In recent decades, the probability of having twins has increased considerably due to delayed childbearing and the use of assisted reproductive techniques. In addition, many professionals tend to transfer more than one embryo to increase treatment success rates. That way, if one do not implant, another may do it.
A multiple pregnancy consists of the development of two or more fetuses simultaneously; whereas a twin pregnancy refers only to the development of two fetuses. These types of pregnancies carry numerous risks to the mother-to-be and to the fetus due to changes in the body and the limited space inside the uterus.
Therefore, it is really important to inform couples undergoing assisted reproduction treatment about the possible risks of multiple pregnancy before making a decision.
The different sections of this article have been assembled into the following table of contents.
Risks in the mother
Twin pregnancies are complicated due to the large volume occupied by the development of more than one baby in a woman's body. Her body is going to make an effort to adapt to the overload.
The uterus has to bear an excess weight and may become distended, putting more pressure on other organs. Having twins or more babies also means a larger placenta and higher hormone levels.
Here are the most common risks of a twin pregnancy for moms-to-be.
High blood pressure and pre-eclampsia
High blood pressure due to pregnancy, or pre-eclampsiais one of the most common risks in women with multiple pregnancies. Pre-eclampsia usually occurs around 20 weeks of pregnancy and affects 15-20% of women with multiple pregnancies.
This alteration must be treated immediately, since it causes serious alterations and even death both in the mother and in the fetus.
The most common symptoms of pre-eclampsia are:
- Excess protein in the urine known as proteinuria.
- Severe headaches.
- Altered liver function.
- Decreased urine output.
- Blurred vision or temporary vision loss
This type of diabetes develops only during pregnancy and can cause complications during gestation and childbirth. It occurs in the second half of pregnancy and usually disappears after delivery.
The frequency of having gestational diabetes increases with the number of babies being gestated, so a triple pregnancy is more likely to cause gestational diabetes than a twin pregnancy.
The cause of this alteration is that the hormones in the placenta have a hyperglycemic effect, i.e. they increase blood glucose levels and block insulin. Thus, there is not enough insulin to counteract the effect of all glucose in the blood, leading to gestational diabetes.
Blood glucose levels are higher in gestational diabetes than normal, i.e., above 110 mg/dl on an empty stomach and 140 mg/dl after meals. However, they are not high enough to diagnose chronic diabetes.
Moderate or severe anaemia usually occurs in 40% of multiple pregnancies and blood transfusion is required in 5% of cases.
Anemia is a reduction in the number of red cells in the blood. During pregnancy, iron requirements are very high because the needs of the woman and the fetus must be met. In addition, iron is necessary for the formation of the placenta.
For these reasons, in a twin or multiple pregnancy, iron levels must be higher in order to meet the needs of all fetuses and the surrogate.
Hyperemesis gravidarum consists of intense and persistent nausea and vomiting during pregnancy. It is a very common alteration in the case of multiple pregnancies. It may cause dehydration, weight loss, etc.
Its aetiology is unknown, although some risk factors are:
- High levels of Beta-hCG and estrogens.
- Placental weight typical of multiple pregnancies.
- Psychological and family aspects. Refers to moms-to-be who have family members who have experienced nausea and vomiting during pregnancy.
Risks in fetuses
When it comes to twin pregnancies, fetuses may have different risks associated with low birth weight, prematurity, or increased likelihood of genetic alterations. In addition, twin to twin transfusion syndrome can occur in which one fetus receives excess blood and the other receives a deficiency due to the communication of its blood vessels.
Here are the different risks to the fetuses of a twin pregnancy.
Low birth weight
Low birth weight of fetuses is associated with prematurity. As the number of fetuses increases, the birth weight decreases.
Babies born with low birth weight are more likely than babies born with normal weight to have certain health problems, such as retinopathy or changes in breathing, especially during the first year of life.
A baby has a low birth weight when its weight is less than 2,500 kg.
Intrauterine growth restriction
In 30% of twin pregnancies, one of the fetuses suffer from intrauterine growth restriction because they share nutrients from the placenta.
Intrauterine growth restriction (IUGR) refers to those fetuses that are smaller than normal as a result of problems with placental function. As time goes by, the twins will grow and develop smoothly, as the problem of the malfunctioning placenta disappears once out of the womb.
Twin to twin Transfusion Syndrome
In a monochorial pregnancy, in which both fetuses share a placenta, twin to twin transfusion syndrome (TTTS) may occur. In these cases, one of the fetuses receives an excess of blood and the other a deficiency due to the communication of their blood vessels.
A monochorial pregnancy refers to identical twins that share the placenta. In addition, it can be divided into monoamniotic or biamniotic, depending on whether they share the amniotic sac or not respectively.
This is a serious complication of pregnancy that can end in intrauterine fetal death, although it is not the most common.
Here are the 5 stages of TTTS according to severity:
- Stage 1
- there is an increase in amniotic fluid (polyhydramnios) in one fetus, while in the other there is a defect (oligohydramnios).
- Stage 2
- we cannot identify the bladder of the donor fetus.
- Stage 3
- haemodynamic changes occur due to altered fetal circulation in the recipient and/or donor.
- Stage 4
- hydrops occur, i.e. an accumulation of serous liquid in the fetal compartments.
- Stage 5
- it is the most severe stage, as it involves the intrauteine death of one or both twins.
Evanescent twin syndrome
Evanescent twin syndrome, also called vanishing twin syndrome is the loss of one of the fetuses in the first trimester of pregnancy. It usually occurs before the 16th week of pregnancy and is very common in multiple pregnancies.
In these cases, the fetal tissue is reabsorbed by the mother, placenta, or by the other fetus. Vaginal bleeding, such as a common abortion, occurs on numerous occasions. However, the other fetus continues to develop inside the uterus.
The causes of evanescent twin syndrome are not known. However, there are studies that indicate as possible etiology various chromosomal alterations in the embryo since its formation.
Risks during the delivery
Complications that endanger the lives of the mother and the babies can occur at the time of delivery and after delivery. These are usually more common when it comes to multiple pregnancies.
Placenta previa is a problem that occurs in pregnancy due to the presence of several placentas or a single large placenta. Therefore, the position may not be correct and the placenta may be located in the lowest part of the uterus partially or completely covering the cervix. As a result of this alteration, vaginal bleeding and even premature delivery may occur.
Fifty percent of twin pregnancies end before 37 weeks of pregnancy, which means preterm delivery. In addition, the percentage of preterm birth increases to 90% for multiple triplet or quadruple pregnancies.
Babies born prematurely may have health problems, as they must face certain complications such as feeding or breathing difficulty, etc.
This is a high-risk situation for the fetus that can be increased by factors in the mother such as infection, pre-eclampsia, or gestational diabetes.
In more severe cases of prematurity, the baby is at greater risk for respiratory distress syndrome (RDS), intracranial hemorrhage, cerebral paralysis, etc. This applies to babies born before 32 weeks or weighing less than 1,500 grams.
The presence of a large placental area and a very distended uterus put a woman at risk for bleeding after childbirth. Excessive bleeding occurs before or after the placenta is expelled.
Here are the most common causes of postpartum hemorrhage:
- Remains of the placenta that remain attached.
- Inability of the uterus to contract, so it cannot press on blood vessels.
- Vaginal tears
- Coagulation problems
Twin pregnancy in surrogacy
The surrogacy procedure is something so complex and so emotionally and economically demanding that many couples prefer to transfer two embryos to ensure success without worrying about the option of having twins. However, they do not take into account all the problems it can involve.
The possibility of having twins by surrogacy is exactly the same as having twins by in vitro fertilization. Therefore, it will depend on the number of embryos that are transferred, which is conditioned by the agreement between the intended parents, the surrogate and the specialist doctor. Moreover, it is important to know that the number of embryos that can be transferred will depend on the country where the surrogacy takes place.
Intended parents in the surrogacy process are advised to consider the risks of twin pregnancy.
FAQs from users
Is the discomfort greater in a twin pregnancy than in a normal pregnancy?
Yes, when there is a twin pregnancy, that is to say, the development of several babies inside the uterus means a greater effort for the mother's organism. This means that there is an increase in the usual discomfort of pregnancy and also numerous risks, such as pre-eclampsia, diabetes, anemia, overweight, etc.
In a twin pregnancy, does labor always occur by cesarean section?
No. If the size and weight of the babies are appropriate and they are placed in the correct position, a natural birth can be chosen. However, many doctors prefer to perform a direct cesarean section to prevent complications that may arise.
What consequences can evanescent twin syndrome have on the other fetus?
There are numerous studies that indicate the various consequences suffered by the fetus that survives after the evanescent twin syndrome. If the loss occurs before the 8th week of gestation, organs such as the heart of the surviving fetus may be damaged.
However, evanescent twin syndrome does not usually have serious consequences for the twin, which continues to develop if it occurs in later weeks of pregnancy.
Suggested for you
Pregnancy in general is a condition that can involve risks. In the case of a pregnancy in a surrogacy process, there are also risks. If you want to have more information about this , we invite you to click on the following link: Pregnancy Risks During Surrogacy
In addition, we talked about surrogacy. If you want to learn more about it, you can read the article What Is Surrogacy & How Does It Work? – Everything You Should Know.
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FAQs from users: 'Is the discomfort greater in a twin pregnancy than in a normal pregnancy?', 'In a twin pregnancy, does labor always occur by cesarean section?' and 'What consequences can evanescent twin syndrome have on the other fetus?'.