Subfecundity and neonatal mortality: longitudinal study within the Dan
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《英国医生杂志》
1 Danish Epidemiology Science Centre, Department of Epidemiology and Social Medicine, University of ?rhus, ?rhus, Denmark (DK8000)
Correspondence to: O Basso bassoo2@niehs.nih.gov
Introduction
Mothers waiting for longer than one year to conceive their first child gave birth to babies with a higher risk of neonatal death compared with children conceived sooner. We restricted the analysis to primiparae (73.5% of whom reported no previous pregnancies) because death of a previous baby may influence both the decision to conceive again and its outcome.
Infertility treatment was self reported and was only asked of women taking longer than six months to conceive, but there was little difference in risk between treated and untreated, although the causes of death may differ between the two groups.
Only about 35% of eligible women participated in the cohort,5 and this could cause bias if participants with a long time to pregnancy were at a different level of risk compared to the non-participants. Furthermore, we could not distinguish the length of infertility beyond one year, which limits our ability to identify a dose-response, if it exists.
We collected information on time to pregnancy and confounders before delivery, reducing the potential for other types of bias. The mother's job title may be a poor proxy for social class, but the adjustment appeared to have little effect on our estimates.
A long time to pregnancy per se is not commonly considered a marker of increased risk, and untreated women with a history of infertility may seek (or receive) inadequate prenatal care.
Even though neonatal death was a rare event in this population, it is a serious outcome and any potential risk marker should be considered. Our finding needs, however, to be corroborated elsewhere before it can be stated that a long time to pregnancy increases the risk of neonatal death.
If infertility itself is associated with adverse outcomes, an appropriate comparison group should be used when assessing effect of infertility treatment on pregnancy outcomes, lest adverse effects of treatment be overestimated.
What is already known on this topic
Infertility treatment is correlated to adverse pregnancy outcomes, and evidence indicates that subfecundity per se is also associated with adverse pregnancy outcomes
What this study adds
Subfecundity may be associated with an increased risk of neonatal death and should be included as a risk indicator in neonatal care
This article was posted on bmj.com on 4 February 2005: http://bmj.com/cgi/doi/10.1136/bmj.38336.616806.8F
Contributiors: OB and JO had the idea for this study and formulated the hypothesis to be tested. OB analysed the data and both authors contributed to the interpretation of the findings. OB drafted the manuscript, and JO provided critical comments. JO is guarantor.
Funding: OB had a grant from the Danish Medical Research Council (No 22-00-0008). The Danish Epidemiology Science Centre was established by a grant from the Danish National Research Foundation. The Danish National Birth Cohort is funded by the Danish National Research Foundation, the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health Foundation.
Competing interests: None declared.
Ethical approval: National Scientific Ethics Committee.
References
Helmerhorst FM, Perquin DA, Donker D, Keirse MJ. Perinatal outcome of singletons and twins after assisted conception: a systematic review of controlled studies. BMJ 2004;328: 261.
Olivennes F, Rufat P, Andre B, Pourade A, Quiros MC, Frydman R. The increased risk of complication observed in singleton pregnancies resulting from in-vitro fertilization (IVF) does not seem to be related to the IVF method itself. Hum Reprod 1993;8: 1297-300.
Henriksen TB, Baird DD, Olsen J, Hedegaard M, Secher NJ, Wilcox AJ. Time to pregnancy and preterm delivery. Obstet Gynecol 1997;89: 594-9.
Basso O, Baird DD. Infertility and preterm delivery, birthweight, and Caesarean section: a study within the Danish national birth cohort. Hum Reprod 2003;18: 2478-84.
Olsen J, Melbye M, Olsen SF, Sorensen TI, Aaby P, Andersen AM, et al. The Danish national birth cohort: its background, structure and aim. Scand J Public Health 2001;29: 300-7.(Olga Basso, research associate professor)
Correspondence to: O Basso bassoo2@niehs.nih.gov
Introduction
Mothers waiting for longer than one year to conceive their first child gave birth to babies with a higher risk of neonatal death compared with children conceived sooner. We restricted the analysis to primiparae (73.5% of whom reported no previous pregnancies) because death of a previous baby may influence both the decision to conceive again and its outcome.
Infertility treatment was self reported and was only asked of women taking longer than six months to conceive, but there was little difference in risk between treated and untreated, although the causes of death may differ between the two groups.
Only about 35% of eligible women participated in the cohort,5 and this could cause bias if participants with a long time to pregnancy were at a different level of risk compared to the non-participants. Furthermore, we could not distinguish the length of infertility beyond one year, which limits our ability to identify a dose-response, if it exists.
We collected information on time to pregnancy and confounders before delivery, reducing the potential for other types of bias. The mother's job title may be a poor proxy for social class, but the adjustment appeared to have little effect on our estimates.
A long time to pregnancy per se is not commonly considered a marker of increased risk, and untreated women with a history of infertility may seek (or receive) inadequate prenatal care.
Even though neonatal death was a rare event in this population, it is a serious outcome and any potential risk marker should be considered. Our finding needs, however, to be corroborated elsewhere before it can be stated that a long time to pregnancy increases the risk of neonatal death.
If infertility itself is associated with adverse outcomes, an appropriate comparison group should be used when assessing effect of infertility treatment on pregnancy outcomes, lest adverse effects of treatment be overestimated.
What is already known on this topic
Infertility treatment is correlated to adverse pregnancy outcomes, and evidence indicates that subfecundity per se is also associated with adverse pregnancy outcomes
What this study adds
Subfecundity may be associated with an increased risk of neonatal death and should be included as a risk indicator in neonatal care
This article was posted on bmj.com on 4 February 2005: http://bmj.com/cgi/doi/10.1136/bmj.38336.616806.8F
Contributiors: OB and JO had the idea for this study and formulated the hypothesis to be tested. OB analysed the data and both authors contributed to the interpretation of the findings. OB drafted the manuscript, and JO provided critical comments. JO is guarantor.
Funding: OB had a grant from the Danish Medical Research Council (No 22-00-0008). The Danish Epidemiology Science Centre was established by a grant from the Danish National Research Foundation. The Danish National Birth Cohort is funded by the Danish National Research Foundation, the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health Foundation.
Competing interests: None declared.
Ethical approval: National Scientific Ethics Committee.
References
Helmerhorst FM, Perquin DA, Donker D, Keirse MJ. Perinatal outcome of singletons and twins after assisted conception: a systematic review of controlled studies. BMJ 2004;328: 261.
Olivennes F, Rufat P, Andre B, Pourade A, Quiros MC, Frydman R. The increased risk of complication observed in singleton pregnancies resulting from in-vitro fertilization (IVF) does not seem to be related to the IVF method itself. Hum Reprod 1993;8: 1297-300.
Henriksen TB, Baird DD, Olsen J, Hedegaard M, Secher NJ, Wilcox AJ. Time to pregnancy and preterm delivery. Obstet Gynecol 1997;89: 594-9.
Basso O, Baird DD. Infertility and preterm delivery, birthweight, and Caesarean section: a study within the Danish national birth cohort. Hum Reprod 2003;18: 2478-84.
Olsen J, Melbye M, Olsen SF, Sorensen TI, Aaby P, Andersen AM, et al. The Danish national birth cohort: its background, structure and aim. Scand J Public Health 2001;29: 300-7.(Olga Basso, research associate professor)