An assessment of the effects of maternal age and parity in different components of perinatal mortality

Perinatal mortality has several components which may have distinct epidemiologic features. In an investigation of the total singleton birth population of New York City in 1976-1978 (n = 320,726), the authors divided perinatal mortality into four components: late fetal deaths that occurred before labor (late antepartum fetal deaths), fetal deaths during labor (intrapartum fetal deaths), neonatal deaths, and perinatal deaths attributed to congenital anomalies, and they assessed the relation of each of these to maternal age and parity, controlling for relevant confounding factors. In analyses which controlled for prior fetal loss, type of service (public vs. private), race, marital status, and mother's educational attainment in a multiple logistic regression model, the authors found that: 1) increasing maternal age was strongly associated with antepartum fetal deaths but not with intrapartum fetal deaths, while older maternal age was also associated with perinatal deaths attributed to congenital anomalies; 2) high parity bore a strong relationship to intrapartum fetal deaths, but none to antepartum fetal deaths, neonatal deaths, or congenital anomaly deaths; and 3) for neonatal death, there was a statistically significant (p less than 0.001) interaction between parity and age such that mothers over 34 years old having their first birth were at especially high risk.     

Demographic survey of the level and determinants of perinatal mortality in Karachi, Pakistan

Summary. .A demographic survey was used to estimate the level and determinants of perinatal mortality in eight lower socio-economic squatter settlements of Karachi, Pakistan. The perinatal mortality rate was 54.1 per 1000 births, with a stillbirth to early neonatal mortality ratio of 1:1. About 65% of neonatal deaths occurred in the early neonatal period, and early neonatal mortality contributed 32% of all infant deaths. Risk factor assessment was conducted on 375 perinatal deaths and 6070 current survivors. Poorer socio-economic status variables such as maternal and paternal illiteracy, maternal work outside the home and fewer household assets were significantly associated with perinatal mortality as were biological factors of higher parental age, short birth intervals and poor obstetric history. Multivariable logistic analysis indicated that some socioeconomic factors retained their significance after adjusting for the more proximate biological factors. Population attributable risk estimates suggest that public health measures for screening of high-risk women and use of family planning to space births will not improve perinatal mortality substantially without improvement of socio-economic conditions, particularly maternal education. The results of this study indicate that an evaluation of perinatal mortality can be conducted using pregnancy histories derived from demographic surveys.     

Perinatal mortality in rural Malawi.

Reported are the results of a study to assess the prevalence and risk factors for perinatal death among pregnant women in Malawi over the period 1987-90. There were 264 perinatal deaths among the 3866 women with singleton pregnancies (perinatal mortality rate, 68.3 per 1000 births). Among the risk factors for perinatal mortality were the following: reactive syphilis serology, nulliparity, a late fetal or neonatal death in the most recent previous birth, maternal height < 150 cm, home delivery, and low socioeconomic status. Although unexplained perinatal deaths will continue to occur, perinatal mortality can be reduced if its causes and risk factors in a community are given priority in antenatal and intrapartum care programmes. The following interventions could potentially reduce the perinatal mortality in the study population: screening and treating women with reactive syphilis serology; and management from early labour, by competent personnel in a health facility, of nulliparous women and multiparous women who are short or have a history of a perinatal death.     

Risk factors for perinatal deaths in rural Bangladesh

Perinatal mortality refers to stillbirths and deaths which occur during the first week of life. 7 million such deaths occur annually worldwide, almost all of which are in developing countries. Rates as high as 75-100 deaths/1000 births have been documented in developing countries. The 3 leading causes of perinatal mortality are complications of pre-term birth, birth asphyxia and birth trauma, and bacterial infections. The other causes of perinatal mortality are largely unknown due to difficulties in documenting stillbirths in developing countries. In many developing country societies, it is culturally unacceptable to acknowledge a birth until it has survived its first week of life. This study identified and quantified the risk factors for perinatal deaths in a rural community in Manikganj district, Bangladesh. Cases were mothers whose infants died in the perinatal period, while comparison mothers were those whose infants survived the perinatal period. Of the 186 infant deaths recorded, 130 (69.9%) were in the perinatal period, and included 53 stillbirths. The perinatal death rate was 64.5/1000 births. Logistic regression confirmed that maternal age, parity, and mal-presentation were significantly associated with perinatal deaths. Mal-presentation was independently associated with a increased risk of perinatal death.     

A Secondary Analysis of Race/Ethnicity and other Maternal Factors Affecting Adverse Birth Outcomes in San Bernardino County

Objectives Though it is the largest county in the lower United States, minimal attention has been given to the elevated rates of poor perinatal outcomes and infant mortality in San Bernardino County. This study sought to analyze adverse birth outcomes such as low birth weight, and infant mortality as an outcome of specific proxy maternal sociodemographic factors. Methods Data from the California Department of Health Services Office of Vital Statistics birth cohort of mothers delivering between 1999 and 2001 (N = 1,590,876 participants) were analyzed. Of those, 5.5% (n = 86,736) were births in San Bernardino County. Low birth weight, very low birth weight, death in infants less than one year of age, and other maternal sociodemographic factors were explored. All events of low birth weight and deaths among infants less than one year of age were used as significant variables in statistical models. Results Black mothers experienced more than twice the rate of very low birth weight (3.89) than their White counterparts (1.39). The most significant contributors to adverse birth outcomes among Black women were length of gestation and maternal education, whereas the most significant predictor of infant mortality was birth weight. Conclusions This study demonstrates that traditional risk factors such as length of gestation and maternal age only partially explain adverse birth outcomes. These findings highlight the need to advocate for the systematic collection of data on maternal education and length gestation and for the promotion of public health initiatives that address these inequities in our most vulnerable of populations.     

Maternal predictors of perinatal mortality: the role of birthweight.

BACKGROUND: Many maternal characteristics increase the risk for perinatal death. To locate potential sites for intervention, it is important to identify these risk factors and examine how much of the excess mortality is explained by infants' low birthweight. METHODS: Data on all newborns in Finland born between 1991 and 1993 (N = 199,291, of which 1461 were perinatal deaths) were obtained from the Medical Birth Register. Logistic regression analysis was used to adjust for background variables, both including and excluding infants' birthweight. The percentage reduction in odds ratios after adjustment for infants' birthweight was used to estimate the contribution of infants' low birthweight to the excess mortality. RESULTS: After adjusting confounding factors, increased risk for perinatal death was found for eight maternal characteristics. In the following the increased risk is given as odds ratios and the proportions of the excess mortality explained by infants' low birthweight are in parentheses: in-vitro fertilization 4.12 (> 100%); earlier stillbirth 3.43 (87%); higher maternal age, from 1.21 to 3.08 (38-99%); maternal diabetes 2.87 (50%); lower socioeconomic status, from 1.30 to 1.70 (27-44%); smoking during pregnancy 1.45 (> 100%); single mother 1.44 (50%); first birth 1.36 (75%). CONCLUSIONS: Excess mortality due to maternal risk factors occurred mainly through their tendency to cause low birthweight. However, the excess mortality associated with low socioeconomic status, single motherhood, and diabetes was mediated by other mechanisms in addition to low birthweight.     

Ethnic differences in perinatal mortality--a challenge.

The perinatal mortality rates of mothers who delivered at St. Thomas's Hospital from 1969 to 1976 have been examined. The rate in the West Indian population was significant higher than in the United Kingdom white population. The increased West Indian mortality was confined to infants with a birth weight of more than 2.0 kg and a gestational age of more than 37 weeks. The relative risk of perinatal death for West Indian mothers compared with UK white mothers was 1.4 at birth weights of 2.5 kg to 2.9 kg, rising to 4.3 at 4.0 + kg. West Indian perinatal mortality in term babies of normal birth weight was higher in all maternal age and parity groups except parity 3, but the difference was greatest in women aged 30 or over. The African perinatal mortality rate was not significantly greater than the UK white rate although it followed the West Indian trends. Pre-eclampsia and forceps delivery were associated with a greatly increased perinatal mortality in West Indian babies. The excess West Indian mortality could not be explained completely by differences in the proportions of stillbirths and early neonatal deaths nor by the distribution of births by parity, maternal age, or social class. Possible explanations for the differences in mortality are discussed.     

Maternal education in relation to early and late child health outcomes: findings from a Brazilian cohort study.

In a population-based cohort of approximately 6000 Brazilian children, the associations between maternal education and a number of child health outcomes were studied while controlling for potentially confounding variables such as family income and education of the husband. In the crude analyses, maternal education was associated with perinatal and infant mortality, hospital admissions in the first 20 months of life and the three nutritional indicators (length-for-age, weight-for-age and weight-for-length) at mean age 20 months. After adjustment for confounding, the apparent associations with outcomes in early infancy--birthweight and perinatal mortality--were no longer present, while that with infant mortality persisted despite being reduced. Strong associations remained with later outcomes including hospital admissions, length-for-age and weight-for-age at mean age 20 months. Among infants born to women with little or no schooling, deaths due to diarrhoea, pneumonia and other infectious diseases were particularly common. These findings support the hypothesis that maternal education has an effect on child health which is partly independent from that of other socioeconomic factors; they also suggest that maternal care is more important than the biological characteristics of the mothers since stronger effects were observed for the late (postneonatal mortality, hospital admissions and nutritional status) than for the early (birthweight, perinatal mortality) outcomes.     

Trends in perinatal characteristics in South Australia, 1981 to 1994, by place of residence of mother

Abstract: We investigated differentials and time trends in perinatal mortality and perinatal risk factors by geographic area of residence in South Australia during 1981–1994, to assess whether sociodemographic inequalities had lessened. The areas analysed were Adelaide and the country region of South Australia, with Adelaide being divided by socioeconomic status into two areas. Subjects were 267 116 singleton births of at least 400 g birthweight (or at least 20 weeks' gestation) notified to the state's perinatal data collection. Year of birth, residential area, and interactions between year of birth and residential area were analysed as predictors of perinatal risk factors and deaths. There was a statistically significant decline in the perinatal death rate in all residential areas (mainly because of a decrease in neonatal deaths), which did not vary significantly by area. The frequency of low birthweight (< 2500 g) increased in the country areas and in the lower socioeconomic areas of Adelaide, but not in the higher socioeconomic areas. Although premature births increased in all areas, the increase was less pronounced for the higher socioeconomic areas of Adelaide. By comparison, although all areas showed an increase in the proportions of mothers aged 35 years or over, the increase was larger for the higher socioeconomic areas. Australia has a national policy of reducing social inequalities in health status. Perinatal mortality rates declined in Adelaide and country residential areas from 1981 to 1994. This trend is favourable, but from the relativities of these rates by residential area, there is not compelling evidence of a reduction in inequalities.     

Antenatal booking and perinatal mortality in Scotland 1972-1982

Data from Scottish maternity hospital discharge returns (SMR2) were analysed to determine the relationship between gestational age at antenatal booking and perinatal mortality during 1972-82, controlling for maternal age, parity, socioeconomic and marital status. Maternal youth, multiparity and unmarried status were independently associated with both a high perinatal mortality and a low proportion of maternities booked before 17 weeks gestation. However, among primiparae and mothers aged 30 years or more relatively high perinatal mortality rates were associated with high proportions booking early for antenatal care. Socioeconomic status amongst married women, independent of age and parity, influenced perinatal mortality but had little effect on booking behaviour. Between 1972-75 and 1980-82, there was a general increase in the proportion of maternities booked before 17 weeks gestation, but no significant difference was found between the standardized perinatal mortality rates for pregnancies booked before and after 17 weeks gestation. More detailed analysis for different gestational ages at booking during 1980-82 revealed no trend of increasing risk with later booking. Despite technological advances, antenatal care during the first half of pregnancy is unlikely to have made a substantial contribution to the fall in perinatal mortality over this period.     

Perinatal mortality in a first generation immigrant population and its relation to unemployment in The Netherlands.

STUDY OBJECTIVE--To consider the association between biological and social risk factors and perinatal mortality in an ethnically mixed population in Amsterdam, The Netherlands. DESIGN--This was a matched case-control study. Cases included all registered stillborn infants and all registered liveborn infants who died within seven days of birth. Controls were selected from infants remaining alive. Each case was matched with two controls by date of registration. SETTING--Civil registry of births and deaths, Amsterdam, The Netherlands, 1975-80. PATIENTS--All 666 babies who died in the perinatal period and 1332 controls selected from the liveborn survivors. OUTCOME--Perinatal mortality. MAIN RESULTS--Perinatal mortality was independently associated with the father's and mother's employment status, maternal age, parity, and infant sex, but not with the father's or mother's country of birth. CONCLUSIONS--Employment status and not country of birth should be the main focus in studies of perinatal mortality in this population of mixed ethnicity. Future studies on selected behavioural, socio-economic, and cultural factors are needed to provide a better understanding of the causes of increased perinatal mortality among families in which the parents are unemployed.     

Parity specific perinatal mortality. A longitudinal study based on sibships

Perinatal mortality in sibships has been examined using the Medical Birth Registry of Norway. Using linear logistic regression, parity specific perinatal mortality in the period 1967-1981 has been analysed, controlling simultaneously for maternal age, year of birth and survival of earlier births. The risk of a perinatal loss was increased by a factor of up to 6.0 following one earlier perinatal loss, and with three earlier losses the increase was 17.0. The general reduction in mortality between the different five year periods varied according to parity and maternal age. No secular reduction in risk, however, was demonstrated in sibships where the first birth died perinatally; for some subgroups of women the risk actually increased between the first and the second five year period. The effect of maternal age changed with parity, being strong in the first birth order, but of no effect either for the third or the fourth birth orders once the perinatal survival of earlier births was controlled for. This study shows the need to take heterogeneity of risk between women into account in studies of perinatal loss; the overall improvement in perinatal mortality does not apply to every woman. As care improves, perinatal losses become less and less random, demonstrated by increased risks of recurrence.     

The determinants of the high Dutch perinatal mortality in a complete regional cohort, 1990-1994

OBJECTIVE: Analysis of the effects of population-based determinants (maternal age, parity, multiple pregnancy and ethnicity) and of professional and organisational factors (conservative management in case of early preterm birth, the policy on prenatal screening and the Dutch obstetric-care system in general) on perinatal mortality. DESIGN: Population-based prospective cohort study. METHOD: In a regional cohort (Zaanstreek) of 8031 pregnancies in the period 1990-1994 data were prospectively collected in an electronic database by deliverers of primary and secondary care. Analysis focussed on the effect on perinatal mortality of maternal age, parity, multiple pregnancy, ethnicity and professional and organisational factors (the policy in case of early preterm birth, the policy on prenatal screening and the Dutch obstetric-care system in general). Perinatal mortality was defined as mortality from a gestational age of 22 weeks until 28 days post partum. RESULTS: The perinatal mortality in the Zaanstreek was 12.6/1000. Increasing the gestational age to 28 weeks decreased the perinatal mortality by 29%. The perinatal mortality in this cohort was significantly affected by parity, multiple pregnancy and maternal age (relative risk: 2.8), but not by ethnicity if corrected for the previous factors. Conservative management in case of early preterm birth and a restrictive screening policy for lethal birth defects were associated with an increase in perinatal mortality. In 31 of 92 singleton pregnancies followed by perinatal mortality, a relationship to substandard care was established. In 7 cases this relationship was probable and in 1 case the midwife was responsible. CONCLUSION: Given the magnitude of their effects, both independently and via interaction, stratification for maternal age, parity, multiple pregnancy and ethnicity must precede any interpretation and comparison of perinatal mortality rates. Although clinical policy played a modest role, a negative role of the organisation of obstetric care was unlikely in this cohort. A definitive judgement as to the quality of perinatal care would require extension of the evaluation to at least the entire first year of life in connection with the morbidity. The most favourable effects can be expected from stimulatory measures directed at lowering the age at first pregnancy.     

Perinatal mortality associated factors in a general hospital of Chiapas, Mexico

OBJECTIVE: To identify socioeconomic, gynecological-obstetric and fetal factors associated with perinatal mortality. METHODS: A matched case-control study was carried out. Cases were newborns (born live or dead) that were born and died between 28 weeks gestation and 7 days of life. Controls were live newborns between 28 weeks gestation and 7 days of life. A total of 99 cases and 197 controls were studied. Data were obtained from the corresponding medical charts. Statistical analysis was performed using Stata 6.0 software. RESULTS: Mean maternal age was 24.82 years and mean newborn age was 37.78 weeks gestation with an average birth weight of 2,760 grams. Factors associated with perinatal mortality were: father's occupation as a farmer (adjusted odds ratio (OR)=3.31; 95% CI=1.26-8.66); high obstetric risk index (adjusted OR=10.57; 95% CI=2.82-39.66), cesarean birth (adjusted OR=2.75; 95% CI=1.37-5.51), five or more prenatal visits (adjusted OR=4.43; 95% CI=1.86-10.54) and preterm fetal maturity indices (PEG, APG, GEG) (adjusted OR=9.20; 95% CI=4.39-19.25). CONCLUSIONS: The risk factors associated with perinatal mortality found in the study are consistent with the findings reported in the international literature. These results show that prevention and control measures should be implemented to identify at risk pregnant women in order to lower perinatal mortality.     

Changing risks of stillbirth and neonatal mortality associated with maternal age in Western Australia 1984-2003

There has been a trend over the past two decades in some Western countries for women to delay childbearing, a factor associated with an increased risk of perinatal mortality (stillbirth and neonatal death). While the rates of stillbirth and neonatal mortality have improved in some countries, it has not been established whether maternal age remains a risk factor for perinatal mortality in Australia. The Western Australian Maternal and Child Health Research Database (MCHRDB) was used to examine the effect of maternal age on perinatal death in the periods 1984-93 and 1994-2003 after adjustment for parity and sociodemographic factors. Stillbirths and neonatal deaths were analysed separately. The crude rate of stillbirth has shown little change over the 20 years examined remaining at around 7.5 per 1000 total births, while the rate of neonatal death has decreased steadily from 5.4 per 1000 livebirths in 1984 to 2.0 in 2003. Older maternal age remains a risk factor for stillbirth but the relative risk has declined. After adjustment for parity and sociodemographic factors the relative risk of stillbirth for a woman aged over 40 years (compared with a woman aged 25-29 years) decreased from 2.6 in the period 1984-93, to 1.9 in the period 1994-2003. The increased risk of stillbirth associated with teenage mothers was fully explained by sociodemographic factors in both time periods. No increased risk of neonatal death was evident in the recent period 1994-2003 for teenage or older mothers after adjustment for parity and sociodemographic factors. In spite of some improvements over the past 20 years, women 30 years of age and older continue to be at increased risk of stillbirth. The risk of neonatal death is no longer associated with increased maternal age; however, the small number of cases in the older maternal age groups may be a result of the increased prevalence of antenatal screening and terminations for birth defects.     

The importance of preterm births for peri- and neonatal mortality in rural Malawi

Peri- and neonatal mortality remain high in developing countries, especially in sub-Saharan Africa. In the present study, we quantified and identified the most important predictors of early mortality in rural Malawi. Data were obtained from a community-based cohort of 795 pregnant women and their 813 fetuses, followed prospectively from mid-pregnancy. In this group, peri- and neonatal mortality rates were 65.3 deaths per 1000 births and 37.0 deaths per 1000 live births respectively. When controlled for month of birth, maternal age and selected socio-economic variables, preterm birth was the strongest independent predictor of both peri- and neonatal mortality (adjusted odds ratios 9.6 for perinatal and 11.0 for neonatal mortality; 95% confidence intervals: [4.4, 21.0] and [3.7, 32.7] respectively). Weaker risk factors for mortality included a maternal history of stillbirth and abnormal delivery. Preterm delivery was associated with primiparity and peripheral malaria parasitaemia of the mother, and it accounted for 65% of the population-attributable risk for perinatal and 68% of the neonatal mortality. Successful intervention programmes to reduce peri- and neonatal mortality in Malawi have to include strategies to predict and prevent prematurity.     

The association of maternal smoking with age and cause of infant death

Linked birth certificate and infant death certificate data from Missouri for 1979-1983 were used to explore the association of maternal smoking with age and cause of infant death. The data included 305,730 singleton white livebirths, of which 2,720 resulted in infant deaths. Using multiple logistic regression to control for the confounding effects of maternal age, parity, marital status, and education, the authors found that smoking was associated with both neonatal and post-neonatal mortality and with each cause of death except congenital anomalies. The adjusted odds ratio for smoking was higher for postneonatal deaths than neonatal deaths and was particularly high for two causes: respiratory disease (odds ratio = 3.4) and sudden infant death syndrome (odds ratio = 1.9). A moderate odds ratio (about 1.4) was found for causes attributed to the International Classification of Diseases, 9th Revision Perinatal Conditions Chapter. Although the associations for neonatal deaths and perinatal conditions were partially attributable to the effect of maternal smoking in lowering birth weight, virtually none of the excess respiratory mortality and sudden infant death syndrome mortality among the offspring of smokers was attributable to birth weight differences between the infants of smokers and nonsmokers. This suggests that respiratory deaths and sudden infant death syndrome deaths may be related to the effect of passive exposure of the infant to smoke after birth.     

Ethnicity, nationality and health care accessibility in Kuwait: a study of hospital emergency room users

In mid-1994, non-Kuwaiti expatriates constituted 61.7% of the total population of Kuwait (1.75 million). Despite this numerical majority, non-Kuwaitis exist as a social minority. Non-Kuwaitis may be grouped into three broad categories along ethnic/nationality lines into Bidoon (without nationality), Arabs, and Asians. The objective of this paper was to compare the relative accessibility of the various groups to health care services in Kuwait. The study is based on data collected as part of a survey of 2184 Emergency Room (ER) users in January-February 1993. All patients attending the hospital ERs between 7:30 am and 9:00 pm were interviewed about their reasons for coming to the ER instead of going to the primary health care (PHC) centres, as required. The major reason given was low accessibility of the PHCs. Compared to Kuwaiti nationals, 92% of whom were registered at the PHC centres, only 62% of the Arabs and 39% of the Asians were registered. Multiple logistic regression of the factors in registration indicated that nationality was the most important reason for lack of registration, with Asians only about one-quarter as likely to be registered as Kuwaitis. Also, people who had been in Kuwait for shorter durations (< 5 years) were less likely to be registered than the Kuwaiti nationals or expatriates who had been here for 10 years or longer. In the absence of registration at the PHC centre, the civil identification card (ID) may be used as a valid means to enter the health system. Among the Arabs and Asians, 22% and 29% did not have a civil ID card. Thus, for many expatriates, the hospital ER, which does not provide the necessary follow-up care is often the only source of health care available.     

Exploring the maternal and infant continuum – ethnic disparities in infant hospital admissions for respiratory disease

Objective: To investigate maternal and birth‐related risk factors associated with infant respiratory hospitalisations in New Zealand. Methods: A Kaupapa Māori‐framed retrospective cohort analysis of public hospital maternal data linked to infant data (54,980 births 1995–2009). Primary outcome was rate of hospitalisation for respiratory disease in the first year of life. Risk variables examined included socioeconomic status (SES), age, smoking, parity, gestation, time to hospital discharge, breastfeeding and maternal ethnicity as a potential marker of differential exposure to risk factors. Results: Independent risk factors for hospitalisation included low maternal SES (rate ratio: 1.33 [95% CI 1.19–1.49]); smoking (1.3 [1.19–1.41]); parity (2.77 [2.37–3.24]); preterm birth (3.14 [2.58–3.83]; 30 compared with 40 weeks); but not breastfeeding (0.99 [0.87–1.11]). After adjustment for risk factors, respiratory hospitalisations remained highest among infants of young Māori women (rate ratio 1.93 [1.46–2.55] at age 22.5 years) and Pacific women across all maternal age groups (rate ratios 2.43 to 2.55), compared with infants of European women. Conclusions: Maternal and birth factors are strongly associated with ethnic disparities in infant hospital admissions for respiratory disease. Implications: Interventions that begin in pregnancy and address risk factors and social determinants of health are needed to address these disparities.     

The Greek National Perinatal Survey. II: Socioeconomic factors and perinatal mortality in Greece

Information concerning all 10,859 singleton deliveries in Greece in April 1983, were analysed to assess the contribution of socioeconomic factors to the perinatal mortality rate. Statistically significant associations were initially found with parental education, parental ages, duration of marriage, paternal occupation and parity. There was no association with maternal smoking habit, maternal occupation during pregnancy, type of health insurance or housing conditions. Once logistic regression analyses had taken account of the strong parity effect (P less than 0.0001), only a moderate association with maternal age (P less than 0.05) remained statistically significant, together with a marginally significant (P less than 0.05) association with maternal education level. Mothers who were moderately well educated had the lowest risk of loosing their baby. It is concluded that traditional measures of social deprivation appeared to have little effect on perinatal mortality in Greece in 1983.