“Do you see what I see?”
I was a resident in my fourth year of training in Obstetrics and Gynecology when these words were spoken by a radiologist doing my ultrasound. And, yes, I could see the two sacs and the two heartbeats on the screen. Twins!
As a parent of multiples, I know the excitement that comes with such news; as an obstetrician, I also know the extra cares and concerns that accompany that joy.
While you shouldn’t be needlessly alarmed, you need to know that some pregnancy complications are more common in women carrying twins, including:
- Nausea and vomiting
- Birth defects
- Lower birth weights for the babies
- High blood pressure during your pregnancy
- Early delivery (both because of spontaneous labor or the development of complications)
- Additional bleeding during delivery
I spend a lot of time talking with mothers of twins and more about these complications. The amount of information can be overwhelming, so I often break it down by gestational age with my patients. There is no point in worrying over something that is probably weeks away from happening.
In this post, I will address some of the most common questions that relate to the first trimester, and clarify some misconceptions.
Identical or fraternal? One placenta or two?
It’s important to try to distinguish what type of twin pregnancy you have, because potential pregnancy complications change depending on that information. More specifically, complications are different depending on whether there is one placenta shared by the two babies, or if each baby is in its own sac with its own placenta.
Your family history may help us determine if the twins are fraternal (two eggs are fertilized) or identical (one egg is fertilized and then splits after fertilization). Fraternal twins run in families. In some populations, as many as one in 20 pregnancies may be a twin pregnancy. Identical twins occur in one in 250 pregnancies, a statistic that is pretty constant around the world.
Other factors that influence your chance for fraternal twins include fertility treatments, older age, and increased body mass index. Patients who have had a fertility treatment that involved more than one egg often assume their twins must be fraternal. That’s not true. Patients who undergo fertility treatment also have an increased chance of identical twins.
The best way to determine the type of twin gestation is a first trimester ultrasound.
In the picture with this post, you can see what early ultrasounds look like for different types of twins. On the top image, the arrow points to a very thick membrane between the two sacs; this is how a pregnancy with two separate sacs and two separate placentas appears. However, identical twins that split within the first 72 hours after fertilization will look exactly the same as fraternal twins on ultrasound. Sometimes, in the case of two boys or two girls, we won’t know for sure until after the babies are born and we do further testing.
In the bottom image, the arrow points to a very thin white line between the two sacs, indicating identical twins that are in separate sacs sharing one placenta. Occasionally we won’t be able to see a dividing line or membrane which tells us the identical twins are together in the same sac.
Eat well, take supplements
We want you to gain more weight with twins – 40 to 50 pounds over the course of the pregnancy, compared with the 25 to 35 pounds we expect a woman with a normal BMI to gain. Like all pregnant women, you’ll also need to take an iron supplement to prevent anemia. But this is especially important in women carrying multiples since the risk of anemia and blood loss at delivery is higher. Hopefully you’ve been taking a folate supplement before getting pregnant; you’ll want to continue this as well to help prevent anemia.
I know from experience that thinking about eating and taking vitamins and supplements can be hard to do in the first trimester. From the beginning of my pregnancy carrying twins, I suffered from bad nausea and vomiting. Excessive nausea and vomiting can be associated with other pregnancy abnormalities, so I thought this might be the cause for my illness. Fortunately, I had another, much nicer reason for being extra sick! Check out Dr. Nelson’s suggestions to help manage morning sickness symptoms. And know that in the event of severe morning sickness more powerful drugs may be necessary to control your symptoms.
Down syndrome screening
All pregnant patients seen in their first trimester of pregnancy should think carefully about Down syndrome screening. But screening and diagnostic testing become more complicated with two fetuses, so you need to talk with your obstetrician about options. It’s also possible only one baby could be affected, making further decisions regarding the pregnancy difficult.
Coming next week
You’ve made it through the first trimester of your multiples pregnancy. What’s next? We’ll talk about ultrasounds, screening for birth defects, and the possibility of an early delivery in next week’s post on the Your Pregnancy Matters blog.