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Twinning rate in a southeastern Brazilian population
B Beiguelman1, C Franchi-Pinto, H Krieger
1Department of Medical Genetics, School of Medicine, UNICAMP, Campinas, SP, Brazil.
Acta Geneticae Medicae Et Gemellologiae
|January 1, 1996
Summary
Twinning rates in Campinas, Brazil, show a decrease in dizygotic (DZ) twins but an increase in monozygotic (MZ) twins since the 1960s. Overall twinning incidence has stabilized recently.
Area of Science:
- Epidemiology
- Human Reproduction
- Genetics
Background:
- Twinning incidence has varied globally over time.
- Understanding demographic trends in twinning is crucial for reproductive health studies.
- Previous studies in Campinas provide a historical context for current twinning rates.
Purpose of the Study:
- To investigate twinning incidence in Campinas, Brazil, from 1984 to 1993.
- To analyze trends in dizygotic (DZ) and monozygotic (MZ) twinning.
- To update the understanding of overall twinning and triplet rates in the region.
Main Methods:
- Retrospective analysis of twinning data from Campinas, Brazil (1984-1993).
- Combination of new data with previous series from the same population.
- Calculation of mean annual incidences and standard deviations for DZ, MZ, and all twins.
Main Results:
- Mean annual incidences (per 1,000 births) for 1984-1993: DZ twins 4.7 ± 0.92, MZ twins 4.1 ± 1.11, and total twins 8.8 ± 0.87.
- Mean annual incidence of triplets was 0.15 ± 0.16 per 1,000 births.
- DZ twin incidence has decreased since 1925; MZ twin incidence has increased since the 1960s, possibly linked to oral contraceptive use.
Conclusions:
- The declining trend in DZ twinning continues, while MZ twinning shows a recent increase.
- The overall twinning rate's decline has ceased in recent years.
- These trends may reflect changes in reproductive practices, including oral contraceptive use.