Embargoed: 00.01 hrs London time Thursday 25 ... - Oxford Journals

Embargoed: 00.01 hrs London time Thursday 25 May 2006
New research links placenta praevia directly to assisted reproductive techniques
Norwegian researchers have found the first evidence that techniques used in assisted
reproduction (ART) may be directly linked to an increase in placenta praevia – a
potentially dangerous condition in which the placenta covers, or partially covers the
cervix, blocking the baby’s passage into the birth canal.
A study published today (Thursday 25 May) in Human Reproduction 1 concluded that
there was a six-fold higher risk of the condition in single-baby pregnancies conceived
through ART compared with natural conception and a three-fold higher risk among
mothers who had conceived both naturally and through ART.
“What this means in absolute terms is that after adjusting for factors such as maternal
age, which tends to be higher in ART pregnancies, the risk of placenta praevia rose from
about three in 1,000 births to 16 in 1,000 births for ART pregnancies compared with the
general population, and from about seven in 1,000 births to 20 in 1,000 births for those
who had both assisted and natural conceptions,” said lead author Dr Liv Bente
Romundstad, from the Department of Obstetrics and Gynaecology at St Olavs University
Hospital in Trondheim.
Placenta praevia, where the placenta attaches itself to lowest segment of the uterine wall
and either blocks or partially blocks the cervix, is associated with serious and potentially
life-threatening problems for mother and baby. These include haemorrhage in the
mother, either in before or after the birth, and the need for caesarean section in the case
of total placenta praevia. For the baby the risks include prematurity and perinatal
problems.
Some small studies have suggested in the past that placenta praevia is more common
after ART, but the authors believe that the new research looking at over 845,300
pregnancies in the Norwegian Medical Birth Registry between 1988 and 2002 is the most
extensive in the world to examine links between placenta praevia and ART. Furthermore,
it is the first to indicate that the increase in risk may be directly related to the reproductive
techniques used.
Dr Romundstad explained: “As well as comparing placenta praevia among women who
had given birth only to babies conceived through IVF or ICSI 2 and the general population,
we studied 1,349 women who had conceived spontaneously in one pregnancy and after
assisted fertility in the other. Regardless of whether it was the first or second pregnancy
that was conceived through ART we found a nearly three-fold higher risk of placenta
praevia. This suggests that a substantial proportion of the extra risk may be attributable
directly to factors relating to the reproduction technology.”
The underlying mechanism causing the placenta praevia is not clear. One possibility
could be the position that the embryo is placed in the uterus when it is transferred via a
catheter through the cervix. The procedure may induce uterine contractions, possibly due
to the release of prostaglandins after stimulation of the cervix, leading to more embryos
implanting low-down in the uterus. In addition, because research has shown that
transferring the embryo to a position low in the uterus may improve implantation rates,
current practice tends to favour placing the embryo low down.

Their findings have so concerned the research team that they are calling for ART centres
to monitor and record the distance of every transferred embryo from both the internal
cervical entrance and the uterine fundus (the part of the uterus lying above the opening
of the fallopian tubes).
“We now routinely do this, but we need other centres worldwide to do this as well,“ said
Dr Romundstad. “Although the risk of placenta praevia is considerably higher with ART it
is still quite rare, which means it will probably take several thousand pregnancies to get
sufficient data to be able to make any definite recommendations about clinical practice.”
(ends)
1
Increased risk of placenta previa in pregnancies following IVF/ICSI; a comparison
of ART and non-ART pregnancies in the same mother. Human Reproduction.
http://www.oxfordjournals.org/eshre/press-release/freepdf/del153.pdf
2
I VF – in-vitro fertilisation. ICSI – intracytoplasmic sperm injection: process by which an
ooctye is fertilised by injecting a single sperm into the ooctye.
Notes:
PDF version of this press release and full embargoed text of the paper with complete results can be
found from 09:00hrs London time Tuesday 23 May at:
http://www.oxfordjournals.org/eshre/press-release/may06.pdf or is available from Margaret Willson
Human Reproduction is a monthly journal of the European Society of Human Reproduction and Embryology
(ESHRE). Dr Helen Beard, Managing Editor. Tel: +44 (0)1954 212404.
Email: beardh@humanreproduction.co.uk
ESHRE’s website is: http://www.eshre.com
Please acknowledge Human Reproduction as a source
Abstracts of other papers in ESHRE’s three journals: Human Reproduction, Molecular Human Reproduction
& Human Reproduction Update can be accessed post embargo from http://www.oxfordjournals.org/eshre
Papers available on request from Margaret Willson.
Contact (media inquiries only)
Margaret Willson: Tel: +44 (0)1536 772181. Mobile: +44 (0)7973 853347.
Email: m.willson@mwcommunications.org.uk