Expecting Twins in Ajax: How Ultrasound Follows Multiples

Learning that there are two babies, or occasionally more, changes the shape of a pregnancy almost overnight. Alongside the joy and the practical worries about car seats and sleep, many parents notice that their care plan changes too. There are more appointments, more ultrasounds, and new words such as “chorionicity” that nobody mentioned during a single pregnancy.

This article explains, in general and plain terms, why ultrasound plays such a central role in a twin pregnancy and what the scans are trying to answer. It is written for families in Ajax, Pickering, Whitby and the surrounding area. The specifics of your own care will come from your doctor, midwife or obstetric team, who may involve specialists depending on the type of twin pregnancy you have. Use this as background reading so that their plan makes more sense.

The first big question: do the babies share a placenta?

For a twin pregnancy, one of the most important things an early ultrasound can show is how the babies are arranged inside the uterus. Two features are looked at:

• Chorionicity, which describes whether each baby has its own placenta or whether they share one
• Amnionicity, which describes whether each baby has its own amniotic sac or whether they share one

Put together, these give the broad types of twin pregnancy:

Dichorionic twins are generally considered the more straightforward arrangement. Twins who share a placenta are followed more closely, because a shared placenta means a shared blood supply, and that can occasionally lead to imbalances between the babies that providers want to catch early.

Why it is best seen early

The type of twin pregnancy is often easiest to determine in the first trimester. At that stage, the sonographer can look carefully at the membrane between the babies and the way it meets the placenta, which has a characteristic appearance depending on the type. Later in pregnancy, the placentas can grow close together and the membrane becomes thinner, making the distinction harder. This is one reason providers often like an early scan when twins are suspected or confirmed.

Identical or fraternal?

Parents often assume the placenta tells you whether twins are identical. It is a little more complicated. Twins who share a placenta are identical. Twins with separate placentas are often fraternal, but some identical twins also have separate placentas, depending on when the fertilized egg divided. So a dichorionic scan does not settle the question on its own. If it matters to your family, your provider can explain what can and cannot be known before birth.

Telling the babies apart

From early on, the babies are usually given labels, commonly “Twin A” and “Twin B”, based on their position in the uterus. Twin A is often the baby lying lowest, closest to the cervix. The labels help everyone track each baby’s measurements consistently from scan to scan.

Because babies move, sonographers use landmarks such as the location of each placenta, the side of the uterus each baby occupies, or where each cord inserts, to make sure that measurements recorded on one visit are matched to the right baby on the next. It is worth knowing that these labels describe position, and they may not match the order in which the babies are eventually born.

Why twins are scanned more often

A single pregnancy may have only a few ultrasounds in total. A twin pregnancy usually has more. The extra scans are not a sign that something is wrong. They reflect the fact that two babies are sharing space and resources, and that some issues are easier to manage when spotted early.

In general terms, follow-up ultrasounds in a twin pregnancy may look at:

1. Each baby’s growth. Measurements are compared over time for each twin and between the twins. A noticeable difference in size between them is something providers watch for.
2. Amniotic fluid around each baby. In a shared-placenta pregnancy, a difference in fluid between the two sacs can be an early clue that the blood flow between the babies is becoming unbalanced.
3. Blood flow. Doppler ultrasound, which measures the movement of blood, may be used to look at the umbilical cords and other vessels when your provider wants more information.
4. The cervix. Because preterm birth is more common with multiples, some care plans include cervical length measurements.
5. Position. As the due date approaches, the position of each baby helps the care team plan for delivery.

How often scans happen depends strongly on the type of twin pregnancy. Twins who share a placenta are typically scanned more frequently, often from the early second trimester onward, while dichorionic twins may have a somewhat lighter schedule. Your provider will tell you what is recommended for you.

Where the scans happen

Care for a twin pregnancy is often shared. Some ultrasounds may be done at a community imaging clinic, while others, especially for monochorionic twins or when specialized assessment is needed, may be arranged at a hospital or a specialized fetal assessment unit. Your provider will direct you to the right place for each scan.

If your requisition is for an obstetrical ultrasound at our Ajax clinic, call us when you book to mention that it is a twin pregnancy. That helps us allow suitable time and confirm the arrangements for your visit.

What the appointments feel like

Scanning two babies is a bit like doing two exams at once. Everything that is checked for one baby is checked for the other, and the sonographer has to keep track of which is which. A few practical points:

• Expect longer appointments. Allow extra time and avoid booking anything tightly afterward.
• Comfort gets harder sooner. A twin pregnancy tends to grow larger earlier, and lying on your back can become uncomfortable or make you feel light-headed. Tell the sonographer straight away; tilting to one side or a short break usually helps.
• Bring water and a snack for after the scan, unless your instructions say otherwise.
• Keep a scan log. With frequent appointments, a simple note listing each scan date, what it was for, and any follow-up your provider mentioned can save a lot of confusion.

The detailed mid-pregnancy anatomy review is also done for each twin. Our article on the mid-pregnancy anatomy scan explains what that survey covers, and with twins you can expect it to take longer and, quite often, to need a second visit to complete the views for both babies.

Later in pregnancy

As the pregnancy progresses, growth assessments become a regular feature of twin care. Many of the principles are the same as for a single baby, described in our post on third-trimester growth scans, with the added step of comparing the two babies to each other.

Twin pregnancies are also more likely to deliver before the due date, so your provider may talk with you earlier than usual about birth planning, signs of labour, and where you will deliver.

For many families in Ajax and the rest of Durham Region, the final weeks also bring a lot of travel between appointments. It can help to ask your provider early which scans will be at the hospital and which can be done closer to home, so you can plan transport, time off work and childcare for any older children. A support person who can drive is especially useful late in a twin pregnancy, when getting in and out of the car becomes harder.

Signs that need prompt attention

With a twin pregnancy, it is especially important not to wait for a scheduled scan if something feels wrong. Contact your health-care provider or labour and delivery unit right away, or go to the emergency department, if you notice:

• Vaginal bleeding or fluid leaking
• Regular tightening, cramping or pelvic pressure before your due date
• Severe or constant abdominal pain
• Sudden swelling of the face or hands, a severe headache, or changes in vision
• A noticeable decrease in your babies’ movements later in pregnancy
• A rapid increase in the size of your abdomen over a short time

Call 911 if you feel very unwell. A community imaging clinic is not set up for urgent pregnancy care.

Key takeaways

• An early ultrasound helps establish whether twins share a placenta, which shapes the rest of the care plan.
• Twins who share a placenta are generally followed more closely than twins with separate placentas.
• Extra scans are normal for multiples and focus on growth, fluid, blood flow, the cervix and position.
• Some scans may be done at a community clinic and others at a hospital or specialized unit, as your provider directs.
• Urgent symptoms always go to your provider or the emergency department, not to your next scan.

Booking an obstetrical ultrasound in Ajax

Rossland Diagnostic Clinic provides obstetrical scans as part of our ultrasound service at Unit 102, 300 Rossland Road East, Ajax, with free parking and ground-floor access. We are open Monday to Friday from 9:00am to 5:00pm and Saturday from 8:00am to 3:30pm. Bring your health card and requisition, and let us know it is a twin pregnancy when you call 905-426-3111 or request an appointment.