Twins - Pregnancy - Knowledge Area

Making the difference from the bottom up

TWINS & MULTIPLE PREGNANCIES

Here is some basic information about having multiple births - twins or more. Please remember, this is general advice and not to be used in place of information given by your GP or midwife.

For more information and support, visit the Twins & Multiple Births Association (TAMBA) , Twins UK and Multiple Births Foundation websites.

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The Basics

Here are some numbers - the incidence of multiple births in the UK, 2005:

All Pregnancies	715,556
Singletons	704,862
Twins	10,533
Triplets	159
Quads + (4+)	2
All Multiples	10,694
Percentage Rate	1.49%

That's about 1 in 67 pregnancies resulting in a multiple birth.

This has increased over the last 20 years, most likely due to the rise in fertility treatments, the increased survival rates of premature babies and women starting families later.

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What are the different types of Twins?

Monozygotic (MZ) - also known as asidentical or uniovular, but to us normal people, that's identical.

These occur when one fertilised egg splits early on in the pregnancy - within 13 days.
There are no known factors for why this happens but rates are constant worldwide - 3.5 per 1000 births.
MZ twins are always the same sex as the separation of the egg produces two genetically identical individuals.
Not inherited, except in rare cases.
Conjoined twins are MZ twins that have not completely split after 13-16 days.

Dizygotic (DZ) - also known as fraternal, binovular or non-identical.

These occur when the mother produces two or more eggs in the same menstrual cycle, but which are then fertilized separately.
Factors include ethnic origin (highest in Nigerians, lowest in Japanese), fertility treatment, increased maternal age (until late 30s), maternal height and weight, and the number of previous pregnancies.
Inherited through the maternal side of the family.
No more alike than other siblings and have an equal chance of being the same or different sexes.
A mother with one set of DZ twins is about 5 times more likely to have another set.

Multiple births higher than twins (triplets, quads etc) can be MZ or DZ or a mixture of both.

In the UK, 1/3 of twins are MZ and 2/3 are DZ.

How can you tell the difference?

All different sex twins are DZ, ie non-identical.
In same sex children, compare features such as hair, eye colour, ears, teeth, fingerprints - this is all easier in older children.
In babies, the placenta is helpful - there are 3 types - separate, fused or single.
Separate placentas often indicate DZ twins but MZ twins can have separate placentas if the egg splits in the first few days.
Fused placentas may occur when 2 separate ones become implanted close together - with either DZ or MZ twins - and may appear as one placenta.
Single placentas only occur in the case of MZ or identical twins.
DNA testing is 99% accurate - not generally available on the NHS but a private test can be done.

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How will I know I am having twins/multiple birth?

Ultrasound scans are the most likely way to discover. All areas carry them out routinely at 20 weeks, some areas at 12 weeks as well, or you can arrange a private scan at this time.

Very few women reach full term without knowing they are having more than one baby. You have more hormones going round so are more likely to be suffering from morning sickness, you'll be a lot bigger than mums with one baby and your midwife is likely to hear two heartbeats (or more!).

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Carrying Twins

Many mothers say being pregnant with twins is more tiring and harder. Not only are you carrying two babies, but an extra placenta and extra amniotic fluid, as well. This added weight means you are more likely to suffer from backache and fatigue. Your blood pressure may be higher too (this should be tested at all your ante-natal appointments).

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What are the risks?

Rates of still births are low, but there is an increased risk for multiple births:

0.57% for singletons
1.3% for twins
5.1% for triplets
10% for quads

There is a higher incidence of cerebral palsy in multiple births which is mainly attributable to higher levels of premature births and lower birth rates.

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How early might the babies be born?

-	Average length of pregnancy	Average weight at birth
Singletons	40 weeks	3.5kg
Twins	37 weeks	2.5kg
Triplets	34 weeks	1.8kg
Quads	32 weeks	1.4kg

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Twins & Labour

Caesarean sections are more likely with twins, but birth usually goes to plan with babies born naturally with head down.

They aren't always in the perfect position because of their limited space inside the womb. If one is lying across the uterus then a caesarean is essential, and if they are underweight then a c-section may be the least stressful way for them to be born.

With twins and multiple births you'll have extra monitoring and care throughout your pregnancy.

As they are likely to be smaller, twins often need special care when they are born.

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Breastfeeding Twins

The practical aspects of this can be tricky, but your body should produce as much milk as is required. This all depends on how hungry they are when you feed them and how well latched on they are.

You'll need to figure out if you feed them at the same time or separately, and how best to position them. You might find it helpful to express milk so someone else can help feed as well (good bonding for Daddy, too).

Bottle feeding is fine, but if you can breast feed you'll save a lot of time and money (washing, sterilising, buying equipment and formula) but do what feels right for you.

You should find you'll get plenty of help from your midwife or health visitor.

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Personal Experiences

Please do let us know about having twins or multiple babies if this is something you have experinced.

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