What do I need to know about twin pregnancy?
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A twin pregnancy is a pregnancy in which two embryos coexist in the intrauterine cavity and they constitute 1% of all pregnancies (with natural conception). In recent years, however, there has been a significant increase in twin pregnancies. Undoubtedly, the fact that many children are born by IVF has contributed to this. While many couples desire a twin pregnancy and perhaps this is a lifelong dream, it should be emphasised that a pregnancy of this type is considered high-risk and the monitoring is different from that of a single pregnancy.
How does a multiple pregnancy occur?
If more than one egg is released during a woman’s menstrual cycle and each egg is fertilised by a different sperm, more than one embryo can develop and implant in the uterus. This type of pregnancy results in dizygotic (non-identical) twins. On the other hand, when a fertilized egg breaks down, it results in the creation of identical embryos. This type of pregnancy results in monozygotic (identical) twins. Dizygotic (non-identical) twins are more common than identical twins.
What types of twin pregnancies are there?
It is very important to know if the embryos share the placenta and/or amniotic sac. This is because it will have an impact on the type of care during pregnancy and birth. We can have the following types of twin pregnancies:
- Dichorionic transmammary twins: each baby has a separate placenta and amniotic sac.
- Monochorionic transmammary twins: babies share one placenta but have separate amniotic sacs.
- Monochorionic monoamniotic twins: babies share one placenta and one amniotic sac
If babies share a placenta, it usually means they are identical. If they do not share a placenta, they may or may not be identical. Monozygotic twins have a higher rate of complications.
What are the main causes of twin pregnancy?
The use of fertility drugs to induce ovulation often causes more than one egg to be released from the ovaries and can lead to twins, triplets etc. Also, IVF can lead to multiple pregnancies if more than one embryo is transferred to the uterus (during the process of embryo transfer). Finally, heredity and age contribute to the occurrence of twin pregnancies. Women over the age of 35 are more likely to release two or more eggs during a menstrual cycle than younger women. Thus, older women are more likely than younger women to have twins.
Why are we worried about twin pregnancy?
While the impression of a pregnancy with twins is exciting and perhaps a dream for many women, it should be stressed that there is a risk of complications and monitoring is more intensive than for singleton (one baby) pregnancies. The most common complications include the following:
A) Premature birth
Over 60 percent of twins are premature (born before 37 weeks).Premature babies are born before their bodies and organs are fully mature. These babies are often small, with a low birth weight (less than 2,500 grams) and may need help breathing, eating and fighting an infection. Very preterm babies, those born before 28 weeks, are particularly vulnerable. Many of their organs may not be ready for life outside the mother’s womb. and will need care in a neonatal intensive care unit.
B) Gestational hypertension
Women with multiple fetuses are twice as likely to develop high blood pressure during pregnancy. This condition often develops earlier and is more severe than pregnancy with one fetus. It can also increase the chance of placental abruption (early placental abruption).
C) Anemia
Anaemia is more than twice as common in twin pregnancies.
D) Genetic abnormalities
Twins have about twice the risk of congenital (present at birth) abnormalities, including defects of the nervous system (such as the spine), gastrointestinal and heart defects.
E) Twin transfusion syndrome
Transfusion twin syndrome (TTTS) is a placental condition that develops only with identical twins who share a placenta. Blood vessels are connected within the placenta and divert blood from one fetus to the other. It occurs in about 15% of twins with a shared placenta. In TTTS, blood is shifted from one fetus to another through blood vessel connections. Over time, a fetus that receives too much blood can overload its cardiovascular system and cause a large amount of amniotic fluid to develop. The smaller fetus (donor) does not receive enough blood and has low amounts of amniotic fluid.
F) Delivery by caesarean section
The abnormal fetal positions often seen in twin pregnancies increase the chances of delivery by caesarean section.
G) Postpartum bleeding
Large placental area and an overly dilated uterus put a mother at risk of postpartum bleeding
In conclusion, twin pregnancy is a pregnancy that should be monitored more systematically than other pregnancies, as there is a risk of complications. In cases (e.g. IVF) where we can avoid this risk, it is advisable (e.g. by transferring a single embryo)
SEE ALSO
Bibliography
- Norwitz et al. Maternal physiology and complications of multiple pregnancy. semin Perinatol. 2005 Oct;29(5):338-48.
- Dodd et al. Evidence-based care of women with a multiple pregnancy. Best Pract Res Clin Obstet Gynaecol. 2005 Feb;19(1):131-53.
- Ozturk et al. Avoiding multiple pregnancies in ART: evaluation and implementation of new strategies Hum Reprod. 2001 Jul;16(7):1319-21.
- Bamberg et al. Update on twin-to-twin transfusion syndrome.Best Pract Res Clin Obstet Gynaecol. 2019 Jul;58:55-65.
