Mortality following elective abdominal aortic aneurysm repair in women.

BACKGROUND: Previous studies have focused on patient-related risk factors to explain the higher mortality risk in women undergoing elective abdominal aortic aneurysm (AAA) repair. The aim of this study was to evaluate whether hospital-related factors influence outcomes following AAA repair in women. METHODS: Patients undergoing elective AAA repair in 61 hospitals in the Netherlands were identified from the Dutch Surgical Aneurysm Audit registry (2013-2018). A mixed-effects logistic regression analysis was conducted to assess the effect of sex on in-hospital and/or 30-day mortality. This analysis accounted for possible correlation of outcomes among patients who were treated in the same hospital, by adding a hospital-specific random effect to the statistical model. The analysis adjusted for patient-related risk factors and hospital volume of open surgical repair (OSR) and endovascular aneurysm repair (EVAR). RESULTS: Some 12 034 patients were included in the analysis. The mortality rate was higher in women than among men: 53 of 1780 (3.0 per cent) versus 152 of 10 254 (1.5 per cent) respectively. Female sex was significantly associated with mortality after correction for patient- and hospital-related factors (odds ratio 1.68, 95 per cent c.i. 1.20 to 2.37). OSR volume was associated with lower mortality (OR 0.91 (0.85 to 0.95) per 10-procedure increase) whereas no such relationship was identified with EVAR volume (OR 1.03 (1.01 to 1.05) per 10-procedure increase). CONCLUSION: Women are at higher risk of death after abdominal aortic aneurysm repair irrespective of patient- and hospital-related factors.

A mixture model for the analysis of data derived from record linkage.

Combining information from two data sources depends on finding records that belong to the same individual (matches). Sometimes, unique identifiers per individual are not available, and we have to rely on partially identifying variables that are registered in both data sources. A risk of relying on these variables is that some records from both datasets are wrongly linked to each other, which introduces bias in further regression analyses. In this paper, we propose a mixture model where we treat the indicator whether records belong to the same individual as missing. Each pair of records from both datasets contributes independently to a pairwise pseudo-likelihood, which we maximize with an expectation-maximization algorithm. Each part of the pseudo-likelihood is parameterized by the appropriate (parametric) density function. Moreover, some structures of the data allow for simplifying assumptions, which makes the pseudo-likelihood considerably easier to parameterize. Because the optimization requires a product over all combinations of records from both datasets, we suggest a procedure that summarizes information from highly unlikely matches. With simulations, we showed that the new approach produces accurate estimates in different linkage scenarios. Moreover, the estimator remained accurate in scenarios where previously proposed analysis approaches give biased results. We applied the method to estimation of the association between pregnancy duration of the first and second born children from the same mother from a register without mother identifier.

Time to conception and time to live birth in women with unexplained recurrent miscarriage.

STUDY QUESTION: What is the time to conception in a cohort of women with unexplained recurrent miscarriage (RM). SUMMARY ANSWER: Median time to conception in women diagnosed with unexplained RM was 21 weeks (interquartile range (IQR) 8-55 weeks), with a cumulative incidence of conception of 74% after 12 months of trying to conceive. WHAT IS KNOWN ALREADY: There is no effective treatment in couples with unexplained RM. Adequate counselling about their prognosis, for example time to conception and time to a live birth, is therefore very important. So far, there are no studies that give insight on these issues. STUDY DESIGN, SIZE, DURATION: A nested prospective cohort study was performed from February 2004 through July 2009 within a multicentre randomized placebo-controlled trial (ALIFE trial) on anticoagulant treatment in 364 women with unexplained RM. PARTICIPANTS/MATERIALS, SETTING, METHODS: A total of 251 women who were not pregnant at the time of diagnosis of unexplained RM were included in this study. Of these, 13% became pregnant with ART, and all other women conceived naturally. The primary outcome was time to conception in weeks, calculated from the moment of diagnosis until conception measured by a urinary HCG. Secondary outcome was time to a live birth in the subsequent pregnancy. The relative prognostic significance of female age, the number of preceding miscarriages, interventions within the trial and the presence or absence of a preceding late miscarriage, a previous live birth and factor V Leiden mutation, was evaluated by Cox regression for time to conception and by competing risk modelling for time to live birth, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: The cumulative incidence of conception was 56% after 6 months, 74% after 12 months and 86% after 24 months of which 65% resulted in a live birth. The median time to conception was 21 weeks (IQR 8-55 weeks). Of potential prognostic factors, the presence of the factor V Leiden mutation resulted in a significantly shorter median time to conception of 11 weeks for carriers versus 23 weeks for non-carriers (hazard ratio (HR) 1.94, 95% confidence interval (CI) 1.03-3.65). The cumulative incidence of a live birth of the subsequent pregnancy was 0% after 6 months, 23% after 12 months and 50% after 24 months. The median time to a live birth of the subsequent pregnancy was 102 weeks (IQR 82-115 weeks). The number of previous miscarriages was the only prognostic factor (HR 0.83, 95% CI 0.74-0.94) significantly associated with time to a live birth of the subsequent pregnancy. LIMITATIONS, REASONS FOR CAUTION: In our study only the subsequent pregnancy after diagnosing unexplained RM was included. A future collection of cumulative follow-up data of all the women included in this cohort may provide outcomes of all pregnancies following the diagnosis of unexplained RM. WIDER IMPLICATIONS OF THE FINDINGS: Time to conception in women diagnosed with unexplained RM appears to be comparable with time to conception in healthy fertile women, as reported in the literature. The interesting finding that women with Factor V Leiden mutation have a significant shorter time to conception may suggest a favourable embryo implantation process. Future research is needed to confirm these findings and unravel the biology of early implantation. STUDY FUNDING/COMPETING INTEREST(S): The RCT used for this nested cohort study was funded by a grant (945-27-003) from the Netherlands Organization for Health Research and Development and a grant from GlaxoSmithKline. Study drugs (aspirin and placebo) were packaged and donated by Meda Pharma. This analysis was supported by a VIDI innovative research grant from the Netherlands Organisation for Scientific Research (NWO) 016.126.364. There are no potential conflicts of interest to declare. TRIAL REGISTRATION NUMBER: This cohort study was nested in the randomized controlled trial; ALIFE study (Current Controlled Trials number, ISRCTN 58496168).

Using vaginal Group B Streptococcus colonisation in women with preterm premature rupture of membranes to guide the decision for immediate delivery: a secondary analysis of the PPROMEXIL trials.

OBJECTIVE: To investigate whether vaginal Group B Streptococcus (GBS) colonisation or other baseline characteristics of women with preterm premature rupture of membranes (PPROM) can help in identifying subgroups of women who would benefit from immediate delivery. DESIGN: Secondary analysis of the PPROMEXIL trials. SETTING: Sixty hospitals in the Netherlands. POPULATION: Women with PPROM between 34 and 37 weeks of gestation. METHODS: Random assignment of 723 women to immediate delivery or expectant management. MAIN OUTCOME MEASURES: Early onset neonatal sepsis. RESULTS: Vaginal GBS colonisation status was the only marker which was significantly associated with the benefit of immediate delivery (P for interaction: 0.04). GBS colonisation was observed in 14% of women. The risk of early onset neonatal sepsis in GBS-positive women was high (15.2%) when they were managed expectantly but this risk was reduced to 1.8% with immediate delivery. The early onset neonatal sepsis risk was much lower in neonates of GBS-negative women: 2.6% after expectant management and 2.9% with immediate delivery. We estimated that by inducing labour only in GBS-positive women, there would be a 10.4% increase in term delivery rate, while keeping neonatal sepsis and caesarean delivery rates comparable to a strategy of labour induction for all. CONCLUSIONS: Our post hoc findings suggest that women with PROM between 34 and 37 weeks might benefit from immediate delivery if they have GBS vaginal colonisation, while in GBS-negative women labour induction could be delayed until 37 weeks.

Methods for analyzing data from probabilistic linkage strategies based on partially identifying variables.

In record linkage studies, unique identifiers are often not available, and therefore, the linkage procedure depends on combinations of partially identifying variables with low discriminating power. As a consequence, wrongly linked covariate and outcome pairs will be created and bias further analysis of the linked data. In this article, we investigated two estimators that correct for linkage error in regression analysis. We extended the estimators developed by Lahiri and Larsen and also suggested a weighted least squares approach to deal with linkage error. We considered both linear and logistic regression problems and evaluated the performance of both methods with simulations. Our results show that all wrong covariate and outcome pairs need to be removed from the analysis in order to calculate unbiased regression coefficients in both approaches. This removal requires strong assumptions on the structure of the data. In addition, the bias significantly increases when the assumptions do not hold and wrongly linked records influence the coefficient estimation. Our simulations showed that both methods had similar performance in linear regression problems. With logistic regression problems, the weighted least squares method showed less bias. Because the specific structure of the data in record linkage problems often leads to different assumptions, it is necessary that the analyst has prior knowledge on the nature of the data. These assumptions are more easily introduced in the weighted least squares approach than in the Lahiri and Larsen estimator.

Recurrence risk of preterm birth in subsequent twin pregnancy after preterm singleton delivery.

OBJECTIVE: To determine the risk of preterm birth in a subsequent twin pregnancy after previous singleton preterm birth. DESIGN: Cohort study. SETTING: Nationwide study in the Netherlands. POPULATION: In all, 4071 nulliparous women who had a singleton delivery followed by a subsequent twin delivery between the years 1999 and 2007 were studied. METHODS: Outcome of subsequent twin pregnancy of women with a history of preterm singleton delivery was compared with pregnancy outcome of women with a history of term singleton delivery. First deliveries were subdivided into iatrogenic and spontaneous preterm deliveries. Furthermore analyses were performed by subgroups for gestational age at the time of singleton delivery. MAIN OUTCOME MEASURE: Spontaneous preterm birth (<37 weeks of gestation) in subsequent twin pregnancy. RESULTS: In the index singleton pregnancy, preterm birth occurred in 232 (5.7%) of 4071 women. The risk of subsequent twin preterm birth was significantly higher after previous singleton preterm delivery (56.9 versus 20.9%; odds ratio 5.0; 95% CI 3.8-6.6). Risk of subsequent twin preterm birth was dependent on the severity of previous singleton preterm birth and was highest after preceding spontaneous instead of iatrogenic singleton preterm delivery. CONCLUSION: Preterm birth of a singleton gestation is associated with an increased risk of spontaneous preterm birth in a subsequent twin pregnancy.

Comparison of growth between native and immigrant infants between 0-3 years from the Dutch ABCD cohort.

BACKGROUND: In the Netherlands separate reference charts have been developed for native and immigrant groups to deal with differences in growth patterns in later childhood. The use of these charts, however, is complicated by methodological issues; they do not represent all large Dutch immigrant groups in separate charts despite the differences that have been suggested and the evidence of ethnic disparities in growth dates back to 1997. AIM: Anthropometric measurements from a contemporary multi-ethnic cohort study were created to quantify differences in childhood growth by creating growth charts, separately for boys and girls between the ages of 0-3 years. SUBJECTS AND METHODS: The infants modelled in the charts had a mother born in the Netherlands (n = 3107), Suriname (n = 225), Turkey (n = 203) and Morocco (n = 336). Charts with and without correction for country of origin of the mother were created by using the LMST method. RESULTS: All models including the covariate country of origin of the mother fitted the data better (p < 0.0005), but the observed differences were small. CONCLUSION: Most remarkable differences were found in the BMI and weight measurements for age charts. Especially girls from mothers born in Turkey and Morocco had an increasingly heavier weight for their age than girls from mothers born in the Netherlands.