Dizygotic twinning

Abstract

The tendency to conceive spontaneous dizygotic (DZ) twins is a complex trait with important contributions from both environmental factors and genetic disposition. Twins are relatively common and occur on average 13 times per 1000 maternities, though the twinning frequency varies over time and geographic location. This variation is mostly attributed to the differences in DZ twinning rate, since the monozygotic twinning rate is relatively constant. DZ twinning is in part under genetic control, with mothers of DZ twins reporting significantly more female family members with DZ twins than mothers of monozygotic twins. Maternal factors such as genetic history, advanced age and increased parity are known to increase the risk of DZ twins. Recent research confirmed that taller mothers and mothers with a high body mass index (30>) are at greater risk of DZ twinning. Seasonality, smoking, oral contraceptive use and folic acid show less convincing associations with twinning. Genetic analysis is beginning to identify genes contributing to the variation in twinning. Mutations in one of these genes (growth differentiation factor 9) are significantly more frequent in mothers of DZ twins. However, the mutations are rare and only account for a small part of the genetic contribution for twinning.

Mortality among twins and singletons in sub-Saharan Africa between 1995 and 2014: a pooled analysis of data from 90 Demographic and Health Surveys in 30 countries

“…These results are in agreement with findings from studies in more developed countries. 31 Twins were more likely than singletons to have been born in a medical setting (62·5% vs 52·7%) and to have had some medical assistance at birth (51·7% vs 40·4%). These associations might have been to the benefit of twins, but with regard to birth size they were disadvantaged.…”

The Swedish Twin Registry: Establishment of a Biobank and Other Recent Developments

“…It is likely that the latter increase reflects the introduction of IVF. The causes behind the prior decrease are less obvious, but may reflect secular changes in maternal age, parity, smoking, or BMI, factors all known to be associated with DZ twinning (Hoekstra et al, 2008(Hoekstra et al, , 2010. After a gradual adoption of the single embryo transfer (SET) policy in Sweden (rate of SET was 1.5% in 1991, 30.6% in 2002, 54.3% in 2003, and 67.4% in 2004), a marked decrease of IVF-induced multiple births, from 35% in 1991 to less than 5% in 2005 (Karlstrom & Bergh, 2007), has occurred.…”

Study Of Maternal And Fetal Outcome In Twin Gestation At Tertiary Care Teaching Hospital

“…Globally, the highest burden of multiple births has been found in sub-Saharan Africa, with an average twining rate of 20 per 1,000 deliveries compared to 10 per 1,000 deliveries in Europe or around 5-6 per 1,000 deliveries in Asia. Nigeria has the highest prevalence of multiple births worldwide [1][2][3] . Twining is a multi factorial phenomenon principally attributable to genetic and environmental factors, such as advanced maternal age and increased parity.…”

“…Twining is a multi factorial phenomenon principally attributable to genetic and environmental factors, such as advanced maternal age and increased parity. 4,1,2 In India, twinning occurs in approximately 1% of pregnancies and has been reported to be responsible for 10% of perinatal mortality. [4][5][6][7] The incidence of twins is on rise due to variety of reasons like increased use of assisted reproductive techniques and increasing number of women having pregnancy at advanced age.…”