Infant mortality and subsequent risk of stillbirth: a retrospective cohort study

August, Euna M.; Hm, Salihu; Weldeselasse, Hanna; Biroscak, Brian J.; Mbah, AK; Alio, AP

doi:10.1111/j.1471-0528.2011.03137.x

Cited by 20 publications

(14 citation statements)

References 42 publications

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“…Although absolute risks were much higher than in western countries, the strength of association of a 3.2-fold recurrence risk observed in our data was consistent with associations observed in western countries [14-16]. Some studies have found slightly higher relative risks [9,17,18], and one study in Afro-American women estimated a four-fold recurrence risk [14].…”

Section: Discussionsupporting

confidence: 89%

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Recurrence of perinatal death in Northern Tanzania: a registry based cohort study

Mahande

Daltveit

Mmbaga

et al. 2013

BMC Pregnancy Childbirth

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BackgroundPerinatal mortality is known to be high in Sub-Saharan Africa. Some women may carry a particularly high risk which would be reflected in a high recurrence risk. We aim to estimate the recurrence risk of perinatal death using data from a hospital in Northern Tanzania.MethodsWe constructed a cohort study using data from the hospital based KCMC Medical Birth Registry. Women who delivered a singleton for the first time at the hospital between 2000 and 2008 were followed in the registry for subsequent deliveries up to 2010 and 3,909 women were identified with at least one more delivery within the follow-up period. Recurrence risk of perinatal death was estimated in multivariate models analysis while adjusting for confounders and accounting for correlation between births from the same mother.ResultsThe recurrence risk of perinatal death for women who had lost a previous baby was 9.1%. This amounted to a relative risk of 3.2 (95% CI: 2.2 - 4.7) compared to the much lower risk of 2.8% for women who had had a surviving baby. Recurrence contributed 21.2% (31/146) of perinatal deaths in subsequent pregnancies. Preeclampsia, placental abruption, placenta previa, induced labor, preterm delivery and low birth weight in a previous delivery with a surviving baby were also associated with increased perinatal mortality in the next pregnancy.ConclusionsSome women in Tanzanian who suffer a perinatal loss in one pregnancy are at a particularly high risk of also losing the baby of a subsequent pregnancy. Strategies of perinatal death prevention that target pregnant women who are particularly vulnerable or already have experienced a perinatal loss should be considered in future research.

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Section: Discussionsupporting

confidence: 89%

“…Some studies have found slightly higher relative risks [9,17,18], and one study in Afro-American women estimated a four-fold recurrence risk [14]. A 2-fold recurrence risk has been reported from Israel [11].…”

Section: Discussionmentioning

confidence: 99%

Recurrence of perinatal death in Northern Tanzania: a registry based cohort study

Mahande

Daltveit

Mmbaga

et al. 2013

BMC Pregnancy Childbirth

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“…This sharp increase became substantial when live births occurred more frequently. Furthermore, the increase is similar to previous studies that used the Kaplan–Meier method to right‐censor live births . Using the Kaplan–Meier approach, we showed that the risk of stillbirth in multiple pregnancies increased considerably after 35 weeks of gestation, with a five‐fold greater overall risk compared with the cumulative incidence method.…”

Section: Discussionsupporting

confidence: 87%

“…Furthermore, the increase is similar to previous studies that used the Kaplan-Meier method to right-censor live births. 1,2,13 Using the Kaplan-Meier approach, we showed that the risk of stillbirth in multiple pregnancies increased considerably after 35 weeks of gestation, with a five-fold greater overall risk compared with the cumulative incidence method. Similarly, the cumulative risk for singleton pregnancies increased sharply after 40 weeks, yielding a 2.5-fold greater overall risk.…”

Section: Discussionmentioning

confidence: 99%

Cumulative risk of stillbirth in the presence of competing events

Naimi

Auger

2016

BJOG

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Evidence suggests a sharp increase in stillbirth at the end of gestation. Between 35 and 38 weeks of gestation, cumulative risk of stillbirth in twin pregnancies increases by 60%, from 30 to 50 deliveries per 1000.1 A similar increase occurs after 37 weeks in singleton pregnancies.2 Although this evidence has implications for clinical practice, it is misleading. Increases in the cumulative risk of stillbirth at the end of gestation occur because researchers use the KaplanMeier method, which fails to account for live births as competing events.In studies of stillbirth, women can have three possible outcomes: stillbirth, live birth, or right-censoring. Rightcensoring occurs when a woman is no longer followed in a study (because of dropout or loss-to-follow-up), but is still at risk for the event. When a live birth occurs, the woman is no longer followed in a study because she is no longer at risk for the event. For this reason, live births (whether preterm or term) are competing events because they eliminate the possibility of stillbirth.3 Competing events are recognised in many areas of research. 4,5 In obstetric studies of stillbirth, competing events are arguably more important because of the natural increase in live births near term. However, to our knowledge, only one letter in the obstetrics literature has raised concern over inappropriate treatment of competing events. 6 The purpose of this commentary is to clarify why the Kaplan-Meier approach should not be used when competing events are present. To illustrate, we calculate the incorrect risk of stillbirth in a cohort of roughly two million pregnancies in Quebec, Canada. We describe the degree of error, explain why the error occurs, and show how to obtain correct estimates of cumulative risk when competing events are present. We conclude with a mention of the broader debate on how best to define the cumulative risk of stillbirth. Kaplan-Meier versus cumulative incidenceThere are several ways to compute cumulative risk. The Kaplan-Meier method 7 is the most common. The KaplanMeier method correctly estimates cumulative risk when there is right-censoring. 8 Women who are right-censored are still at risk of stillbirth even though they are lost to follow up, but the exact timing and outcome of pregnancy is not known.The Kaplan-Meier approach is incorrect when competing events are present. [3][4][5][6][8][9][10][11] To censor live births, the Kaplan-Meier method 'redistributes' the potential stillbirth risk for a given pregnancy to subsequent stillbirths from other pregnancies. In doing so, the Kaplan-Meier method requires the assumption that women with live births are still at risk of stillbirth, which evidently is impossible. As a result, when there is no loss to follow up but competing events are present, the Kaplan-Meier stillbirth risk estimated after all pregnancies have delivered is not identical to the overall (empirical) risk of stillbirth in the cohort.An alternative approach is known as the cumulative incidence method, which can estimate cumulative st...

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“…Over the same period, there have been changes in stillbirth risk factors. Births to women of higher‐risk groups increased including older mothers, lower socioeconomic status, obese, diabetic, women with previous stillbirths or preterm births, and infants conceived using ART, commonly reported risk factors for stillbirth 10,11,26–28 . Conversely, there were contemporaneous decreases in other high‐risk groups including teenage mothers, smokers, infection, pregnancy hypertension and some chronic conditions, which are also known risk factors for stillbirth 11,28,29,30 …”

Section: Discussionmentioning

confidence: 99%

Trends and recurrence of stillbirths in NSW

Patterson

Ford

Morris

et al. 2014

Australian and New Zealand Journal of Public Health

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Objective: To examine the trend in stillbirth rates adjusted for the trends in the maternal risk profile, and to use local data to estimate the stillbirth recurrence risk.\ud Methods: Linked hospital, birth and perinatal death review data were used to identify risk factors and stillbirths among women giving birth to singletons in NSW between 2001 and 2009. Logistic regression models were developed to predict stillbirth rates based on the changes in the maternal population.\ud Results: Between 2001 and 2009 there were 3449 stillbirths (4.4 per 1000 births), with no significant change in rate overall (p=0.6) or across older gestational age categories (26-33 weeks p=0.67, >=34 weeks p=0.36), and a slight increase at <26 weeks (p=0.01). However, when changes in the maternal population were taken into account, there was a significant increase in stillbirths at <26 weeks (p<0.001). Women with a stillbirth in a first pregnancy were at increased risk of stillbirth in their second pregnancy (4.3 95% CI (2.4,7.7)).\ud Conclusion: There has been no decline in the stillbirth rate in NSW in recent years, which at late gestations may be accounted for by changes in the maternal population. At early gestations, there has been an increase in stillbirths where a decrease in rate may be expected based on the maternal population.\ud Implications: Further focus on addressing risk factors for stillbirths is needed to ensure continued progress is made in reducing stillbirths.Stillbirth Foundation Australia. ARC Future Fellowship (#120100069). NHMRC Senior Research Fellowship (#1021025).Healthy Start To Life; Kolling Institute of Medical Researc

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Infant mortality and subsequent risk of stillbirth: a retrospective cohort study

Cited by 20 publications

References 42 publications

Recurrence of perinatal death in Northern Tanzania: a registry based cohort study

Recurrence of perinatal death in Northern Tanzania: a registry based cohort study

Cumulative risk of stillbirth in the presence of competing events

Trends and recurrence of stillbirths in NSW

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