What makes some babies come early, and some come late? What tells the female body that it’s time to start labour?
In: Biology
Labor is induced by uterine stretching. Once the baby reaches a certain size, it begins to stretch the walls of the uterus (or the womb). This also triggers the release a hormone know as oxytocin. While oxytocin has many different effects in the body, one of them is to increase uterine muscle contraction, further inducing labor. This cycle is know as a positive feedback loop, and is one of the only positive feedback loops in the human body.
This answers only part of your question, which is what tells the body to initiate labor. However, as another poster mentioned, we don’t know exactly why some babies are born early or late. We do know, however, some risk factors:
– uncontrolled diabetes
-smoking/drinking/drug use
-poor nutrition
-infections like UTIs or amniotic membrane infections
-many more
Nobody really knows for sure. There are risk factors but no way to predict 100% that is why OB is so risky
Delivery of the baby should happen when the fetus is matured enough but before the placenta has reach its end-of-life. The breakdown of the placenta triggers the labour process, according to this article https://www.sciencedaily.com/releases/2015/10/151026132136.htm
Now why does it make sense, evolutionary wise?
The mothers (human, animals) which did not have the right aging of the placenta did not induce labour and died during childbirth (too long lived placenta) or delivered non-matured fetuses (too short lived placenta). As such the genetic blueprint for the right-aging placenta survived.
Now the question of why some are coming too early and too late? Because 40 weeks is not the only time they can survive or be delivered, 39 weeks is fine, 38 weeks is fine, 41 weeks is fine.
This is just a theory I’ve seen in some research papers, but there seems to be suspicion that it’s up to the placenta.
The placenta is an organ that the mother’s body creates and it’s basically what’s in charge of nutrients for the fetus. The umbilical cord connects the baby to the placenta. If the placenta doesn’t have enough blood flow, or if the baby gets too big and demands more nutrients, it can’t do it’s job (this is a problem seen with twins that share a placenta. Often times these pregnancies are risky because one placenta has trouble supplying for two babies).
Anyways, some speculate that the placenta alerts the mothers body when it can no longer supply adequate nutrition to the baby. This explains why younger girls are at higher risk for preterm birth (their bodies have a harder time supplying nutrients), or why high blood pressure causes preterm birth (restricts blood flow to the placenta). The placenta reaches its “capacity” early and causes the baby to come early.
Again, just a theory, but that’s the one that made the most sense to me.
As the others said its not 2+2=4 situation that can be confirmed but many reasons impact it 1.maternal reasons such as diet diseases daily life times that the mother gave birth genetics 2.fetal reasons such as blood circulation fetal diseases sulfactan syntesis fetal position as head first or feet first as well as where in the womb tje fetus is placed low or high etc 3. External stimuli like fear or stress factors trauma familial relationships. So no one answer is wrong and true
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