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How do I know if I'm pregnant with twins?

Fatigue can be more severe if you’re expecting multiple babies. Severe nausea and vomiting, due to the high levels of HCG hormones present, can also be a sign of twins. A Doppler may detect more than one heart beat. You may also notice that your stomach start to protrude sooner and a little further than what you expect. Watch for these signs if you are over 35 or have a family history of twins as both increase your odds of having twins.

In the past, most women didn't learn that they were pregnant with twins until they were in labour. Today, with modern techniques such as ultrasound such late surprises are rare. Couples typically discover they're having twins during a routine ultrasound, often done in the first trimester. Ultrasound testing is almost foolproof when it comes to diagnosing twins, but the greater the number of foetuses, the less accurate it becomes. 

It's possible to see twins (or multiples) on an ultrasound scan at around six weeks, although one baby may be missed at this early stage. Sometimes a heartbeat can be seen in one amniotic sac, but not in the other. A second heartbeat may be revealed in a rescan in a week or two, or the scan may show that one amniotic sac is growing while the other remains empty. This is a fairly common, naturally occurring event known as the vanishing twin syndrome, where twins are conceived but only one will develop and grow.

If your pregnancy is a result of a fertility treatment such as in vitro fertilisation (IVF), you will most likely have an ultrasound as early as four or five weeks into your pregnancy, since in most cases there will be more than one embryo implanted to ensure success.
If you find out that you're pregnant with twins, read these articles on twins development and kind of twins.

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