Think you might be pregnant with twins?

The routine use of ultrasound now means that women can find out early on in their pregnancy if they are carrying twins.

Typically the first scan happens at around 12 weeks pregnant, but in some situations an earlier scan may be done, especially if the women has undergone IVF or experienced miscarriage in previous pregnancies.

From a scan doctors can look at the development of the placenta and its membranes to see if they are identical or not. Non-identical (fraternal) twins develop their own placentas but identical ones can share, or have their own, depending on when the fertilised egg splits.

Because of the rise in earlier scans vanishing twin syndrome has also been discovered. This is when a woman conceives twins but one isn’t viable so it dies in utero. The vanishing twin is partially or completely absorbed by the mother or twin.

The expert view

Patrick O’Brien, spokesman for the Royal College of Obstetricians and Gynaecologists and a consultant obstetrician at the University College Hospital, London, says: “It’s virtually impossible for the woman to tell herself if she’s carrying twins so it’s based on the scan and the earliest is about six weeks of pregnancy.

Women may have an early scan if there’s a bit of bleeding or pain in early pregnancy or if they’ve had fertility treatment or a miscarriage before. “Vanishing twin syndrome is when you conceive twins but at a very early stage one fails to develop so that it just disappears. So you might see twins at an early scan but then later not; it’s more known about these days because women have such early scans. The disappearing twin occurs in the first eight to 10 weeks. It doesn’t seem to have any adverse effects on the remaining child as far as we can tell but there haven’t been any big, long term studies on it.”

A mum’s view

Louise Roche, mother to Anna and Emily, says: “I never really thought I’d have twins although my grandfather is a twin. I had a scan at nine weeks because I was suffering very badly from morning sickness and then they told me I was expecting twins. I already had a one year old so I was worrying about how I’d cope but my mum was with me and she was overjoyed so I quickly got excited too.”