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The epidemiology of multiple births
R Bortolus1, F Parazzini, L Chatenoud
1Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Human Reproduction Update
|May 21, 1999
Summary
Spontaneous multiple births are influenced by genetics for identical twins and environmental factors for fraternal twins. Maternal age and heredity are key determinants.
Area of Science:
- Reproductive biology
- Human genetics
- Epidemiology
Background:
- Spontaneous multiple births, excluding those from fertility treatments, present complex etiological factors.
- Understanding the determinants of multiple gestations is crucial for reproductive health and obstetrics.
Purpose of the Study:
- To review and synthesize the current English literature on risk factors for spontaneous multiple births.
- To differentiate between factors influencing monozygotic and dizygotic twinning.
Main Methods:
- Comprehensive literature search of MEDLINE and manual searches.
- Analysis of English-language publications on spontaneous multiple birth risk factors.
Main Results:
- Monozygotic (identical) twin pregnancy rates remain constant, suggesting a stable genetic influence.
- Dizygotic (fraternal) twin pregnancy rates show temporal and geographical variations, indicating environmental influences.
- Maternal age and family history (hereditary components) are identified as primary determinants for spontaneous multiple births.
Conclusions:
- The etiology of monozygotic and dizygotic twinning likely involves distinct mechanisms.
- Genetic factors appear predominant in monozygotic twinning, while environmental factors are significant for dizygotic twinning.
- Maternal age and heritability are the most established risk factors for spontaneous multiple births.