You may have heard of the ‘vanishing twin’ syndrome. This happens when one of the embryos fails to survive and is absorbed by the other. But have you heard of an ‘appearing twin’? How can a second baby magically appear? Parents will either be pleasantly surprised at the prospect of another child or be unprepared to look after two children. In this article, we take a look at possible causes of undetected twins.
Undetected twin: Ultrasound misses out the second gestational sac
This usually can happen when women go for their first ultrasound too early on in their pregnancy. Statistics show that an ultrasound between 5 and 6 weeks can’t reveal the second twin 14% of the time. This is especially true for identical twins who share a placenta. Most people think that all ultrasound scans are 100% accurate and doctors fail to mention that during early pregnancy, there is a higher chance to miss out important information. Going for the first ultrasound scan after six weeks can tell the parents much more about the pregnancy. If there are two gestational sacs, both heartbeats should be visible by then.
Undetected twin: Getting pregnant while already pregnant
This is a rare occurrence and only one case occurs each year in the world. This can happen when a woman ovulates more than once during a menstrual cycle. She can get pregnant both times if sperms are present. The gestational age will be different for the babies, usually about one or two weeks apart. In even rarer cases, ovulation does not stop during pregnancy and a woman can get pregnant even later on during her pregnancy. This was the case for a married couple in the UK. They had twins, but one was around five to six weeks older than the undetected twin. Doctors warned that the second baby was not likely to survive. But to the parents’ amazement, both babies were born perfectly healthy. In such cases, the infants born are not technically twins. They will look different and grow up at different speeds.
Cases of undetected twins may be rare but for assisted pregnancies and IVF pregnancies, possibilities of twins are higher. For most parents, the surprise of having a second child is a wonderful one.
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