Ultrasound tracks twin growth

A new study is testing whether ultrasound during a twin pregnancy can detect potential growth problems When Mary Kelly felt exhausted in the early stages of pregnancy she put it down to having two older children

THEY CAN be double the trouble or twice the fun. But however you add them up, around one in every 50 pregnant mothers here will receive the news that she is expecting twins.

And now the largest study of its kind in Ireland is using ultrasound to look at how twins grow during pregnancy, with a view to identifying and heading off potentially dangerous problems.

In twin pregnancies there is a risk of one baby growing substantially less than the other, which, in severe cases, could result in the loss of both twins, explains Prof Fionnuala McAuliffe, a consultant obstetrician and maternal-foetal medicine expert at the National Maternity Hospital in Holles Street, Dublin.

That's why a consortium of eight maternity centres around the State is testing whether ultrasound scans during a twin pregnancy can effectively detect such problems early on and help improve the babies' chances of survival.

"We are looking to see if we scan regularly in pregnancy are we able to pick up these growth problems earlier and deal with them," says McAuliffe, who co-ordinates the research at the Holles Street site.

"The challenge is that if one baby is very healthy and doing nicely and one is in trouble, what do you do? How you manage the pregnancy can be quite complex because you have to think of two babies, one healthy one and one sick one."

Around two-thirds of twins are non-identical, where each baby has its own placenta (afterbirth) in the womb, so is plumbed in separately to the mother. Such "dichorionic" pregnancies are relatively low-risk for growth problems and are usually scanned once a month in the study, explains McAuliffe.

But sometimes even these non-identical twins can grow at substantially different rates. "One can be small and one can get large. It might just be that, by chance, one placenta gets a larger area to attach to the womb," she says.

The remaining one-third of twins are identical and share a single placenta. These "monochorionic" pregnancies are at greater risk of growth problems and are scanned fortnightly, according to McAuliffe.

One of the identical twins may get the lion's share of the single placenta, she says. "If you have one placenta that's dividing in two it isn't a 50-50 split. Sometimes one baby gets two-thirds and the other baby only gets a third from the beginning, so then it's destined that it gets a smaller share of the placenta."

Delivering just one baby is not an option, so the twins need to be carefully monitored, according to McAuliffe.

"If one baby has a growth problem there isn't really any medication we can give to make that twin grow, we just try to get that baby along until a stage where we think that baby and the co-twin will survive."

However, a more immediate risk crops up in around a quarter of identical twins, where one baby pumps blood into the other through shared blood vessels in the placenta in a condition called twin-twin transfusion syndrome, explains McAuliffe.

"Over time one baby gets fairly anaemic and is very small because it is not growing as much. If you have this severe twin-twin transfusion and you do nothing, then 90 per cent will miscarry. So you really are in a dire situation there.

"However, ultrasound can pick up the syndrome around 18 weeks into the pregnancy, and, where needed, doctors can perform in utero laser surgery to close off the problematic vessels, she notes. "With the laser surgery, survival is up to 70 per cent. There's a big improvement there. It's not 100 per cent but you are in a situation where if you do nothing the outcome is very poor."

The ultrasound study is run by Perinatal Ireland, a research consortium founded and chaired by consultant obstetrician Prof Fergal Malone, that encompasses the three public maternity hospitals in Dublin, as well as maternity units in Cork, Limerick, Drogheda, Galway and Belfast.

The Health Research Board-funded initiative has already scanned over 240 twin pregnancies and successfully picked up on growth issues and intervened where needed.

"It's too soon to look at the full effects but there's no doubt that we are picking up a lot of things with the regular scanning and detecting problems," says McAuliffe.

Dedicated team ensures peace of mind for parents

ANOTHER ADVANTAGE for expectant mothers on the twin study is that they are seen frequently through the pregnancy, and new twin clinics have been set up at some of the centres, according to Prof Fionnuala McAuliffe, a consultant obstetrician and maternal-foetal medicine expert at the National Maternity Hospital in Holles Street in Dublin.

"It means you have a dedicated team scanning and looking after them, and I think the patient benefits from that," she says.

When Mary Kelly felt exhausted in the early stages of pregnancy, she put it down to having two older children, and the demands of a busy job training teachers - as well as growing another baby.

But when she went for a routine scan at 13 weeks, she found out she was actually growing two babies.

"I think I screamed when they told me," she recalls, laughing.

"It was a complete surprise, I would never in my wildest dreams have thought I was expecting twins."

Under the care of Dr Michael Foley at Holles Street, she was offered a place on a new study that uses ultrasound to monitor the growth of twins in the womb during pregnancy.

"I hadn't been aware of the finer details, the growth complications that can happen with twins, but when I read up on it I wanted to go on the study as it would mean a bit more security and peace of mind," says Kelly.

Because her twins were identical and so at higher risk for growth problems, she went for fortnightly scans.

"Each scan took about half an hour," she says. "They measured the head, the tummy, the femur and looked at the placenta. And at the end they would give you a rough estimate of their weights."

Thankfully, Kelly's twins gave no cause for concern and, almost 37 weeks into the pregnancy, she delivered two healthy boys, Ciarán (5lbs 13oz) and Jack (5lbs 3oz), who are doing "fantastically well".

Life with twin newborns, a three- and a six-year-old is not as manic as Kelly had expected. "But we do have a very busy house," she says.