Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, GA, USA
1 To whom correspondence should be addressed at: Division of Reproductive Health, Centers for Disease Control and Prevention, Mailstop K-34, 4770 Buford Highway NE, Atlanta, GA 303413717, USA. e-mail: lschieve{at}cdc.gov
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Abstract |
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Key words: assisted reproduction/live birth/singleton birth/success rates
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Introduction |
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US ART registryrationale for presenting singleton live birth rates |
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The most recent report, covering ART procedures initiated in 2001, introduces singleton live birth rates (Table I) as an additional measure of success (Centers for Disease Control and Prevention, American Society for Reproductive Medicine, and Society for Assisted Reproductive Technology, 2003). We believe presentation of this specific rate will draw attention more directly to the need to consider optimal infant outcomes. It is well established that multiple birth infants have greatly increased risks for adverse health outcomes such as low birth weight, preterm delivery, infant death, and disability among survivors (Kiely, 1998
; Martin and Park, 1999
; Martin et al., 2002
; Pharoah, 2002
). Additionally, the relationship between ART and multiple birth among US infants has been well documented (Reynolds et al., 2003
). Despite concerted efforts by the medical community and infertility advocacy groups to focus attention on the risk for multiple birth and related sequelae via practice guidelines (American Society for Reproductive Medicine, 1999
) and education campaigns, the proportion of live birth deliveries that are multiple births among ART patients in the US has changed little since 1996 (Table II). While triplet and higher order multiples have decreased somewhat, the overall multiple birth rate has been stable and the proportion of twins has been stable or actually increased for some ART types.
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In counties such as the USA where insurance companies often do not cover infertility treatments, particularly ART, many patients may feel pressure to maximize the opportunity for live birth delivery by having multiple embryos transferred. Additionally, anecdotal reports suggest that if success is defined solely as live birth deliveries, some ART providers also may feel pressure to transfer multiple embryos in an effort to maximize their publicly reported success rates. This viewpoint has been elaborated in a recent debate in which several leaders in the field, including several past presidents of the Society for Assisted Reproductive Technology (SART), question the value of clinic-specific reporting at all. This viewpoint stems from the concern that reporting success in terms of total pregnancy and live birth rates is resulting in increased competition among ART clinics, with multiple gestation an unfortunate consequence (Grifo et al., 2001; Jones and Schnorr, 2001
). Indeed, in the USA, high-order embryo transfer is still common practice. In 2001, only 6% of ART cycles that used fresh, non-donor oocytes which progressed to the embryo transfer stage involved single embryo transfer. Approximately 66% of ART cycles involved the transfer of three or more embryos, 32% of cycles involved the transfer of four or more embryos, and 11% of cycles involved the transfer of five or more embryos (Figure 1).
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Feasibility of singleton success rate measure
The feasibility of collecting complete and accurate data to report singleton live birth rates is comparable with the feasibility of data collection for total live birth delivery rates. Pregnancy outcomes are reported for >99% of the pregnancies reported to the US ART Registry, and plurality at birth is reported for 100% of the live births reported. Additionally, results from on-site data validation chart reviews in a random sample of clinics reporting data to the registry reveal very low error rates (<1%) for plurality (Centers for Disease Control and Prevention, American Society for Reproductive Medicine, and Society for Assisted Reproductive Technology, 2003).
Singleton live birth rate can also be presented to the general public in a manner that plainly delineates the utility of this measure. There is clear biological plausibility for a direct treatment effect between the transfer of multiple embryos and multiple birth risk. Moreover, the association between ART and multiple birth is strong. In the USA, the proportion of ART infants born in a multiple birth (53%) is 18 times the proportion of multiple births in the general population (3%) (Wright et al., 2003). Additionally, as stated earlier, the increased risk for adverse sequalae among multiple births is dramatic, even when considering only twins versus singletons. Thus, the implications of multiple birth and the rationale for presenting singleton live births as opposed to (or at least in addition to) total live births in ART success rates reports can be easily conveyed to both lay and professional audiences.
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Adverse outcomes beyond multiple birth |
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We suggest that rather than incorporating preterm delivery risk into a success rate measure, it will be more informative to supplement ART success rate measures based on singleton live births with detailed analyses of the additional risks for adverse birth outcomes among ART singletons. Such analyses should include examination of risks within subgroups of ART patients based on demographic, pregnancy history, infertility diagnosis and underlying aetiological factors, such as reproductive tract infections, to the extent possible. A major challenge for such analyses is to obtain accurate and complete data on a population basis for classification of ART patients into meaningful subgroups. For example, diagnostic protocols can vary greatly from clinic to clinic, and therefore a reported diagnosis of, for example, male factor infertility or endometriosis will not necessarily represent the exact same grouping of patients at all ART clinics. Thus, all analyses must be presented in the appropriate context.
Recently, several studies have suggested the need to consider outcomes such as congenital anomalies, even among ART singletons (Ericson and Kallen, 2001; Hansen et al., 2002
). Tracking and reporting these outcomes among ART singletons as well as among multiples would be desirable. However, the feasibility of obtaining accurate and unbiased data must be carefully considered. As the numerator moves along the continuum from pregnancy to healthy child, it becomes increasingly difficult to collect complete and accurate data at the population level. The paramount barrier is that in many countries, including the USA, medical care often is not co-ordinated between infertility, obstetric and paediatric providers. In the USA, the responsibility for reporting ART success rate data rests with the infertility clinic that provided the ART treatment. These clinics do not typically provide care for patients beyond the first trimester of pregnancy. Thus, clinic personnel must work to track patients once they are released from the clinics care to ascertain the outcome of each pregnancy. Birth outcome data are primarily from parental report.
While studies demonstrate that birth occurrence, date of birth and birth weight can be reported accurately (Lederman and Paxton, 1998), maternal report for even severe birth defects has been shown to have low sensitivity (Rasmussen et al., 1990
). Thus, while we believe the current US system accurately captures data needed to assess outcomes such as multiple birth and low birth weight, it should not be used to evaluate birth defects. Population-based birth defects registries in the USA use a much more rigorous active surveillance methodology with multiple clinical sources of data (Lynberg and Edmonds, 1994
). To provide useful information, any system to collect birth defect data among ART births must be similarly designed (Schieve et al., 2000b
).
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Conclusion |
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References |
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