Reader Question: Is It Possible to Only See One Baby on Ultrasound?
Tuesday August 5, 2008
Q. Heather asks, "Is it possible to be pregnant with twins and it show up as a single pregnancy on the ultrasound?"
A. It is possible early in pregnancy, although it's fairly uncommon. However, it definitely can happen -- it happened to me!
© 2008 Pamela Prindle Fierro, licensed to About.com, Inc.
I had an early pregnancy transvaginal ultrasound at seven weeks. Here is an actual photograph from that ultrasound. One healthy embryo was clearly identified and I went on my merry way through pregnancy. Then, several months later I went in for a routine twenty week ultrasound scan. Surprise! "You've got two!" (I'll never forget that moment of utter astonishment.)
What happened in this case was that my monozygotic twins were monochorionic, sharing a placenta and encased in a single chorion, the outer membrane of the sac. Basically they were so close together that one is shadowed behind the other. When viewed in a two dimenstional picture, all that is visible is the "top" twin.
So it is possible, just not very likely. Keep in mind that this picture is nearly fourteen years old; ultrasound technology has improved since then, and the rise in multiple births ensures that doctors and technicians are more adept at identifying multiples. Also, this was an ultrasound scan very early in pregnancy; I was only seven weeks along when this was taken. By twenty weeks it was exceedingly and unmistakably evident that there were twins, so a later ultrasound would be more reliable. There were also some other circumstances that kept the presence of twins from being revealed, including a lack of extreme symptoms such as nausea or fatigue and a rotating set of doctors so that no one person listened to the fetal heartbeat(s) more than once. I never measured large for gestational age, and I never had any of the common screenings that might raise a flag for multiples such as hCG or AFP.
Think You Might Be Having Twins?
• Twin Pregnancy Ultrasound Gallery
• Top Ten Signs of Twins
A. It is possible early in pregnancy, although it's fairly uncommon. However, it definitely can happen -- it happened to me!
© 2008 Pamela Prindle Fierro, licensed to About.com, Inc.
What happened in this case was that my monozygotic twins were monochorionic, sharing a placenta and encased in a single chorion, the outer membrane of the sac. Basically they were so close together that one is shadowed behind the other. When viewed in a two dimenstional picture, all that is visible is the "top" twin.
So it is possible, just not very likely. Keep in mind that this picture is nearly fourteen years old; ultrasound technology has improved since then, and the rise in multiple births ensures that doctors and technicians are more adept at identifying multiples. Also, this was an ultrasound scan very early in pregnancy; I was only seven weeks along when this was taken. By twenty weeks it was exceedingly and unmistakably evident that there were twins, so a later ultrasound would be more reliable. There were also some other circumstances that kept the presence of twins from being revealed, including a lack of extreme symptoms such as nausea or fatigue and a rotating set of doctors so that no one person listened to the fetal heartbeat(s) more than once. I never measured large for gestational age, and I never had any of the common screenings that might raise a flag for multiples such as hCG or AFP.
Think You Might Be Having Twins?
• Twin Pregnancy Ultrasound Gallery
• Top Ten Signs of Twins
I just had this happen to me. I had an early ultrasound (transvaginal) at 6w1d which showed 1 baby. 2 days ago (10w6d) I went for an ultrasound as part of the NT Scan and she said “Your having twins”. Obviously the first ultrasound missed one of the babies. I think if the ultrasound is very early they can miss one of the babies because they are so small at that point.
This happened to me, too, 4 years ago. I had a “regular” (not transvaginal) at 8 weeks, then was surprised at 20!
This happened to me. I am a twin and I had 2 ultrasounds, one at 9 wks and one at 16 wks and they didnt even look for twins. It was during my 22 wk ultrasound to find out the sex that we were shocked. There was definately 2 babies. I knew there was something different about this pregnancy considering I was in maternity clothes at 2 months.
I didn’t find out I was having twins until I was 27 weeks!!! I didn’t have a first trimester ultra sound. I did have one at 19 weeks, but apparently a baby was hiding. At 27 weeks I had another ultrasound to figure out why I was so big….SURPRISE…you’re having twins!!!
Me too! One of my little rascals was hiding during our 9 week ultrasound and gave us a big surprise at 21 weeks.
This happened to me as well. The doctor suspected two embryos when he did a transvaginal ultrasound at 7 weeks. He had us wait a week and a tech repeated the ultrasound and was convinced that she only saw one. We were so relieved because we already have a 2 year old. We discovered there were two at the 20 week ultrasound.