Finding out you are having twins, triplets or even quadruplets can be exciting, but it may also bring worries and concerns for you, your partner and family members. If you are expecting more than one baby, it is important that you are well prepared for the changes that will take place both during your pregnancy and after the babies' birth.
How common is multiple pregnancy?
A woman who is pregnant with two or more babies is known as a multiple pregnancy. In the UK about one in 80 births resulting from a natural conception is a multiple.
One in four births after IVF result in either twins or triplets. Twins account for about 1.5 per cent of all pregnancies.
The number of multiple pregnancies has increased dramatically in the last two decades in the UK and in many other developed countries across the world.
One reason for this increase is that older women are more likely to conceive a multiple pregnancy naturally than younger women.
Another, and probably more significant factor, is that 'older' couples are more likely to use fertility drugs and treatments such as IVF (in vitro fertilisation) to assist conception.
What are the different types of twins?
The most common is non-identical twins (also called dizygotic or fraternal).
The babies come from two different eggs (zygotes) and are fertilised by two different sperm. So they are genetically as similar as siblings from different pregnancies, and can be of different sexes.
Non-identical twins each have their own amniotic sac, and are described as dichorionic, diamniotic (DCDA).
A monochorionic pregnancy is a multiple pregnancy, most commonly a twin pregnancy, in which babies are dependent on a single, shared placenta.
Approximately 30% of twin pregnancies in the UK are monochorionic. With identical twins, one egg from the mother is fertilised by one sperm from the father, and then very early in development the embryo splits and two foetuses grow.
Also called monozygotic where, each baby has the same genetic information. Usually identical twins each have their own sac of fluid (amniotic sac) and are called diamniotic (DA).
Rarely both babies are in the same single amniotic sac, and are called monoamniotic (MA).
What schedule of care will I receive?
You will be booked for shared care between community midwives and an obstetrician.
To be sure that any complications are detected and treated as soon as possible, you will be seen more frequently than in a singleton (single baby) pregnancy.
Women expecting twins or triplets will be offered more scans than women having a single baby. You may be referred to a Fetal Medicine Unit.
Your doctor (obstetrician) will recommend you deliver your babies in the hospital, to have access to doctors and resources (such as the special care baby unit), if they are needed.
How often will I be scanned?
Women expecting twins or triplets will be offered more scans than women having a single baby.
If your first scan shows you are having twins or triplets, the sonographer will check to see whether they share a placenta or not. This is because babies who share a placenta can have a higher risk of problems during the pregnancy.
You will be offered extra scans later in your pregnancy to check how your babies are growing. If your babies share a placenta, you will probably be offered growth scans more often than if they each have their own placenta.
When you're having identical twins, you will be offered more frequent ultrasound scans from 16 weeks.
If you are having non-identical twins you will have more regular scans from 28 weeks, to observe the babies growth and levels of amniotic fluid around each baby. So there will be plenty of opportunity to ask more questions of the doctors and midwives.
Very rarely, twins or triplets will also be in the same amniotic sac. If this happens, you'll be looked after by an obstetrician who has lots of experience looking after women with this kind of pregnancy.