When Do Twins Begin to Be Detected by Ultrasound?

Ultrasound is known to be useful for determining gestational age and ensuring that the growth and development of the fetus is appropriate for its age. Besides, it can also be used to detect whether you are pregnant with twins. As a future mother, you may be wondering when twins can be detected by ultrasound. Aside from that, you may also want to know what it means if twins cannot be detected during this test. If you want to find out the answers to these questions, check the full explanation below.

When Can Twins Be Detected by Ultrasound?

ultrasound photo of twins 1
Ultrasound Photo of Closely Spaced Twins
ultrasound photo of twins facing each other
Ultrasound Photo of Twins Facing Each Other

Generally, there are a few early signs that might indicate your chances of having twins, such as more severe morning sickness, extreme breast tenderness, and rapid weight gain. However, there is no guarantee that you are carrying twins until you check your pregnancy with ultrasound in the first trimester.

Read also: How Many Times Do Pregnant Women Have to Do Ultrasound?

In general, there are three ways to do ultrasound: transvaginal ultrasound (through the vagina), 3-dimensional ultrasound and 4-dimensional ultrasound, which can show the movement and figure of the fetus more clearly through video.

The first ultrasound can generally be done from 6-8 weeks of gestation. Through this test, you will be able to listen to the heart rate of the baby. Not only can you find the condition of the fetus, but can also diagnose pregnancy problems, because the obstetrician can also see the condition of your placenta and amniotic fluid.

As a pregnant woman, you may want to know the best time to do an ultrasound to detect twins. According to obstetricians, the best time to do it is at the age of 10-12 weeks of pregnancy. From the test, you can also find out the number of twins in the womb and whether your children are identical or fraternal twins. However, if you want to find out the sex of the baby, you can do an ultrasound at the age of 18 weeks of gestation. Actually, twin pregnancies can also be detected earlier through a blood test.

Why Can’t Twins Be Detected by Ultrasound?

In some rare cases, twin pregnancies may be detected later than that or even not detected at all until the mother finally gives birth to a pair of twins. There are a few reasons why twins are not being detected by ultrasound, such as:

1. Early Ultrasound Test

The first ultrasound is recommended from the first trimester to ensure pregnancy after getting a positive result from the test pack. However, from this test, you will not be able to detect whether you are actually pregnant with twins. If you do a transvaginal ultrasound at 6-7 weeks of gestation, you may only see one fetus even though there are two of them in the uterus. The earlier the ultrasound is done, the more inaccurate the results can be. It is because at this young gestational age the size of the fetus is still very small and the heartbeat is also not very clear. It is the thing that makes a twin pregnancy look like the pregnancy of one child. If you want to make sure whether you are pregnant with twins, it is better for you to do an ultrasound when the pregnancy is entering the second trimester. In general, twin pregnancies can be detected clearly by ultrasound starting at 10-12 weeks of gestation.

2. The Baby is in an Amniotic Sac

The development of twin pregnancies can be identical or non-identical twins (fraternal twins). The fraternal twin pregnancies are the ones that are easier to detect because each baby is in a separate amniotic sac. As for the identical twin pregnancies, only one amniotic fluid can be seen because the babies grow in the same amniotic sac.

3. Twin Babies Are Hiding

One of the reasons why twins are not detected by ultrasound is because the position of the babies is completely hidden and cannot be seen. This kind of case is known as hidden twins. For instance, the baby hides behind its siblings or ducks in one of the cranial corners of the uterus. This kind of condition makes the doctors have a hard time seeing twins.

4. Lack of Pregnancy Checkups

It will be necessary for you to check your obstetrics and undergo routine antenatal care once your doctor confirms you are pregnant. It should be done, especially because twin pregnancies are more complicated and risky. Remember that doing one ultrasound test may not be enough to know the condition and development of the baby until the time of the delivery.

As stated before, it is possible for multiple pregnancies to not be detected right away at the first visit. In other cases, the certainty of twin pregnancy may be known too late because of the different position of the babies. If you are a pregnant woman and rarely do obstetric checks, you may be aware late of pregnancy complications that might affect one of the twins, such as a failed fetus to thrive or IUGR or twin to twin transfusion syndrome or TTTS. Therefore, it is better for you to schedule more frequent appointments with your obstetrician even if you feel that your pregnancy is fine. In addition, you should also check yourself if you experience something bad during pregnancy that interferes with your daily activities.

5. Inadequate Medical Facilities and Personnel

In addition to some of the general things above, twin pregnancies may go undetected because the health center facilities are incomplete so that the ultrasound readings are not that clear. Sometimes, it is also due to the medical personnel who may be inaccurate in reading or interpreting the results of the ultrasound so that the twins are not seen. Generally, doctors can be 99% sure that you are pregnant with twins after doing an ultrasound at the age of 20 weeks of gestation and above. The reason is because the growth of each fetus is getting bigger.

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