Basic Facts: Science of Multiple Births

A multiple birth occurs where more than one fetus exits the womb in a single pregnancy. Different names for multiple birth are used, depending on the actual multiple. Common multiples are two and three, known as twins and triplets respectively. Twins, triplets and other multiple births occur to varying degrees in most animal species, although the term is most applicable to placental species. There are two common types of multiple births, fraternal (dizygotic) and identical (monozygotic). Identical siblings arise where one egg is fertilised and the resulting zygote splits into more than one embryo. Identical siblings therefore have the same genetic material. Fraternal siblings result from the fertilisation and implantation of more than one egg, so fraternal siblings are not genetically identical, and instead have an analogous genetic similarity of any brothers and sisters. A very rare third type of twinning is now believed to occur when an unfertilized ovum splits into two equal parts prior to fertilization, creating a second complete ovum, called the "polar body". After splitting, both ovum are each then fertilized by different sperm. This results in twins who share half their genes in common (from the mother) and the other half different (from the two sperm). Polar body twins share about 75% of their genetic markers, less than identical twins but more than fraternal twins. They share some features of identical twins and some features of fraternal twins and are so-called half-identical twins. However, DNA-based zygosity tests are currently not available to determine if twins are polar-body twins. The most common form of human multiple birth is twins (two babies), but the typical order of multiple births in other placental species differs dramatically. Some species give birth to multiple offspring as a matter of course and the resulting group of offspring is called a litter. Labels: basics, science

Basic Facts: Multiple Birth Rates

Multiple birth pregnancies have been rapidly increasing due to advancements in infertility treatments. Twin births over the past decade have risen by 33 percent, while higher order multiples have increased 178 percent. More than half of all multiple births are low birthweight. Over 50% of twins and upwards of 90% of triplets are born premature in the U.S. In contrast, approximately 11% of all singleton births are premature. Twin births are 7 times more likely to result in death during the first month of life, and on average, require longer hospital stays resulting from preterm delivery complications. Proper childbirth education and prenatal care during your high risk pregnancy will assist you in achieving your goal of delivery of healthy, term multiples. (Multiple Birth Resources, LLC) Labels: basics, science

Types of Multiple Births: Terminology

Monozygotic - multiple (typically two) foetuses produced by the splitting of a single zygote Dizygotic - multiple (typically two) foetuses produced by two zygotes Polyzygotic - multiple foetuses produced by two or more zygotes Litter - the offspring produced by a multiple birth in non-human placentals Terms used for the order of multiple births are largely derived from the Latin names for numbers. Two offspring - twins Three offspring - triplets Four offspring - quadruplets Five offspring - quintuplets Six offspring - sextuplets Seven offspring - septuplets Eight offspring - octuplets Nine offspring - nonuplets Ten offspring - decaplets Eleven offspring - undecaplets Twelve offspring - duodecaplets Thirteen offspring - tredecaplets Fourteen offspring - quattuordecaplets Fifteen offspring - quindecaplets Labels: basics, science

Definitions of Multiple Births

The most common form of human multiple birth is twins (two babies), but cases of higher orders up to octuplets (eight babies) have all been recorded with all siblings being born alive. The largest set in which all members survived more than a few days is septuplets, the first of which was in 1997. The largest set to have even a single member survive is octuplets, in 1998 (with the seven surviving octuplets born in Texas). There have been a few sets of nonuplets (nine) in which a few babies were born alive, though none lived longer than a few days. There have been cases of human pregnancy which started out with ten, eleven, twelve and fifteen fetuses, but no known instances of live births of such high multiples in a single pregnancy. Most of these pregnancies are a result of fertility medications, though a set of duodecaplets (twelve) was conceived spontaneously (without the aid of fertility treatments) in Argentina in 1992. Multiple pregnancies in humans are usually delivered before the full term of 40 weeks gestation. The average length of pregnancy is around 36 weeks for twins, 34 weeks for triplets and 32 weeks for quadruplets. Labels: basics, science