1 Centre de Recherche en Biologie de la Reproduction (CRBR), Department of Obstetrics and Gynecology, Laval University and Ontogeny and Reproduction Research Unit, CHUL Research Center, T1 49, CHUL/CHUQ, 2705 Boul. Laurier, Québec, Canada, QC G1V 4G2. e-mail: ray.lambert{at}crchul.ulaval.ca
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Abstract |
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Key words: aetiology/assisted reproductive technologies/health problems/singleton pregnancies
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Introduction |
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Previously, we discussed the responsible conduct of research and the responsible practice of reproductive medicine regarding multiple gestations resulting from the transfer of multiple IVF/ICSI embryos (Lambert, 2002). Considering the existence of safer techniques and in total agreement with the opinion of ESHRE (ESHRE Campus Course Report, 2001
), the transfer of a single embryo was proposed as the solution to these multiple pregnancies.
In this line of thinking, the question of causality of health problems in singleton ART babies is critical for the proper treatment of infertility. Indeed, if infertility itself is the causative factor of these complications, then "...providing assisted reproductive technology to couples who are not really infertile will involve stress, time and money, but the costs will not include an excess rate of low birth weight or birth defects" (Mitchell, 2002). A gynaecologist could be proactive by trying to identify at-risk patients in order to provide a treatment to the least risky patients. However, if iatrogenic risks are involved, then the use of the in-vitro procedure or drugs "...for couples who are not infertile would result in unfortunateand avoidableexcess risks of low birth weight and birth defects" (Mitchell, 2002
). A prudent attitude would then be to adjust the procedure in order to reduce the complications.
Three possible sources of the increased risks of health problems in singleton ART babies are known: the in-vitro procedure, drugs to stimulate follicular development and ovulation and infertility itself. In order to discriminate between each of these factors and to establish their contribution to the aetiology of these problems, the following reasoning was held: (i) If the in-vitro procedure is involved, its role would be demonstrated by comparing the IVF group of singleton infants to a matched control group treated with ovarian stimulatory drugs without IVF. (ii) If ovarian stimulatory drugs are the causative factor, a difference in the outcome of pregnancies resulting from the use of these drugs as compared to spontaneous pregnancies would be observed. And, (iii) since artificial insemination (AI) with donor semen (AID/DI) is performed when a male factor is diagnosed, DI should not result in health problems for singleton infants if female infertility is the causing factor. On the other hand, AI with the partners semen in infertile or sub-fertile women would result in these health problems.
This rationale was tested by scrutinizing publications on premature birth, low birth weight, perinatal mortality and major birth defects which are all shown to be increased in singleton children born from infertility treatment. A PubMed search was thus performed using the following search profiles: IVF OR ICSI combined with either malformation*, prematurity, low birth weight, perinatal mortality or malformation AND singleton. This search was limited to publications written in English and published between 1998 and 2003. A total of 84 articles came out of the search usingmalformation*as keyword, 50 when prematurity was used, 37 were associated with low birth weight 33 with perinatal mortalityand 14 with malformation AND singleton. Of these numbers, only 15, 11, 12, 8 and 4 respectively dealt specifically with singleton pregnancies. An additional PubMed search was conducted using AID OR AI with each of the search terms used for IVF OR ICSI. This yielded one additional pertinent article. There was some overlap in the results of the searches and with the papers mentioned above so that we ended with a total of 29 publications dealing directly with singleton pregnancies. Only publications containing a matched control group were retained for further analysis (n = 14). Thus, papers that limited the comparison between IVF and ICSI were excluded from the present analysis.
Our literature search identified six original papers and a review (Olivennes et al., 2002) that compared the perinatal outcome of IVF pregnancies to matched group of naturally conceived gestations. Two did not show any differences between groups in terms of congenital malformations (Ericson and Källén, 2001
; Anthony et al., 2002
while four described significant or suggestive tendencies either for congenital malformations (Koivurova et al., 2002
; Strömberg et al., 2002
), prematurity (Dhont et al., 1999
; Perri et al., 2001
; Koivurova et al., 2002
;), low birth weight (Dhont et al., 1999
; Perri et al., 2001
; Koivurova et al., 2002
), cerebral palsy (Strömberg et al., 2002
) or developmental delay (Strömberg et al., 2002
). All studies involving matched spontaneous pregnancies (n = 7) which were reported in the review (Olivennes et al., 2002
) showed higher risks of prematurity and lower birth weight. Therefore, the effects of IVF treatment on congenital malformations are still controversial, but other adverse effects on the health of the resulting child are largely supported by the literature.
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The in-vitro procedure as a possible causal factor |
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Since this early demonstration, the large-fetal syndrome has been documented in sheep and bovine (Walker et al., 1992). It has been observed in offspring conceived in-vitro following in-vitro or in-vivo maturation of animal ova. It can also result from in-vitro culture of animal embryos. For instance, incubation media used for in-vitro culture of embryos and asynchronous transfer of embryos (Leese et al., 1998
) could induce epigenetic modifications during embryonic development (Wrenzycki et al., 2001
;De Rycke et al., 2002
; Thompson et al., 2002
;) and lead to the pathology. Musculoskeletal, cardiovascular and cerebral anomalies are characteristic of the syndrome (reviewed by Kruip et al., 2000
) and the humans seem to be at risk (De Rycke et al., 2002
; Thompson et al., 2002
). The first evidences suggesting an association between ART procedures and epigenetic alterations leading to congenital malformations syndromes in humans came recently from the studies on the Angelman (Cox et al., 2002
) and BeckwithWiedemann (DeBaun et al., 2003
; Maher et al., 2003
) syndromes. Being specifically associated with overgrowth similar to the large offspring syndrome reported in domestic animals, the risk factor for the BeckwithWiedemann syndrome would be around 6-fold in ART children as compared with the general population (DeBaun et al., 2003
; Maher et al., 2003
). Therefore, the in-vitro procedure is the most likely candidate to explain the health problems in singleton ART babies.
However, once the outcome of IVF pregnancies is compared to the outcome of pregnancies produced following insemination with the partners semen, the risks appear to be higher in the latter group (Nuojua-Huttunen et al., 1999). In both groups of patients, drugs for ovarian stimulation were prescribed and in both groups partners semen was used. Both groups are distinguished, however, by a tenuous difference: laboratory manipulations are brief and simple when a semen sample is prepared for AI, while these manipulations require a few days, from preconception to in-utero transfer in an IVF programme. Lower risks in the insemination group would have suggested an in-vitro procedure effect. Since the opposite tendency has been observed, the in-vitro procedure may not account for the increased risks of health problems in singleton babies born from ART.
Two other examples support this assertion. Women treated with ovulation stimulatory agents and inseminated with their partners semen leads to a higher proportion of low birth weight and perinatal mortality as compared with spontaneous gestations in women with a similar social profile (Nuojua-Huttunen et al., 1999). Since the two most important aspects distinguishing these groups of patients are infertility and ovarian stimulatory drugs, the trend suggests that either or both of these factors are at the origin of the increased complications. Finally, after adjustment for the effect of multiple pregnancy, IVF or gamete intra-Fallopian transfer (GIFT) babies do not seem to be at a more frequent risk of perinatal death than infertile women treated by drugs alone (Draper et al., 1999
). Again, this supports an absence of effect of the in-vitro procedure. However, the low power (small cohort) of these studies did not allow the findings to reach statistical significance.
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Drugs for ovarian stimulation as a possible causal factor |
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Infertility as a possible causal factor |
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Some maternal characteristics such as age and infertility are important risk factors (Bergh et al., 1999; Olivennes et al., 2002
). It is known that couples followed for infertility do reproduce at a later age: at least 50% are over 35 years old (Society for Assisted Reproductive Technology and American Society for Reproductive Medicine, 2002
).
A population-based casecontrol study has shown that, after adjusting for the effects of confounders, untreated infertility is 3.3 times more likely to have a perinatal death as compared to fertile women (Draper et al., 1999).
A recent study has shown that singleton infants born after AI using the partners semen were at a higher risk of low birth weight and prematurity than infants born after DI (Gaudoin et al., 2003). Although this study was not planned to include a matched control group, it compares two groups with similar profiles, AI and AID. The significant association between a partners AI (female infertility) and low birth weight combined with an absence of association between AID (male infertility) and low birth weight strongly support the notion that infertility might be involved as a causative factor for the poor perinatal outcome observed in ART children.
After our analysis of publications comparing groups with a comparable profile, we suggest that the in-vitro procedure and ovarian drugs are unlikely to be the causative factors of increased premature birth, low birth weight, perinatal mortality and major birth defects described in ART babies. On the other hand, our analysis clearly points out that the increased risks are intrinsically related to the health status of the infertile woman, thus confirming a long-awaited apprehension (Williams et al., 1991). A list of converging examples supporting this interpretation is presented in Table I.
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If this interpretation is right, the prudent attitude would be to identify at-risk women among an infertile population of women in order to preferentially offer a treatment to those showing the best prognosis. To our knowledge, such population-based studies have not yet been performed. Therefore, criteria permitting identification of at-risk patients are not available at the moment. There is an urgency in the field to identify these criteria so that gynaecologists will offer a treatment only to low risk patients.
Epigenetic alterations resulting in retinoblastoma (Moll et al., 2003), congenital malformations and overweight babies (DeBaun et al., 2003
; Maher et al., 2003
) seem to be at a higher incidence in ART babies. Although some of these abnormalities have been attributed to the procedure (DeBaun et al., 2003
), support for this hypothesis is fragile for the moment. Rather, the very few papers (Draper et al., 1999
; Nuojua-Huttunen et al., 1999
) surveyed in the present PubMed search that deal with this matter suggest that factors other than the procedure are involved. The possible association between some types of congenital malformations and ART may be related to multiple pregnancies, to the use of ovarian stimulatory drugs or to infertility itself as well as to the in-vitro procedure. The small number of patients and the design of the studies reported here do not allow distinction between each of these hypothetical causative factors. An analysis of the frequency of BeckwithWiedemann and Angelman syndromes in an artificially inseminated population of patients compared to the IVF group of patients would help to resolve this issue.
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Conclusion |
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Acknowledgement |
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References |
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