The presence of at least two embryos in the pregnant woman’s uterus is considered a multiple pregnancy, although we primarily refer to a twin pregnancy (in 95% of cases) and less frequently a triplet or quadruplet pregnancy. When does it happen and why? As the new mother’s age increases (over 35), the likelihood of a multiple pregnancy also increases, while at the same time, many women resort to in vitro fertilization. It also happens when the mother is multiparous (has already given birth more than 4 times) or there is a family history, primarily from her mother’s side.

In any case, we must know that a multiple pregnancy is considered a high-risk pregnancy, as it is often associated with prenatal and perinatal complications and mortality. Additionally, in 20% of cases, it results in premature birth and requires monitoring by an MFM specialist with extensive experience.

Medical monitoring

While prenatal diagnosis of twin pregnancy with ultrasound is easy, the maternal-fetal medicine specialist should be extremely careful and precise in diagnosis in order to decide on the safest method and frequency of monitoring the pregnancy. What is it examining?

Obviously, the monozygotic twins are two identical embryos that develop from a single embryo, and dizygotic twins develop from the fertilization of two different embryos. However, twins are also distinguished by the number of placentas and amniotic sacs. Through the nuchal translucency ultrasound scan, the doctor investigates the presence or absence of a shared placenta and a shared or separate amniotic sac. Their number depends on when the embryos split:

  • If their separation occurred in the first 3 days after fertilization, each embryo has its own placenta (dichorionic twins), and “swims” in its separate amniotic sac (diamniotic twins).
  • If the separation occurred after the first 3 days but within the first week, there is only one placenta common to both embryos (monochorionic twins), but they are still in two separate sacs. This is also the most common type of twin pregnancy.
  • Finally, if the embryos separated after the first week, there is a shared placenta and only one amniotic sac (monoamniotic twins) for both. This is the rarest case because as the two embryos swim in the same sac, their umbilical cords can become entangled.

Instructions for the expectant woman

  • A balanced diet is recommended, following the guidelines of the doctor and the collaborating nutritionist, which will include additional folic acid and increased protein
  • Plenty of rest and no strenuous physical exercise. Swimming and walking are recommended
  • Visits every 2-3 weeks, depending on each case, to the specialist doctor who is monitoring you for early diagnosis and treatment of complications.

Potential risks and how to address them

For an experienced maternal-fetal medicine specialist, the proper monitoring of twin and multiple pregnancies is essentially a matter of routine, regular ultrasound check-ups, and good cooperation with the couple, who should be informed so that any decisions can be made together if necessary.

  • In dichorionic twins, after diagnosis, careful and regular monitoring every 4 weeks (from 22 weeks until the date of delivery) is recommended due to an increased risk of premature birth and intrauterine growth restriction.
  • In monochorionic twins, there is a high probability of vascular anastomoses and transfusion from one twin (donor) to the other (recipient), selective growth restriction, and potential for premature birth. After diagnosis, weekly ultrasound monitoring of the fetus begins earlier (from the 16th week of pregnancy) because the risk of twin-twin transfusion syndrome is high (50%), and both fetuses are at risk, as the recipient twin is significantly large for its gestational age, has heart failure, and is in a sac with a lot of amniotic fluid.

At the same time, we are conducting laboratory tests on the mother for potential anemia, gestational diabetes, and gestational hypertension, as there is a risk of miscarriage and premature placental abruption. A cervical check (TVS) for preterm labor and a cardiotocogram are performed.

If specialized treatment is needed (such as cauterization of vascular anastomoses or the placenta) before the 35th-36th week of gestation, we inform the parents, and together we make the best decision to ensure the health of the pregnant woman and the fetuses, as well as the successful outcome of a calm and natural birth.