Neurological sequelae in twins born after assisted conception: controlled national cohort study

In a recent study (ref 1) twins born in Denmark between 1995 and 2000
as a result of IVF/ICSI were found to be no more likely than naturally-
conceived twins to suffer from neurological morbidity. This is a very
important result which will go some way to allaying the fears of parents
of IVF/ICSI parents and clinicians. Nonetheless, as the editorial points
out (ref 2), the issue of multiplicity and it’s associated morbidity
remains.

Using data from the year 2000, we estimate that around 930 twin
babies were born alive in Denmark following IVF/ICSI treatment (ref 3),
representing 37% of the total 2540 twin babies born alive that year (ref
4). Using a risk estimate of 9.6 per 1000 for neurological morbidity in
any twin, the estimated number of cases of neurological morbidity in all
Danish twins born alive in 2000 is 25, approximately 9 (37%) of whom would
have been conceived by IVF/ISCI. Some of these 9 cases could have been
prevented if the IVF/ICSI twins had been born as singletons. The exact
number of "saveable" cases will depend on the risk in IVF/ICSI singleton
babies compared to naturally conceived singleton babies, an issue which
requires further clarification, but the fact remains that at least some
cases could be avoided each year.

The message is simple: high rates of multiplicity in babies resulting
from assisted conception continue to drive an excess health burden in the
population which is preventable. As long ago as 1990, multiplicity was
highlighted as the primary adverse health outcome in a study of the first
1500 babies born following IVF in the UK (ref 5). While there is evidence
that the frequency of higher order births (triplets and above) has now
started to decline in the UK (ref 6),there is as yet no similar evidence
for twinning rates.The excess morbidity associated with assisted
conception through multiplicity alone is thus likely to continue for some
time.

1 Pinborg A, Loft A, Schmidt L, Greisen G, Rasmussen S, Andersen AN.
Neurological sequelae in twins born after assisted conception: controlled
national cohort study. BMJ 2004;329(7461):311.

2 Keirse MJNC, Helmerhorst FM. How many eggs? BMJ 2004;329:302-3.

3 Nyboe Andersen A, Gianaroli L, Nygren KG; European IVF-monitoring
programme; European Society of Human Reproduction and Embryology. Assisted
reproductive technology in Europe, 2000. Results generated from European
registers by ESHRE. Hum Reprod 2004;19(3):490-503.

4. Data from Danish National Board of Health, Copenhagen.

5 Beral V, Doyle P. Births in Great Britain resulting from in-vitro
fertilization 1978-87. BMJ 1990;300:1229-1233.

6 Simmons R, Doyle P, Maconochie N. Dramatic reduction in triplet and
higher order births in England and Wales. BJOG 2004;111(8):856-8.

Competing interests:
None declared