Why Is A Twin Brother Always Smaller Than The Other?


When twins are born, one expects to find two exact copies. That the expression “like two drops of water” is literal, but there are always differences and the main one is that one baby is smaller than the other. Doctors have attributed this to genetic or risk factors such as poor mother feeding or smoking, but scientists at Boston Children’s Hospital believe it is due to a slow transfer of oxygen between the mother and the fetus during pregnancy.

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And is that although the twins share the same placenta, it is divided into two different compartments and it is likely that one is much healthier than the other. A study led by the director of the hospital, P. Ellen Grant and Dr. Elfar Asalsteinsson, has shown that there are dysfunctional placentas with areas that do not reach the oxygen and nutrients necessary for proper growth of the babies.

Now, with the help of a novel technique based on ultrasound and developed in the center, the team has been able to observe in real time how oxygen reaches the twins and how it affects their development before birth. They monitored 7 mothers who were between week 29 and 34 of their pregnancy and gave them pure oxygen for 10 minutes to study the time it took to reach their maximum concentration in the placenta (TTP – Time to Plateau ) And what it took to pass through the umbilical cord to the brain of the fetus and its liver. After the study, they found that when oxygen took longer to reach the baby, their growth was reduced.

Grant hopes that her team’s work will be used to better understand pregnancy risk factors, to develop a prenatal test for mothers in whom placental dysfunction may be suspected and thus improve prenatal care.




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