Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Triplets are three babies carried in the same womb during a single pregnancy. Like twins, triplets and other higher-order multiples can be categorized by their zygosity or degree of genetic similarity. Though triplets are most commonly fraternal dizygotic or trizygotic , it is possible for triplets to be identical monozygotic.
While many people are familiar with the terms "identical" and "fraternal" in describing multiples and use them to describe whether twins or triplets look similar, what these terms actually refer to is how the multiples formed in utero. Monozygotic or identical multiples form from the same egg. In the case of identical twins, the fertilized egg splits in two. In the case of identical triplets, the egg may split just once into three or it may split twice where the egg splits first in two and then one of the two splits again , resulting in three embryos with the same general DNA characteristics.
Monozygotic triplets are always the same sex, either all boys or all girls. Some monozygotic triplets are actually quadruplets where one embryo has vanished or been reabsorbed. Research on the prevalence of monozygotic triplets varies. A case report of a healthy set of spontaneously conceived three identical triplet boys lists the incidence at 1 in , live births. Most reported cases are conceived through assisted reproductive techniques.
That paper noted that only seven other cases of spontaneously conceived identical triplets were known. A paper states the rate of incidence of identical triplets is times more frequent with assisted reproductive techniques than spontaneous conception but is still extremely rare. A monozygotic triplet pregnancy carries the risks of a monozygotic pregnancy with a shared placenta, plus the additional risks of a triplet pregnancy.
A pregnancy of this type could be more likely to encounter problems such as preeclampsia , preterm labor , or transfusion syndrome. Most triplets are trizygotic, meaning that each individual formed from a separate zygote , or egg and sperm combination. When identical triplets are formed this means that all three share the same identical DNA , gender, characteristics and features. Some researchers believe that a certain percentage of monozygotic triplets actually start as identical quadruplets but one of the embryos does not continue to grow to maturity or becomes reabsorbed.
See Vanishing Twin Syndrome. But you could suspect you are having a multiple pregnancy because of your exaggerated pregnancy symptoms. Extreme nausea, having an obvious pregnancy belly much earlier than expected or being unable to hold even the smallest volume of wee in your bladder may all raise your suspicions. Triplet pregnancy is confirmed by ultrasound and this can be done in the first trimester of pregnancy, based on pregnancy symptoms. It may not be clear in the very early stages of pregnancy if the triplets are identical or not.
If they share a placenta, this is a strong and definitive sign that they are identical. However, it can be very difficult to determine via ultrasound the exact placental structure. Separate placentas can also fuse making them appear to be one. When a triplet pregnancy is confirmed, it is standard obstetric practice for a woman to require more frequent ante natal checks, ultrasounds, pathology work and general health checks. Bed rest may be ordered if there is a threat of miscarriage or premature labour.
Some women who are pregnant with multiple babies need to spend many months in hospital, especially if they are threatening to miscarry and their pregnancy is at risk. Well this can be tricky. Even parents of identical triplets say they can get confused about which baby is which.
This is why many have developed little tricks to help tell their babies apart and not get them confused with each other. It immediately starts dividing, quickly increasing the number of cells. If more than one egg is available to be fertilised then two or more separate zygotes may start dividing side by side. If it splits completely into two separate groups of cells very early in this division then identical twin zygotes are formed. Cell division continues until each zygote has become a ball of cells which implants attaches and embeds into the lining of the womb and becomes an embryo.
Each embryo will eventually become a baby. As the balls of cells implant into the wall of the womb uterus , they meet up with some specialised cells from the mother's womb and, between them, start to form the afterbirth placenta. The placenta is crucial to the pregnancy - it is the place where your body 'meets' your baby directly to pass across the nutrients your baby needs to grow.
Although your blood and your baby's blood do not actually mix with one another ie you don't share the same circulation , in the placenta your blood and your baby's blood come close together. The ball of cells now starts to form distinct areas, including a central group of cells which will form your baby and the outer cells which will form the amniotic sac membranes.
The membranes have two layers - an inner lining called the amnion and an outer lining called the chorion. In identical monozygotic pregnancies there may be one shared placenta, or the babies may have their own placentas. Where there is one shared placenta, this is called a monochorionic pregnancy. There will be one, shared chorion outer membrane.
When there is one chorion, there may be just one amnion monoamniotic with all the babies in the same sac of fluid, or there can be more than one amnion, as babies can have their own individual sac of fluid inside the one chorion. The different types of multiple pregnancy have different risks and possible problems see below. Pregnancies in which the babies share one placenta have a slightly higher risk of problems. Dizygotic twins each have their own placenta, amnion and chorion.
The same is true for non-identical triplets. Each fetus develops separately in its own sac with its own blood supply. Although the two placentas can be fused together, each connects to only one baby. Multiple pregnancy occurs in nature. In some cases the woman produces more than one egg ovulates. In others there is just one egg fertilised but it splits into two zygotes. Multiple pregnancy is more likely after fertility treatments, particularly assisted reproductive techniques such as in vitro fertilisation IVF.
This is because it is usual for more than one embryo to be transferred to the womb uterus. In the early days of IVF doctors transferred large numbers of embryos into the womb, as many were lost. However, this resulted in a few women becoming pregnant with very large numbers of babies in some cases six or more , making the chance of each baby's survival very small and the risks to the health of the mother very large. There is now a strict restriction on the number of embryos put into the womb after fertility treatment.
Multiple pregnancy is more common in some parts of the world than in others. It is least common in Japan and most common in parts of West and Central Africa. In the UK multiple pregnancy occurs naturally in around 1 out of every 80 births, and identical twins occur only in around 1 in pregnancies.
The overall rate of multiple pregnancy in the UK is about 1 in 60 births - because of the extra multiple pregnancies caused by fertility treatment. The chance of having twins increases if you are older. As you get older, you naturally produce more ovulation-stimulating hormones, which can trigger the ovaries to release several eggs in a single month.
The tendency to have non-identical twins also runs in families passed down the maternal line ; however, having identical twins seems to be entirely down to chance. If you are pregnant with more than one baby, you will have more intensive antenatal care.
This means you will have more check-ups and more ultrasound scans. Multiple pregnancy is usually first recognised at your first ultrasound scan. For most women, this is when you are weeks pregnant. Women who have had IVF and some women who have had bad morning sickness hyperemesis gravidarum will have had an earlier scan and will know sooner. The to week scan is to check the babies' age, how many babies there are and whether or not they share a placenta.
The scan is exactly the same for women with multiple pregnancy as for women with one baby; however, it takes a little longer as there is more than one baby to check. The scan also forms part of the test for Down's syndrome the other part being a blood test. After this, the number and frequency of your scans will depend on your individual circumstances.
Scans allow the antenatal team to check your babies are growing as they should, and allow early detection of some of the problems twin babies can experience. If your babies are not growing well, or if one baby is growing significantly better than the other, you may be referred to a specialist fetal medicine centre for further care.
They will carry out specialist scanning to assess the babies. You will have blood tests at least twice in your pregnancy to check you are not becoming anaemic.
If you have symptoms of anaemia you may have extra tests. The symptoms of anaemia can be vague and include tiredness, breathlessness and fainting. Anaemia is common in pregnancy and even more common in multiple pregnancy.
Generally speaking, medicines should be avoided in pregnancy unless taken on the advice of a health professional. Women who are at risk of high blood pressure in pregnancy may be advised by their specialist to take a low dose of aspirin.
Your specialist will advise if this applies to you. Deciding whether to have the test for Down's syndrome is more complicated for multiple pregnancies. The test is less accurate in determining this risk in multiple pregnancies. Your antenatal team will give you information to help you decide whether to have the test.
If you have a higher risk result you will be offered an invasive diagnostic test. There are other non-invasive DNA tests for Down's syndrome available in the private sector. You will usually be in the hands of a team of specialists, made up of the ultrasonographer, your midwife and a doctor who specialises in pregnancy and childbirth an obstetrician.
You may also be referred to other specialists for advice if you have other problems. The highest-risk multiple pregnancies are cared for by a specialist 'fetal medicine centre'.
This is more likely if you are having three or more babies, or if any of your babies share a placenta. General advice about diet and lifestyle in pregnancy applies to women who are pregnant with more than one baby.
0コメント