2017-10-29 12:06:22
In the last decade, a series of studies has revealed striking differences between older and younger brothers and sisters, differences that are not only due to different treatment by their parents or relatives, but are caused, above all, by factors physiological already during pregnancy, well before birth. Early studies made it clear that, in general, in adulthood, older siblings tend to be taller and larger than younger ones. This is in contrast to the recently proven fact that firstborns are smaller at birth than their next siblings. At birth, there is a difference of a few hundred grams in favor of the younger siblings, but this disadvantage is soon overcome and from the age of four, the firstborn reach and begin to exceed their younger siblings in weight. They are also taller than them and by the age of thirteen and a half are about 2.6 cm taller than younger siblings of the same sex.
It turns out that, during the first pregnancy, the uterus and the mother’s body are not as prepared as in subsequent pregnancies. The first placentation does not allow the exchange of nutrients between mother and fetus to occur as efficiently as would be desirable. This supposes that the embryo and the fetus develop in the uterus in a state of relative nutritional deprivation, a deprivation that leads to the baby being born smaller than it should be.
Nutritional deprivation during pregnancy leaves a metabolic imprint on your body that lasts a lifetime. Let’s say that your metabolism is born adapted to an environment with few nutrients, which is not always true, on the contrary. This leads to the fact that, in a situation of nutritional normality, such as that which usually occurs after birth, the metabolism of the first-born tends to store more nutrients in the form of fat. This translates over the years into an increased risk of developing obesity, hypertension and cardiovascular diseases, diabetes, allergies, asthma or autoimmune diseases. In the umbilical cord, T lymphocytes, the main regulators of all the functioning of the immune system, have a more aggressive gene functioning profile in the case of the first-born. It is therefore possible that their immune system is also programmed to react more expeditiously to external threats, but this also increases the risk of developing diseases that involve the proper functioning of the immune system.
All these studies seem to show that older siblings not only suffer more strongly from the possible educational rigors of their parents, but that they are born badly programmed to face the vicissitudes of life from the point of view of their metabolism and their defenses.
More information on Jorge Laborda’s Blog: Big brother syndrome
Referencias: Kragh M et al. Divergent response profile in activated cord blood T cells from first-born child implies birth-order-associated in utero immune programming. Allergy. 2016 Mar;71(3):323-32. doi: 10.1111/all.12799.
Albert BB et al. Among overweight middle-aged men, first-borns have lower insulin sensitivity than second-borns. Sci Rep. 2014 Feb 6;4:3906. doi: 10.1038/srep03906.
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