Measuring perinatal complications: methodologic issues related to gestational age

<p>Abstract</p> <p>Background</p> <p>Perinatal outcomes differ by week of gestational age. However, it appears that how measures to examine these outcomes vary among various studies. The current paper explores how perinatal complications are reported and how they might differ when different denominators, numerators, and comparison groups are utilized.</p> <p>Conclusion</p> <p>One issue that can clearly affect absolute rates and trends is how groups of women are categorized by their gestational age. Since most perinatal outcomes can only occur in women and neonates who have delivered, using the number of pregnancies delivered (PD) as the denominator of outcomes is appropriate. However, for an outcome such as antepartum stillbirth, all women who are pregnant at a particular gestational age are at risk. Thus, the denominator should include all ongoing pregnancies (OP). When gestational age is used by week this means using both deliveries during a particular week plus those women who deliver beyond the particular week of gestation in the denominator. Researchers should be careful to make sure they are utilizing the appropriate measure of perinatal complications so they do not report findings that would be misleading to clinicians, patients, and policy makers.</p

The risk factors for unexplained antepartum stillbirths in Scotland, 1994 to 2003

Objective: To determine the factors contributing to unexplained antepartum stillbirth in Scotland. Study Design: A 10-year birth database in Scotland was used to compare the unexplained antepartum stillbirth with other birth outcomes. The sample unit was a pregnant mother with a gestational age of 20 weeks and above and with a fetal birth weight of 200 g and above. Result: Maternal age of 35 years and above, lower deprivation category, inaccessible area of residence, maternal smoking, maternal height of <160 cm and gestational age of above 39 weeks were significantly associated with unexplained antepartum stillbirth. In multivariable analysis only maternal age (adjusted odds ratio (OR): 1.8, confidence interval (CI): 1.1 to 3.0, P=0.02), smoking during pregnancy (adjusted OR: 2.0, CI: 1.1 to 3.5, P=0.02), and maternal height (adjusted OR: 1.4, CI: 1.1 to 1.8, P=0.01), remain significant. Screening of pregnancies based on these three risk factors had 4.2% sensitivity and 99.4% specificity. The prevalence of stillbirth for this population was 0.2%. A positive predictive value of only 1.2% implies that only 1 in 83 women with these three risk factors will have antepartum stillbirth. The remaining 82 will suffer needless anxiety and potentially diagnostic procedures. Conclusion: Advanced maternal age, maternal smoking, and shorter maternal height were associated risk for unexplained antepartum stillbirth but screening based on these factors would be of limited value

Obstetricians say yes to maternal request for elective caesarean section: a survey of current opinion

Aim: To determine what proportion of obstetricians would agree to elective pre-labour CS for;maternal request'. Methods: Every fifth consultant on an alphabetical list of obstetricians in England and Wales obtained from the RCOG (243) was surveyed by post and asked (a) "Would you agree to perform an elective CS on a woman with an uncomplicated singleton cephalic pregnancy at term for 'maternal request?"' and (b) if yes, in relation to this 'Has your practice changed over recent years?" Results: 155 questionnaires were returned (63% response rate-four unanswered, leaving 151 for analysis). One hundred and four (69%) consultants said they would agree to 'maternal request' for CS. Of the 'yes' respondents, 62 (60%) claimed their practice had changed recently. Conclusion: This survey demonstrates that a majority of obstetricians are now prepared to agree to maternal request for CS in the absence of obstetric indications. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved

The fetuses-at-risk approach: Clarification of semantic and conceptual misapprehension

<p>Abstract</p> <p>Background</p> <p>Although proponents of the fetuses-at-risk approach describe it as a causal model that resolves various conundrums, several areas of semantic and conceptual misapprehension remain. Differences in terminology include use of denominators such as 'ongoing pregnancies' and the need for an ad hoc 'correction factor' in order to calculate gestational age-specific rates. Further, there is conceptual disagreement regarding the proper candidates for neonatal death and related phenomena. Perhaps the most egregious misconception is the belief that rising rates of gestational age-specific perinatal mortality observed under the fetuses-at-risk model automatically imply the need for indiscriminate increases in iatrogenic preterm delivery.</p> <p>Discussion</p> <p>The term 'fetuses at risk' addresses the plurality of candidates for stillbirth in a multi-fetal pregnancy, while the use of standard terminology such as 'cumulative incidence' and 'incidence density' harmonizes the language of perinatal epidemiology with that used in the general epidemiologic literature. On the conceptual side, it is necessary to integrate clinical insights regarding latent periods into models of neonatal morbidity and mortality. The contention that the fetuses-at-risk approach implies the need for indiscriminate iatrogenic preterm delivery is a non-sequitur (just as rising age-specific cancer death rates do not imply the need for routine chemotherapy and radiation for all middle aged people). Finally, the traditional and fetuses-at-risk models are better viewed in terms of function as prognostic (non-causal) and causal models, respectively.</p> <p>Conclusion</p> <p>A careful examination of terms and concepts helps situate the traditional perinatal and the fetuses-at-risk approaches within the broader context of non-causal and causal models within general epidemiology.</p