Parity specific perinatal mortality. A longitudinal study based on sibships

Risk factors for perinatal mortality in Murmansk County, Russia: a registry-based study

Background: Factors contributing to perinatal mortality (PM) in Northwest Russia remain unclear. This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birth Registry.

Objective: This study investigated possible associations between selected maternal and fetal characteristics and PM based on data from the population-based Murmansk County Birth Registry.

Methods: The study population consisted of all live- and stillbirths registered in the Murmansk County Birth Registry during 2006–2011 (n = 52,806). We excluded multiple births, births prior to 22 and after 45 completed weeks of gestation, infants with congenital malformations, and births with missing information regarding gestational age (a total of n = 3,666) and/or the studied characteristics (n = 2,356). Possible associations between maternal socio-demographic and lifestyle characteristics, maternal pre-pregnancy characteristics, pregnancy characteristics, and PM were studied by multivariable logistic regression. Crude and adjusted odds ratios with 95% confidence intervals were calculated.

Results: Of the 49,140 births eligible for prevalence analysis, 338 were identified as perinatal deaths (6.9 per 1,000 births). After adjustment for other factors, maternal low education level, prior preterm delivery, spontaneous or induced abortions, antepartum hemorrhage, antenatally detected or suspected fetal growth retardation, and alcohol abuse during pregnancy all significantly increased the risk of PM. We observed a higher risk of PM in unmarried women, as well as overweight or obese mothers. Maternal underweight reduced the risk of PM.

Conclusions: Our results suggest that both social and medical factors are important correlates of perinatal mortality in Northwest Russia.

Long-term mortality in mothers with perinatal losses and risk modification by surviving children and attained education: a population-based cohort study

OBJECTIVE

To assess the association between perinatal losses and mother's long-term mortality and modification by surviving children and attained education.

DESIGN

A population-based cohort study.

SETTING

Norwegian national registries.

PARTICIPANTS

We followed 652 320 mothers with a first delivery from 1967 and completed reproduction before 2003, until 2010 or death. We excluded mothers with plural pregnancies, without information on education (0.3%) and women born outside Norway.

MAIN OUTCOME MEASURES

Main outcome measures were age-specific (40-69 years) cardiovascular and non-cardiovascular mortality. We calculated mortality in mothers with perinatal losses, compared with mothers without, and in mothers with one loss by number of surviving children in strata of mothers' attained education (<11 years (low), ≥11 years (high)).

RESULTS

Mothers with perinatal losses had increased crude mortality compared with mothers without; total: HR 1.3 (95% CI 1.3 to 1.4), cardiovascular: HR 1.8 (1.5 to 2.1), non-cardiovascular: HR 1.3 (1.2 to 1.4). Childless mothers with one perinatal loss had increased mortality compared with mothers with one child and no loss; cardiovascular: low education HR 2.7 (1.7 to 4.3), high education HR 0.91 (0.13 to 6.5); non-cardiovascular: low education HR 1.6 (1.3 to 2.2), high education HR 1.8 (1.1 to 2.9). Mothers with one perinatal loss, surviving children and high education had no increased mortality, whereas corresponding mothers with low education had increased mortality; cardiovascular: two surviving children HR 1.7 (1.2 to 2.4), three or more surviving children HR 1.6 (1.1 to 2.4); non-cardiovascular: one surviving child HR 1.2 (1.0 to 1.5), two surviving children HR 1.2 (1.1 to 1.4).

CONCLUSIONS

Irrespective of education, we find excess mortality in childless mothers with a perinatal loss. Increased mortality in mothers with one perinatal loss and surviving children was limited to mothers with low education.

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

Background

Perinatal 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.

Methods

We 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.

Results

The 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.

Conclusions

Some 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.

Recorded pregnancy histories of the mothers of singletons and the mothers of twins: a longitudinal comparison

A population-based record linkage case cohort of 239,995 births, to 119,214 women, born in Western Australia from 1980 to 2001 inclusive, was used to measure the recording of selected indicators of maternal health (current and prior) during pregnancy. We compared records of women with singleton pregnancies with that in twin pregnancies Mothers of first- and second-born singletons (n = 117,647) were compared with women with a first-born singleton followed by twins (n = 1,567). Binary indicators were used to calculate population prevalence of medical conditions, pregnancy complications and birth outcomes. Infant outcomes included stillbirth, low birthweight, preterm birth and birth defects. Women with twins were significantly older and taller, with similar rates of medical conditions and pregnancy complications during first singleton pregnancies compared with women with two consecutive singletons. However, during their second pregnancy, women with twins had significantly higher rates of essential hypertension, pre-eclampsia, threatened abortion, premature rupture of the membranes and ante partum hemorrhage with abruption than women with singletons. For both groups, maternal conditions in the first pregnancy were underreported in the second pregnancy, including diabetes, epilepsy, asthma, chronic renal dysfunction and essential hypertension. At the second birth, twins were 3 times more likely to be stillborn, 17 times more likely to be low birthweight and 4 times more likely to be delivered preterm compared with singletons. This research demonstrates the importance for epidemiologists and others, of having access to a complete maternal medical history for analyses of risks associated with maternal, infant and childhood morbidity.

Secular trends of sudden infant death syndrome in Norway 1967-1988: application of a method of case identification to Norwegian registry data

In Norway, towards the end of the 1980s, sudden infant death syndrome (SIDS) was the most frequent cause of infant death. Both SIDS and the total post-perinatal mortality rates had increased. This paper presents a procedure for identifying SIDS from death certificates. Supplemented with additional information, a database was established to evaluate secular trends of SIDS and for further analytical research. The Medical Birth Registry of Norway comprises 1.3 million births from 1967 to 1988. Of these, 5447 infants died in the post-perinatal period. The cause of death was reviewed by an expert panel and 1984 cases of SIDS were retrieved. Low maternal age, higher birth order, male gender, and lower birth-weight were confirmed as risk factors for SIDS. In 1988, the rate for SIDS and for total post-perinatal deaths reached 2.69 and 5.02 per 1000 infants at risk. The incidence of SIDS increased 2.2 times from the period 1967-1971 to the period 1987-1988. Adjusted for maternal age, birth order, and birthweight, the odds ratio was 3.1. The increase is due to factors not yet accounted for. Adjusted mortality rates for the other post-perinatal deaths were not different from the crude rates.

A comparison of recurrent and isolated small-for-gestational-age term births

In this study, based on total Western Australian singleton Caucasian births, women who had repeatedly given birth to small-for-gestational-age (SGA) term infants ('repeater' mothers) were compared with multiparous women who had had only one such infant ('non-repeater' mothers). Women with any preterm births were excluded. The study population comprised 678 repeater and 986 non-repeater mothers. Multiple logistic regression analysis indicated that weight loss or static weight in the third trimester of pregnancy, paternal smoking, low maternal birthweight, short maternal height and unknown family disease history were independent risk factors for repeater status compared with non-repeaters. The risk associated with paternal smoking was confined to mothers who were non-smokers themselves. There may have been a direct association between paternal smoking and recurrent fetal growth retardation or paternal smoking may have acted as a 'marker' for certain behavioural, environmental, social and economic factors which were not measured. Neonatal outcome was worse for the SGA infants of non-repeater mothers than for those of repeater mothers, although the latter were significantly more likely to weight less than 2500 grams.

Classification of small-for-gestational age births: weight-by-gestation standards of second birth conditional on the size of the first

Percentiles of weight-by-gestational age were constructed for first and second births, based on linked sibship-data from the Medical Birth Registry of Norway. Standards were made for weight-by-gestational age of second births conditional on whether the first birth was small-for-gestational age (SGA) or large-for-gestational age (LGA). These standards were compared with the conventional, cross-sectional standard of all second births. The relevance of the conditional standards was assessed on the basis of perinatal mortality, using logistic regression analyses. When applying cross-sectional standards of second births, more than 30% of the births following a SGA first birth were classified as SGA, compared with only 1.7% following an LGA first births. The overall risk for a perinatal loss in second births following a SGA first birth was twice that among second births following a LGA first birth. When second births were themselves categorised as SGA or non-SGA using the cross-sectional standards, the mortality among the SGA second births was such that the risk was 4 to 5 times higher following LGA first births compared with SGA first births. When conditional standards were applied to define SGA among second births, the risk relation between the subgroups (defined by classification of first birth) corresponded to the observed overall risk pattern. An unconditional SGA classification conceals important differences between clinically distinct subgroups.