcohol abuse is probably what we're talking about here But abuse could be short term like in a giant binge of high, high doses or it could be long-term in maybe moderate doses taken in over a longer period We don't really know and it's hard to say and that's one of the problems with assessing damage quote-unquote damage because if we have these teratogens at play I don't know what development could have been All I know is what I get, and I don't know if that's a damaged set of developmental parameters or if that's normal

Depends! Sometimes with fetal alcohol syndrome, that's a severe damage that you can see at birth It includes microcephaly, a relatively small head Now you know babies, they got big old heads, don't they? And it's one of the things that makes them cute They've got that big old wobbly head on that tiny body Right? But being born with a small head is indicative of some problems, right? Relatively small head

Heart defects Irritability Hyperactivity Mental retardation Most kinds of mental retardation are actually not genetic

One you're probably familiar with would be Down Syndrome, right? It retards mental processes It's not an insult It's a clinical designation so, knowing that, I hope you will use the word a little more carefully then it is usually used in colloquial expressions When you say retarded, clinically what you mean is you have intellectual deficits, you don't have value deficits You have wonderful children who have problems with certain kinds of cognition, right? But most kinds of mental retardation are not caused by genetics

They are caused by birth defects and insults to the early born organism in very early childhood, drop on the head for example, or being exposed to lead-based paint where a kid might eat paint chips because you know what kids put in their mouth when they're tiny? Everything! So what we see is with alcohol at high quantities you can cause these problems, mental retardation Now, I point this out, back in the day, you weren't told as a mother that you shouldn't drink and that you shouldn't do drugs and you shouldn't smoke and all of these things My mom drank normally She wasn't an abuser of alcohol She was a social drinker, a few drinks here and there on occasions

That probably didn't affect my development, right? But how do I know? You see, we've got these biological frameworks that we exist in I'm six feet tall Genetically speaking, unless something went terribly wrong I was going to be in this neighborhood But it could have been that if I had had less nutrients growing up or less exercise I might be 5-10 right but I'm not going to be five-feet The developmental window is kind of set but it's a window

On the converse, if I had maybe higher protein more nutritious meals cause I ate better as a child and exercised more, I might be 6-2 But no matter what I ate or what I did I'm not going to be seven feet So I have this window So if I can measure my ability at any given point I don't know how much higher it could have been or how much lower it could have been based on what happened All I know is that it's possible

So, you look at something like smoking, and smoking reduces oxygen and nutrient flow because it constricts blood vessels, right? When you tighten them blood vessels up, right, now you're restricting the flow of oxygen and nutrients across the placental barrier Every time you have a cigarette the temperature in your hand becomes appreciably different, measurably different It becomes cooler because your capillaries are constricting and you probably don't notice it as you're smoking but it's happening and it's measuring it's measurable, and think about that on a much smaller scale On a chronic level, you can cause serious issues including risk for miscarriage, stillbirth, prematurity, and a thing called SIDS, sudden infant death syndrome We don't know why it does what it does All we know is that not every child of a smoker is going to have these problems, right, because there's individual variability but that children of smokers are at higher risk for dying in the crib after being completely healthy or what appears to be completely healthy Has to do possibly with being able to turn over and placement becomes important, of a child before, because they can't actually move their bodies until they develop upper body strength and that takes time and exercise, right, and so what you have is this set a situations where guess what, the period for the greatest damage is in the first two months

The critical period, the most critical period is the first two months of gestation, a time which many women do not even realize what? They're pregnant And then you have other additional issues if somebody is addicted they may really really want to quit for the sake of the child once they learn that that's that they're carrying a child but it doesn't mean that it's easy easier for them now to quit than anybody else So problems with addiction are serious and problems with causing birth defects in this most critical period are set before the person even knows that they might be pregnant You all have a great weekend and I'll see you on Monday!


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