Improving baby safety by reducing multiple births - the HFEA calls for
The Multiple Births Foundation (MBF) welcomes the HFEA call for a
professionally-led, coordinated national strategy to reduce the number
of multiple births following fertility treatment.
The MBF provides
advice, information and support to multiple birth families and training
and education for professionals about their special needs and problems
and how to meet them.
Although there are many joys for these families,
far less well know are the higher risks for the mothers and babies.
Prematurity and low birth weight are the main reason for increased
mortality and disability for these children.
At the MBF we support
families in all circumstances. Sadly, much of this involves those who
are bereaved or caring for one or more children with cerebral palsy and
other health and developmental problems. We see the heart break and
life long suffering which is so often underestimated or forgotten by
professionals and the public.
With the increasingly reassuring evidence
that careful and individual selection of patients for single embryo
transfer can maintain good pregnancy rates, we strongly support the HFEA
proposal to develop the many facets of a strategy to reduce multiple
births which will have the confidence of all involved.
We look forward
to working with the HFEA, professional bodies and other organisations to
If you require more information
please contact the MBF offices.
Newly released statistics on Multiple Births in England and Wales for 2011 obtained from the Office of National Statistics:
Multiple Birth Rate/1000 mats
Monozygotic (MZ) (monozygous, uniovular, "identical")
arising from the splitting of a fertilised egg (zygote) during the
first 14 days after fertilisation. They have the same genetic make-up
(and therefore also the same sex).
Dizygotic (DZ) (dizygous, binovular, fraternal or "non-identical")
resulting from the fertilisation of two independently released ova
by two different sperm. There are equal numbers of same and unlike
sex pairs who are genetically no more alike than are any two siblings.
About 1/3 of twins in the UK are MZ and 2/3 DZ.
Whether the twins are MZ or DZ can be determined by analysis of
DNA samples from blood or other tissues. All unlike sex twins are
DZ. All monochorionic twins are MZ. Thus DNA analysis is required
for the approximate 50% of twins who are like sex with dichorionic
NB. More information about zygosity can be found on the ‘Are
they Identical?’ page on this website, the MBF also has a
leaflet we can send you, see publications page.
All DZ twins and one third of MZ twins have separate inner (amnion) and outer (chorion) sacs and are thus dichorionic, diamniotic. Two thirds of MZ twins have a single outer sac and two inner (monochorionic, diamniotic). About 1% of twins will share their inner sac (monochorionic, Monoamniotic).
MZ - causes still unknown. (There are slightly more than
expected sets resulting from infertility treatment (drugs alone
or IVF). The MZ twinning rate had been constant worldwide at about
3.5 per 1,000 maternities but there has been a slight rise recently.
DZ - the main factors associated with DZ twinning are infertility
treatment, race (highest in Black Africans and lowest in Orientals),
maternal age, parity, maternal height and weight and maternal family
history of twins.
and Higher Multiples
The largest surviving complete set is of septuplets (in US). Three
complete sets of sextuplets survive in the UK (6 girls in 1983,
3 boys and 3 girls in 1986 and 1 boy and 5 girls in 1993). The triplet
rate in the UK used to be about 1 in 10,000 maternities. This figure
more than quadrupled between 1970 and 1998 following the introduction
of ovulation induction and multiple embryo transfer in the treatment
of subfertility. The triplet rate has fallen annually since 1998
probably due to more judicious treatment for infertility including
a reduction in the maximum number of embryos that can be transferred
in an IVF cycle. Some further unrecorded triplet and higher order
pregnancies will have been reduced to twins or a single fetus by
medical intervention, referred to as multifetal pregnancy reduction,
early in the pregnancy.
The Human Fertilisation and
Embryology Authority (HFEA) national data for 1/4/2000 to 31/3/2001
showed that in the UK 1579 twins and 109 triplet births resulted
from IVF. The HFEA policy states that no more than 2 embryos should
be transferred in an IVF cycle except in exceptional circumstances.
There are no restrictions in the use of ovulation inducing drugs.
Three, Four and More, published by HMSO 1990. This national
study of triplet and higher order births included the obstetric,
paediatric and social aspects of all families with triplets and
higher order births born in the UK 1979 - 1986 (except 1981). A
new study is planned.
Average pregnancy length
- Singletons 40 weeks
- Twins 37 weeks
- Triplets 34 weeks
- Quadruplets 32 weeks
- Singletons 3.5kg
- Twins 2.5kg
- Triplets 1.8kg
- Quadruplets 1.4kg
Rates (England and Wales 2007)
The high rate amongst multiples
is largely due to their prematurity and low birthweight. Mortality
is higher in MZ than DZ twins mainly due to the 2/3 of MZ twins
with monochorionic placentas and a shared blood circulation. A higher
incidence of congenital abnormalities is another factor.
General development in twins (provided they have not suffered complications
from prematurity) is similar to singletons. The area most at risk
of delay is language. Twins
are more likely to be delayed in their language development; boys
more so than girls. Up to 40% of twins develop a twin language,
otherwise known as idioglossia or cryptophasia or "the secret
language of twins").
Disabilities of most kinds are more common in multiples
mainly, but not entirely, due to prematurity and low birthweight
Cerebral Palsy Rate per 1000
*Western Australia figures
Facts about Multiple Births
Special Needs in Twins and More
The First Five Years and Beyond
Individuality in Twins
Language Development in Twins
Relating to Twins
The Twin (and Triplet) with Special Needs
When a Twin or Triplet Dies
Twins, Triplets and More: Their Nature, Development and Care
by Elizabeth Bryan, Multiple Births Foundation, 1996.
Entwined Lives: Twins and What They Tell Us About Human Behavior by Nancy Segal, EP Dutton, 1999.
The Lone Twin: Understanding Twin Bereavement and Loss by Joan
Woodward, Free Association Books Ltd, 1998