Frequency of Twin Births in Developed Countries

The increased incidence of multiple deliveries in Spain, in addition to changes in age at maternity and parity, is attributed to assisted reproductive treatments, but the relative contribution of the latter to this rise remains uncertain, due to the scarce information provided by clinics practicing those treatments. Population based data (1984–2004), including information on mother's age, nationality, marital status, date of delivery, and the characteristics of each (parity, single or multiple), and sex of newborns were provided by the Spanish Institute of Statistics. Twinning and triplet deliveries relate to maternal age, parity, and nationality. For younger ages (≤ 19, 20–24, 25–29) rates remained constant over time, but for older women (30–34, 35–39, ≥ 40) rates increased after 1994. From 1984 to 2004 the percentage of twins of opposite sex increased from 24.31 to 36.58 per cent. Since 1997, Spanish and non-Spanish mothers differentiate with respect to multiple maternity at ages over 30. In addition to unmarried Spanish women, immigrants constitute a reliable reference group that determines the convenience of segregating information on multiple deliveries respecting origin. The proportion of twins and triplets of opposite sex, maternal age, and parity patterns observed are concordant with a differential access to reproductive treatments depending on the woman's age. The present norm regulating the maximum number of fertilizations per cycle and the demand for these treatments explain the high incidence of multiple deliveries in Spain. A modified logistic curve predicts a stabilization of multiple deliveries, which will probably continue to be high in Spain.

Section: Discussionsupporting

confidence: 75%

Section: Multiple Births In Spainmentioning

confidence: 99%

Factors Associated with Recent Increase of Multiple Births in Spain

Fuster¹,

Zuluaga

Colantonio

et al. 2008

“…A study reported that in many South and South-East Asian countries, including China, India, Indonesia, and Pakistan, the twinning rates remains below 10/1,000 births; likewise, the incidence in Latin American countries is similarly low (less than 9/1,000 births; Smits & Monden, 2011). The rate is also higher than the 1980s pre-ART multiple birth incidence in England and Wales (9.6/1,000 births) and several other West European countries (less than 10/1,000 births; Pison & D'Addato, 2006).…”

Section: Discussionmentioning

confidence: 94%

Multiple Births in Sub-Saharan Africa: Epidemiology, Postnatal Survival, and Growth Pattern

Gebremedhin

2014

The study endeavored to assess the epidemiology, postnatal survival, and growth pattern of multiple births in Sub-Saharan Africa (SSA). It was based on the data of 25 demographic health surveys conducted in the subcontinent since 2008. The records of 213,889 children born in the preceding 59 months of the surveys were included. The multiple birth rate was computed as the number of multiple confinements per 1,000 births. Factors associated with multiple births were identified using logistic regression and their survival pattern was assessed using the Kaplan-Meier method. The multiple birth rate was 17.1 (95% confidence interval: 17.7-16.6) and showed considerable variation across the 25 countries included in the study. Odds of multiple births were significantly increased with advanced maternal age, parity, and maternal height but not with wealth index, age at first birth, and month of birth. At the end of the fourth year of age, the cumulative survival probability was as low as 0.77 in multiple births as compared to 0.93 in their counterparts. The odds of neonatal, infant and under-five mortality were 5.55, 4.39, and 3.72 times increased in multiple births, respectively. Multiple births tend to be malnourished than singletons and the odds of wasting, stunting, and underweight were 1.31, 1.83, and 1.73 times raised, consecutively. Nevertheless, multiple births regain their weight-for-age (WFA) and height-for-age (HFA) deficits by the end of the fourth year of age. Counseling pregnant mothers with multiple gestation to give birth at a health institution and providing close medical follow-up during and after the neonatal period can improve the survival of multiple births.

“…Normally, the MZ twinning rate is rarely affected by hereditary and environmental factors, and keeps relatively constant, while the DZ twinning rate is affected by heredity, maternal age, parity, diet and assisted reproductive technologies, and is very different for various populations and periods (Vogal & Motulsky, 1997). After undergoing a progressive decline, the twinning rates reversed in the late 1970s and have increased significantly in industrialized countries, and this has raised considerable concern (Pison & D'Addato, 2006). These phenomena were possibly related to demographic features such as maternal childbearing age, birth control, and assisted reproductive technologies (Eriksson & Fellman, 2004;Olsen, 2001;Steinman, 2006;Wilcox et al, 1996).…”

mentioning

confidence: 99%

The Comparison of Twinning Rates Between Urban and Rural Areas in China

Gan

et al. 2007

Based on the birth record data from the National Vital Statistics in the 1990 Census of China, the present study analyzed the differences between urban and rural areas on monozygotic (MZ) and dizygotic (DZ) twin rates by maternal age in 1989. The twins by zygosity were calculated with Weinberg's differential method. Results show that the MZ and DZ twinning rates in China were associated with maternal age and that there were substantial differences between urban and rural areas. The MZ twinning rates in urban and rural areas were 2.36 pairs and 2.11 pairs per 1000 deliveries respectively, significantly lower than that in most studied populations. Furthermore, our analysis indicated that MZ twinning rates remained relatively constant for mothers under the age group of 36 to 38 years, but rose over this age group in both areas, albeit with a different slope. The DZ twinning rates were strikingly affected by maternal age, but the age for peak DZ rates was found within the age group of 33 to 35 years. In all maternal age groups except for 24 to 26 years, the DZ twinning rates in urban areas were higher than in rural areas. It remains unclear as to why the DZ twinning rates reversed to reach higher values within the older maternal age groups in China, but it is almost certain that the high twinning rates had nothing to do with in vitro fertilization.