2-3% of live births in the United States, yet they account for 10-15% of the nation’s adverse neonatal outcomes.
Approximately 3-4 of 1000 live births produce genetically identical twins.
Twins are classified as monozygotic or dizygotic.
Monozygotic twinning results in genetically identical individuals arising from a single spermatozoon and oocyte, whereas dizygotic twins share approximately 50% of their DNA sequence identity, as two full siblings with two individuals spermatozoa fertilizing two separate oocytes.
Monozygotic twins are derived from a single fertilized ovum which splits.
Monozygotic twins separate by the 12th day after fertilization.
2/3 of monozygotic twins pregnancies have a monochorionic placenta through which increase perinatal risks or mediated.
Fraternal twins are derived from two independently fertilized eggs and have the same genetic disparity as non-twin siblings.
Rate of twinning increased in women who take dietary folate after in vitro fertilization.
Preterm delivery, low birth weight, and very low birth weight occur much more frequently amount twins than among singletons and contribute to higher rates of mortality, morbidity, and long-term disability.
Abnormal discordance in size between twins at birth defined from 15-40%.
Extreme birth weight discordancy associated with adverse perinatal outcomes and a higher risk of preterm birth, fetal and neonatal deaths.
Birth weight discordance of >15% among same sex and >30% among different twins confer the greatest risk of stillborn and neonatal deaths.
Placental abruption increases the risk of stillbirths and neonatal deaths with discordant weights.
Associating with family risk for specific types of cancer including prostate, melanoma, breast, ovary and uterus.
Twins Study
Exercise can alter genetic markers of metabolic disease, of any of the diseases or disorders that disrupt normal metabolism.
There is a molecular mechanism for the link between physical activity and metabolic disease.
A majority of identical twins develop different diseases as they get older, even though they have the same genes.
Epigenetics indicates that behaviors and the environment affect the day-to-day function of genes.
The twins’ activity, measured by their waistlines and assessed their body mass indexes, and answered questions about their lifestyle and neighborhoods.
In many of the twin pairs, the individuals differed in levels of exercise, neighborhood walkability and BMI.
The more physically active siblings had lower signs of metabolic disease, measured by waist size and BMI.
This correlates with differences in their epigenomes, the molecular processes that influence gene expression.
More active twins had epigenetic markers that were linked to lowered metabolic syndrome, a condition that can lead to heart disease, stroke and type 2 diabetes.
The twin with a high level of physical activity, defined as more than 150 minutes of exercise a week, had epigenetic changes that correlated with reduced BMI and waist size.
The genetic regions where these changes are found are associated with more than 50 genes specific to vigorous physical activity and metabolic risk factors.
Epigenetics may explain why most identical twins develop different diseases as they age.
Ifgenetics and DNA sequence were the only driver for biology, then essentially twins should have the same diseases.
So there is an environmental impact on the twins that is driving the development of disease.