Demographic parameters and twinning: a study in Catalonia, Spain

Area of Science:

• Reproductive Epidemiology
• Human Genetics
• Demography

Background:

• Twinning rates provide insights into reproductive patterns and potential environmental or genetic influences.
• Understanding variations in twinning rates is crucial for obstetrics and population studies.

Purpose of the Study:

• To analyze twinning rates in Catalonia, Spain, during 1975-1979.
• To investigate factors influencing dizygotic (DZ) and monozygotic (MZ) twinning rates.
• To examine the sex ratio among twin births.

Main Methods:

• Analysis of twinning data from Catalonia (1975-1979).
• Calculation of crude and standardized twinning rates.
• Multiple linear stepwise regression to identify influencing factors (parental age, birth order).
• Sex ratio determination for twin births.

Main Results:

• Low crude twinning rates (7.62 per 1,000 maternities) observed.
• Dizygotic twinning rate (DZTR) was 3.74, and monozygotic twinning rate (MZTR) was 3.88.
• Standardized rates confirmed low overall twinning frequency.
• Sex ratio slightly favored female births (0.49 male vs. 0.51 female).
• MZ rates correlated with birth order and father's age.
• DZ rates correlated with mother's age and birth order.

Conclusions:

• Catalonia exhibited low twinning rates during the study period.
• Parental age and birth order are significant determinants of twinning subtypes.
• The findings contribute to understanding demographic and genetic factors in twinning.