We talk about twins or multiples when instead of one expected baby, two, three or more children are born at once. However, multiple pregnancies are not without risk.
What are twins and multiples?
According to the Hellin rule, one in 85 pregnancies is a twin pregnancy. Multiple pregnancies with at least two children are considered rare. According to the Hellin rule, one in 85 pregnancies is a twin pregnancy. One in 7,000 mothers has triplets on average, while a quadruplet pregnancy occurs on average only once in 600,000 pregnancies. In recent decades, however, there has been an increase in multiple pregnancies. This is due to artificial insemination and special treatments with hormones to stimulate fertility. In modern times, approximately every 50th mother carries multiples. In the context of artificial insemination, the probability of multiples is even relatively high. Thus, during in vitro fertilization, several ovulations occur at the same time. After fertilization, which takes place in a test tube, three or four embryos are then transferred to the female uterus. In this way, the probability of pregnancy is supposed to be increased. However, it can happen that not only one baby grows up, but two, three or four children. About one fifth of all women who undergo artificial insemination become pregnant. In every fourth pregnant woman, a multiple pregnancy occurs.
Function and task
Multiples, such as twins, triplets, or quadruplets, do not have a special biological function. However, they do increase the reproductive rate. Sometimes, however, multiple pregnancies are considered a burden because they take up a lot of the parents’ daily lives. Nevertheless, multiples are definitely considered an enrichment. The children can grow up together and in most cases develop a special relationship with each other. If the children’s lives are well organized, the everyday life of multiples will also proceed in an orderly fashion. With multiples, it is important to distinguish between identical and fraternal children. About 30 percent of all twins are identical. Thus, they have the same sex as well as the same blood group. Another characteristic of monozygotic twins is their external similarity. Identical twins are formed when an egg cell is divided into two nuclei after fertilization. Both nuclei have identical genetic material. If the division takes place within three days, two germinal vesicles are implanted in the uterine mucosa. The two embryos can develop there side by side. Each embryo has its own chorion and amniotic cavity. In addition, there is a connection to the mother via her own placenta. If the egg divides after four days, two amniotic cavities and only one chorion are formed. Both children receive their supply from the same placenta of their mother. If the division occurs after eight days, both embryos are developed in the same chorion and amniotic cavity. Also in this case, the supply is provided by the same placenta. A division after 12 to 14 days is questionable, because it leads to the development of conjoined twins. In this maldevelopment, both children are physically fused to each other. In contrast to identical twins, fraternal twins usually differ from each other in the same way as ordinary siblings. Triplets, quadruplets or further multiples usually result from artificial insemination. However, the babies are always fraternal. It is not uncommon that they consist of different combinations of monozygotic and dizygotic children. A multiple pregnancy is detected by sonography (ultrasound examination), which takes place between the 9th and 12th week of pregnancy. Because the embryos are still very small at this time, they can be imaged at the same time.
Diseases and medical conditions
Because multiple pregnancies place a health burden on the expectant mother, doctors classify them as high-risk pregnancies. Thus, women expecting multiples must take good care of themselves. Because multiples also add body weight, they can put strain on the spine and legs. Muscles and connective tissue are also subject to greater stress.It is not uncommon for multiple mothers to suffer from complaints such as back pain, high blood pressure, sleep problems, blood congestion in the legs, varicose veins, anemia (anemia), constipation and diaphragmatic hypertension. The latter often leads to breathing problems and heart problems. Especially in the last trimester, the pregnant woman must avoid unnecessary stress and physical exertion at all costs to rule out premature onset of labor. A multiple pregnancy also means an increased risk for the unborn children. For example, there is a risk of premature birth if cervical insufficiency or premature rupture of the membranes sets in. As the number of growing children increases, the duration of pregnancy also shortens. For example, a normal pregnancy takes 267 days, while a twin pregnancy takes only 262 days. In the case of triplets, the duration of pregnancy is 247 days on average. The reason for this is the higher overstretching and strain on the cervix and uterus. In addition, there is weaker blood flow to these two body structures. Conceivable complications of a multiple pregnancy include miscarriages, malformations of the children, growth delays, and fetal transfusion syndrome (FFTS). This is a rarely occurring nutritional and circulatory disorder in which one child develops at the expense of the others. The risk of FFTS is particularly high in the presence of a shared chorion. Furthermore, there is a risk of intrauterine amniotic death. Healthy development of multiples requires uterine care. If each child has its own amniotic cavity and placenta, this is most favorable in twins. However, if both children must share a placenta and amniotic cavity, the risk of complications increases.
