The NHS has been told to improve its care of pregnant women carrying twins or triplets in order to reduce the significant medical risks involved for both mothers-to-be and their babies.

The National Institute for Health and Clinical Excellence, which sets standards for the NHS, has issued its first guidance on how health professionals should manage multiple births after discovering wide variations in the quality of care provided by different parts of the NHS.

Improvements and new procedures are needed in order to give women who conceive twins or triplets better and more consistent care, minimise the number of unnecessary caesarean deliveries among them and reduce the number of twins and triplets who require specialist care at birth.

About 11,000 women a year in England and Wales give birth to twins, triplets or, more rarely, four babies or more simultaneously. Multiple births account for 3% of the 700,000 live births a year.

The number of women giving birth to two or more babies at the same time rose from 10 per 1,000 in 1980 to 16 per 1,000 in 2009, mainly due to the increased use of assisted reproduction, especially IVF.

Mothers with a multiple pregnancy need specialist care in order to safeguard against the many problems and complications that can affect the mother or babies.

While many women carrying twins or triplets will experience a straightforward pregnancy, such patients are known to be at much greater risk of miscarriage, anaemia, hypertension, vaginal bleeding, premature birth and needing an assisted delivery or caesarean.

For example, while 4.8 per 1,000 of every pregnancy involving a single child end in stillbirth, 11.2 per 1,000 of those involving twins end in stillbirth, as do 27.9 per 1,000 of those involving triplets.

Babies of multiple births, meanwhile, are similarly at higher risk of poor outcomes including being born prematurely, having a low birthweight, admission to a neonatal intensive care unit, congenital malformations, cerebral palsy and impaired physical and cognitive development.

In its guidance released on Wednesday, Nice recommends that all women having an uncomplicated twin or triplet pregnancy should be cared for by a multidisciplinary team of medical experts who are experienced in such pregnancies, including obstetricians, midwives and ultrasonographers as well as a mental health professional, infant feeding specialist, dietitian and women's health physiotherapist.

They should also undergo a risk assessment before the birth to establish whether the babies are identical siblings, where they come from the same egg and share one placenta, or have a placenta each, and undergo careful management from then on.

Identical siblings in utero involve a much higher risk of stillbirth, foetal complications and a condition called twin to twin transfusion syndrome.

Woman carrying multiple foetuses should also be given ultrasound scans in the first three months, more antenatal visits and monitoring of their babies for signs of intrauterine growth restriction after they are 20 weeks' pregnant.

"We know there is a real clinical need for this guideline because NHS antenatal care for women expecting twins or triplets appears to vary considerably across England and Wales", said Dr Fergus Macbeth, the director of Nice's centre for clinical practice.

"For example, not all women with multiple pregnancies are cared for in dedicated settings such as 'twin clinics' or by multidisciplinary teams of healthcare professionals. This can lead to higher than necessary rates of assisted birth and caesarean sections and also means that women are not appropriately assessed for possible risks during pregnancy."

Macbeth added: "Although many women will have a normal pregnancy and birth, it is well known that there are higher risks involved for these types of pregnancy and so it is important to get it right. We hope this guideline will set the standard of high-quality care, which should be provided to all women pregnant with twins or triplets.

"Implementing these clear recommendations will help women to feel supported and well looked after at a time when they can be feeling anxious."

Keith Reed, chief executive of the charity Twins and Multiple Births Association (Tamba), said: "Sadly the care some expectant multiple birth mothers currently receive does not meet their needs. These important guidelines are a landmark in the antenatal care of multiples.

"They will undoubtedly produce better clinical outcomes as well as reducing anxiety for those women who have been told their pregnancies are 'high risk'."

Jane Denton, director of the Multiple Births Foundation, said the new standards would "transform" care.

"The news of a twin or triplet pregnancy is often a great shock for parents and the risk of complications during the pregnancy and preterm birth, as well as the practical and financial implications for the family, can cause great anxiety.

"Although much of the care at present is very good, there are many inconsistencies … these recommendations address all of these concerns and will give mothers confidence that they are receiving the highest standard of care.