Nuts & Bolts of Twinning

DNA or deoxyribonucleic acid is the chemical of which our genes are made. Every cell in the human body (with the exception of red blood cells) contain the exact same complete compliment of our DNA. The four chemical subunits of DNA are strung together in a chain-like a four-letter alphabet spelling out our genetic instructions. The human instruction manual is made up of approximately three billion letters. Any two random individuals will have millions of differences in their genetic alphabet. Even close family relatives will have many differences in their genetic makeup although they will be much more similar than a random person. The only two people that can share the same genetic makeup with another human being are monozygotic twins.

There are families that have multiple sets of monozygotic twins within a couple of generations, however, monozygotic twinning is not thought to be genetic, rather occurs randomly. As of today, scientists are not sure what causes the egg to split after fertilization. Mothers bear monozygotic twins in no particular age group, rather parallel in age to singleton births. Dizygotic twinning conversely, is thought to be genetic. We have talked with families containing more than 50 sets of dizygotic twin pairs and higher orders of multiples. Mothers bear dizygotic twins later in their fertile lifetime. Usually between 35-39 years of age. On average, mothers of dizygotic twins are taller and heavier than mothers of monozygotic twins. There are many theories for the birth of multiples ranging from “old wives tails” about the method of conception to contradicting scientific studies. A recent theory that has been traveling through scientific circles indicates that as many as 60% of all births at the molecular level start as twins, with one twin never making it past the early stages of life.