1 Department of Public Health Science and General Practice and 2 Department of Obstetrics and Gynecology, University Hospital of Oulu, Finland and 3 Department of Epidemiology and Public Health, Imperial College School of Medicine, London, UK
Dear Sir,
We wish to thank Dr Merlob and Dr Fisch for their interest in our article concerning neonatal outcome and congenital malformations after IVF (Koivurova et al., 2002). We would like to respond to two aspects they pointed out.
Firstly, they pointed out the fact that there were no major cardiac malformations in our study population of IVF neonates, though an excess of atrial and ventricular septal defects (ASD and VSD) were found. Unfortunately the size of our study population (n = 304 exposed and 569 unexposed) is too small to detect rare cardiac defects such as transposition of great vessels. The detected septal defects are, in contrast, reasonably common.
Secondly, they pointed out that we regarded congenital hypothyroidism as a malformation. In this we followed the classification of malformations by the Finnish Register of Congenital Malformations and Birth Defects. In most cases congenital hypothyroidism results from thyroidal aplasia or hypoplasia, which can be counted as a birth defect. We understand that the definitions of congenital malformations differ to some extent between countries. Furthermore, we consider the fact that there were two children with congenital hypothyroidism in the control group (2/569, 0.35%; 95% exact binomial confidence interval, 0.041.26) to give a relatively high prevalence but it is based on small numbers as indicated. The overall prevalence of this endocrinopathy is 1:3500 (0.03%) in Finland (Dunkel, 1998), the same magnitude as was presented by Dr Merlob and Dr Fisch in their Letter to the Editor. We suggest no further conclusions should be drawn concerning this matter.
As was similar in the Israeli results (Merlob and Fisch, 1995; Fisch et al., 1997
), the congenital malformation rate in our IVF population (6.6%) was markedly higher than in the general population (4.4%), with two very rare multiple malformations (amniotic band sequence and Goldenhar complex). Therefore, we share the concern over the safety of IVF technology regarding congenital malformations with Dr Merlob and Dr Fisch, and suggest that special attention should be focused on IVF children.
Notes
4 To whom correspondence should be addressed. E-mail: sari.koivurova{at}oulu.fi
References
Dunkel, L. (1998) Endokrinologia. In Raivio, K. and Siimes, M.A. (eds) Lastentaudit. Gummerus Kirjapaino Oy, Jyväskylä, 1, pp. 294295.
Fisch, B., Harel, L., Kaplan, B., Pinkas, H., Amit, S., Ovadia, J., Tardia, Y. and Merlob, P. (1997) Neonatal assessment of babies conceived by in vitro fertilization. J. Perinatol., 17, 473476.[Medline]
Koivurova, S., Hartikainen, A.-L., Gissler, M., Hemminki, E., Sovio, U., and Järvelin, M.-R. (2002) Neonatal outcome and congenital malformations in children born after in-vitro fertilization. Hum. Reprod. 17, 13911398.
Merlob, P. and Fisch, B. (1995) In vitro fertilization and rare congenital major malformations (abstract) Teratology, 52, 120.[ISI]