Twins and triplets: What to expect with a multiple pregnancy

Learning that you’re expecting twins or triplets can bring up a lot of questions. Here’s what you need to know to prepare yourself for the adventure ahead.

Types of multiple births

Twins

There are two types of twins.

• Identical twins
  One egg is fertilized by one sperm, forming an embryo. The embryo then divides into two new embryos, which develop side by side. Both babies therefore have the same genes and are completely identical. They usually share the same placenta, but they may either share an amniotic sac or each have their own. Identical twins occur in roughly 1 out of every 250 births.
• Fraternal twins
  Here, two different eggs are fertilized by two different sperm. The resulting pair of embryos each have their own unique genetic makeup. Fraternal twins have no more similarities than siblings usually do. They occur in roughly 1 to 1.25 out of every 100 births.

Triplets

Triplets can occur in three different ways.

• 3 identical babies
  One egg is fertilized by a single sperm, and only one embryo is formed. This embryo then divides into three new embryos that develop side by side.
• 3 different babies
  Three eggs are fertilized by three different sperm. The three developing embryos each have their own unique genetic makeup. The resulting triplets have no more similarities than siblings usually do.
• 2 identical babies and 1 different baby
  Two eggs are fertilized by two different sperm. Then, one of the embryos divides into two new embryos. The two babies resulting from the divided embryo will be identical, while the third will have a unique genetic makeup.

Risks

Multiple pregnancies are considered high-risk pregnancies because all the risks associated with a normal pregnancy are higher.

Risks to the mother

• Women with a multiple pregnancy are at greater risk of anemia because the extra blood volume is greater than in a normal pregnancy.
• The heart rate increases to pump this extra blood. In addition, women expecting twins are more likely to experience hypertension or preeclampsia during their pregnancy.
• Mothers who are pregnant with twins are also more likely to suffer from gestational diabetes.
• The mother’s lungs and abdominal organs are more compressed, since the babies take up a lot of space.

Risks to the babies

• The volume of the uterus increases more rapidly, which can trigger preterm labour. If this occurs, your prenatal care providers can intervene to prevent labour from progressing. Approximately 60 percent of babies from multiple pregnancies are born prematurely. It is estimated that half of twins are born before 36 weeks, and half of triplets before 32 weeks.
• Preterm labour can commence on its own, but it can also be induced by the medical team for various reasons: one of the babies may not be growing as they should, the mother may have hypertension, or there could be a problem with the placenta.
• Twins and triplets are more likely to have congenital anomalies. According to the Society of Obstetricians and Gynaecologists of Canada, the risk is 1.2 to 2 times higher.
• Some identical twins may also develop twin-to-twin transfusion syndrome. This occurs when one baby receives a large amount of blood at the expense of the other. If the problem is not treated, it can result in the death of both fetuses.
• Twins are more likely to experience fetal growth restriction.
• When fetuses share the same amniotic sac, there is a risk of their cords becoming entangled. This may interrupt blood flow and accidentally cause the death of one of the fetuses.

Pregnancy monitoring

When doing a physical exam, a doctor may be able to determine whether a pregnant woman is expecting twins, as women carrying twins usually have a larger uterus. In addition, when the doctor listens to the baby’s heart with a fetal Doppler, they might be able to hear two different heartbeats. However, twins are usually confirmed at the ultrasound stage.

Given that multiple pregnancies are considered to be high-risk, they need to be monitored a little more closely. Women pregnant with twins or triplets who are being followed by a family doctor or midwife will usually also be jointly followed by a specialized obstetrician.

In the latter part of the pregnancy, medical checkups and exams will become more frequent. For example, more ultrasounds will be done to ensure that the babies are developing well. The purpose of this closer monitoring is to prevent a preterm birth and to detect any complications that could compromise the health of the mother and the babies as soon as possible.

Delivery

When choosing a birthing hospital, parents expecting multiple babies should consider a number of factors, including the stage of pregnancy, known complications, and the availability of qualified personnel. There is a greater chance that labour will be preterm or that it will have to be induced for medical reasons.

Eighty percent of the time, the first baby will present headfirst. In this case, vaginal delivery is recommended. If the first baby is in a breech position, a caesarean section is the most common option, but a vaginal birth is also possible under certain conditions.

In a vaginal birth, the first twin will dilate the cervix and the vaginal canal. This makes it easier for the second baby to come out. However, the second delivery must be carefully monitored, as there can be complications with the umbilical cord or placenta.

If the baby is not positioned properly, the doctor may try to turn them in the uterus. In some cases, especially if the second baby is breech or appears to be in distress, a C-section may be necessary. It is estimated that in 40 percent of twin pregnancies, both babies present headfirst.

In the case of triplets, a C-section is recommended.

Coming home

Coming home with twins is no small task. Don’t be afraid to accept all the help you can get, whether it’s from family, friends, or a postnatal services organization. However, take the time to explain your needs.

You can also plan certain things before the birth. For example, consider cooking large batches of food and freezing them in portions. After the babies arrive, you’ll have ready-made meals that just need to be heated up.

When preparing the babies’ room and accessories, don’t buy everything twice. Instead, borrow certain items from family or friends.

To learn more about going home after a multiple pregnancy, see our fact sheet on having twins (French only).

Things to keep in mind

• Multiple pregnancies are considered high-risk pregnancies.
• Multiple pregnancies require slightly closer monitoring.
• Coming home with twins takes a lot of preparation.

Scientific review: Roxanne Piché, nurse clinician, CHU Sainte-Justine Research and copywriting: The Naître et grandir Team Updated: June 2022