But what about twin pregnancies, which involve the arrival of twins? While having a baby is already quite an adventure for the mother-to-be, a twin pregnancy is not without consequences, whether in terms of medical care or the new rhythm of life. In this article, you'll find out everything you need to know about the formation of twins, the medical care required and the risks involved.
What is a twin pregnancy?
A pregnancy is said to be twin when two fetuses develop simultaneously in the uterus, resulting in the birth of twins. But this is not a multiple pregnancyThis would require 3 or more fetuses. Although twin pregnancies have been on the increase for several decades, they are still considered "at risk".
How are twins formed during pregnancy?
Before going into further detail, let's remember that there are two types of twin formation. A distinction is made between fraternal twins (dizygotic) and identical twins (monozygotic). The distinction is made on the basis of the type of fertilization. Only an ultrasound scan can reveal with certainty whether they are fraternal twins (dizygotic) or identical twins (monozygotic).
Dizygotic twins
In this case, two ova are fertilized by one sperm each, and nest next to each other in the uterus. Fraternal twins are the most common type of twins, and are referred to as dizygotic twins.
The term "fraternal twins" refers to the fact that the two babies remain totally independent of each other, each with its own placenta and amniotic fluid sac.
Children born from a disygotic twin pregnancy may be of the same sex (two girls or two boys), or of the opposite sex (one boy and one girl). In terms of physical appearance, they may look alike, but like siblings, with clear differences!
Identical twins (monozygotic)
In the case of "identical twins", or monozygotic twins, a single egg is fertilized by a single spermatozoid, but the egg then divides into two equal and distinct parts. The result? Two embryos develop side by side, with the same genetic make-up. Identical twins always have the same sex (two boys or two girls) and look very much alike. They may develop in the same placenta and amniotic fluid sac, or in two separate sacs and placentas.
How to determine whether a pregnancy is twin?
Do you have signs of early gestation? Perhaps you've even taken a test that proved positive? However, there's nothing to indicate the arrival of twins, apart from perhaps more intense pregnancy symptoms. more intense pregnancy symptoms (nausea, vomiting, fatigue, increased tension in the breasts). To reliably determine whether you're expecting two babies, there are two possible tests: measurement of beta-hCG hormone levels, and a dating ultrasound.
Abnormal increase in beta-hCG hormones
One of the distinguishing markers is the level of beta-hCG hormones, measured by a blood test. In twin pregnancies, beta-hCG levels are significantly higher than in singleton pregnancies (i.e. more than 30 to 200 IU/L). It also increases more rapidly.
Ultrasound dating
If symptoms are more intense than normal, a twin pregnancy may well be on the way! To determine the presence of twins, adating ultrasound (performed before the 1st trimester ultrasound, as early as the second month, between the 6th and 9th week of amenorrhea) allows you to see the presence of two gestational sacs, or a single gestational sac with two embryos, or to hear the beating of two hearts. However, if this examination is carried out too early, even a professional doctor could miss a twin pregnancy!
What are the chances of a pregnant woman having twins?
Far from being an isolated case, twin pregnancies are becoming increasingly common! In fact, the number of twins has been on the rise for several decades, and is now at an all-time high. A study published in the journal Human Reproduction in 2021 reveals that the rate of twin pregnancies has risen over the last thirty years, from around 9.1 twin births per 1000 births in the 1980s, to 12 since the 2010s. Worldwide, almost one baby in forty is affected.
There are many reasons for this increase. Firstly, the acceleration in the number of MAP (Medically Assisted Reproduction) procedures, which encourage the implantation of several embryos. Ovarian stimulation with hormones and in vitro fertilization increase the chances of giving birth to twins.
Another factor is the decline in the average age of women who become pregnant, as the likelihood of twins increases with age.
What are the consequences of a twin pregnancy?
Although medical advances mean that twin pregnancies can now be achieved without difficulty, it should be noted that the medical profession is even more vigilant in this case, as it is still a "high-risk" situation.
The day-to-day life of parents of twins is also quite different from that of a single child, since it involves almost "double" the work! Finally, in view of the particularities of twin pregnancies, women who are pregnant with two babies benefit from longer, earlier maternity leave.
Greater medical supervision
Twin pregnancies are considered a health risk for the mother, due to the increase in premature deliveries, miscarriage, pre-eclampsia, gestational cholestasis, gestational diabetes and vascular complications.
For the fetus, it can also lead to IUGR (intrauterine growth retardation), prematurity or transfusion-transfusion syndrome (one twin delivers more blood than it receives, while the other receives too much).
In the case of a monochorionic twin pregnancy (the twins being in two different pouches, but in the same placenta), the main risk is transfusion-transfusion syndrome (unequal blood exchange between the fetuses), polycythemia anemia or IUGR (intrauterine growth retardation). Women with monochorionic twins benefit from a monthly consultation and increased monitoring through ultrasound scans (once a fortnight). In short, the gynecology department becomes a place to visit again and again!
In the case of bichorionic twin pregnancies, women are invited to have one ultrasound scan per month to check that everything is going well.
Changes in lifestyle
The arrival of two babies is a huge change in a parent's daily routine! Fatigue can be more intense, and organization a little tricky at first, just after giving birth. Don't hesitate to enlist the help of friends and family, whether it's to run errands or help prepare meals in advance!
The trap to avoid? Buying everything twice! Think about "second life" products, and check out the classified ads on the Internet for baby cots and strollers.
Early maternity leave
The length of maternity leave is governed by law, and includes prenatal and postnatal leave, adapted to the family situation, the course of gestation and the conditions of the child's birth. In the case of twin pregnancies, maternity leave lasts 34 weeks, including 12 weeks prenatal leave before the expected date of delivery, and 22 weeks postnatal leave afterwards.
In this situation, the mother-to-be can bring forward her prenatal leave (by up to 4 weeks), reducing her postnatal leave by the same amount, or postpone part of her prenatal leave (by up to 3 weeks) until after the birth.
What are the risks of a twin pregnancy for babies?
There are a number of dangers for babies born of twin pregnancies, which explains the increased medical surveillance required.
First danger: premature birth! As the uterus increases in volume much more rapidly, labor may be induced before term. In fact, around half of all babies in this situation are born before the 36th week! While premature labor can occur on its own, it can also be induced by the medical profession, particularly in cases ofplacental abnormality, abnormal growth of one of the babies orhigh blood pressure in the mother.
Another risk, already mentioned above, is transfusion-transfusion syndrome, which occurs when one of the two babies receives a much greater quantity of blood than the norm, to the detriment of the other fetus.
Finally, when the fetuses share the same amniotic sac, the umbilical cords can become entangled, at the risk of cutting off blood circulation and causing the death of one of the two babies.
Classic, but not dangerous, babies born in twos or more often have a lower birth weight!
Twin pregnancy FAQs
Which parent transmits the gene linked to twin pregnancy?
It can indeed be hereditary! In the case of dizygotic (fraternal) twins, it would appear to be the mother who transmits the gene. In the case of monozygotic (identical) twins, the situation is different: they are the offspring of a single egg fertilized by a single sperm. The formation of monozygotic twins is not directly linked to hereditary factors, but is considered a random event.
What is the normal duration of a twin pregnancy?
The normal duration of a twin pregnancy is often shorter than that of a conventional gestation. On average, it ends spontaneously at around 36 weeks' amenorrhea, and Caesarean sections are more frequent (between 37 and 41 weeks' amenorrhea for a single pregnancy), but without any major health consequences.
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