Higher Rates Of Preterm Delivery Research Articles

The Problem of Low Birth Weight

Low birth weight is a major public health problem in the United States, contributing substantially both to infant mortality and to childhood handicap. The principal determinant of low birth weight in the United States is preterm delivery, a phenomenon of largely unknown etiology. Preterm delivery is more common in the United States than in many other industrialized nations, and is the factor most responsible for the relatively high infant mortality rate in the United States. Within the United States, Asian populations experience the lowest preterm delivery rates, while Hispanic and Native American populations experience slightly higher preterm delivery rates than the white population. African Americans, however, have much higher rates of preterm delivery than any of the other major ethnic groups. Poverty is strongly and consistently associated with low birth weight, but the precise social and environmental conditions that produce preterm delivery have not been elucidated. Although it is popular to link illicit drug use to low birth weight, a high low birth weight rate was characteristic of the United States for decades before the cocaine epidemic of the 1980s. Neither the low birth rate nor the preterm delivery rate has improved in the United States in the past quarter century. Most efforts to prevent prematurity or low birth weight, when carefully evaluated, have not proven effective. A major goal of biomedical research ought to be better understanding of the causes of this important public health problem.

The Incidence of Histological Chorioamnionitis in IVF/GIFT Preterm Births

A retrospective case control study was designed to investigate the role of subclinical infection as a risk factor for the high rate of preterm deliveries in IVF/GIFT pregnancies. The cases and the controls were identified from the records of consecutive livebirths of < 35 weeks' gestational age (GA), at King George V Hospital from 1987-1993. Fifty one singleton and 58 twin IVF/GIFT preterm births were matched for GA, year of birth, plurality, maternal age, parity, preclampsia and antepartum haemorrhage. As a marker of subclinical infection, the incidence of histological chorioamnionitis (HCA) in the 2 groups (as defined by the standardized, semiquantitative method of Benirschke) was compared. The matched variables did not differ significantly between the IVF/GIFT group and the control group. No significant difference in the incidence of HCA was detected between IVF/GIFT and control groups for singletons or twins. Overall 24% of IVF/GIFT and 30% of controls showed evidence of HCA, odds ratio (95% confidence intervals), 0.72 (0.40-1.31). This study showed no evidence that the incidence of HCA, is significantly increased in IVF/GIFT preterm births compared with other matched, preterm births. Therefore, we conclude that subclinical infection/inflammation cannot explain the 4-fold increase in preterm births in the IVF/GIFT population.

Appraisal of in vitro fertilization

In-vitro fertilization and embryo transfer techniques are now used all over the world (53 countries). The results of 492 of all world units were collected from national surveys and registries of different countries. Since 1985, more than 53 635 women were treated and 34 316 babies were born by 224 473 treatment cycles, followed by more than 160 518 transfer cycles. Only about 65%–75% of all resulting pregnancies attained live births. The remainder ended with spontaneous abortions (26%), or ectopic pregnancies (5.54%). The multiple pregnancy rate (22%) was higher than the normal population and contributed to higher rates of preterm deliveries and perinatal mortality. No increased incidence of chromosomal aberrations and malformations were noted during the years (2.25%). Success rates did not improve significantly within the 5-year period surveyed, in most parts of the world. The indications for treatment were broadened during the years and the procedure became a final step for diagnosis and treatment of unexplained infertility. We conclude that IVF/ET is not an empirical treatment anymore and is a relatively safe procedure, although it should be used only when properly indicated. Male infertility and infertility of unexplained origin may be accepted indications for IVF/ET. More research and centralization of treatment in fewer but large units should be established in order to improve success rates and lower the cost per live birth child. Quality control by professional or public associations should be regulated.

Prognosis for pre-eclampsia complicated by 5 g or more of proteinuria in 24 hours

Forty-two women with pregnancies complicated by pre-eclampsia and heavy proteinuria ⩾5 g/24 h were referred for conservative management to the high-risk obstetric unit in the John Radcliffe Hospital, Oxford, over a period of 5 years. Hyperuricaemia preceded the onset of heavy proteinuria in all 42 women. Most of the women had severe hypertension, but none developed eclampsia and there were no major maternal complications. Delivery was necessary within 2 weeks of onset of severe proteinuria in 88.1% of cases, although in some very preterm pregnancies delivery could be deferred for 3 or more weeks. Thirty-five women (83%) were delivered by caesarean section, 91% of whom were delivered urgently before the onset of labour. The high rate of urgent preterm operative delivery underlines the uncertainty of advanced pre-eclampsia and the need for close monitoring if delivery is to be deferred. Perinatal mortality was high; all the perinatal deaths occurred in babies of less than 29 weeks gestation. Despite heavy proteinuria, postpartum recovery was good. Three months after delivery, all but one patient had no significant proteinuria. There was no evidence of residual renal dysfunction. Although the outlook for pre-eclampsia with heavy proteinuria is limited, in a few cases pregnancy can be prolonged for significant periods of time without apparently prejudicing maternal safety and permitting enhancement of maturity at birth. The observations justify cautious conservative management even when heavy proteinuria is present.

Teenage Pregnancy in Scotland: Trends and Risks

Teenage pregnancy, considered to be associated with social and medical risks, is seen as a growing problem. Population based information from the Registrar General (Scotland) and Notification of Abortion permitted an analysis of the trends in the numbers, rates and outcomes of pregnancies among women aged less than 20 years. In addition, clinical information is available on all deliveries in Scottish hospitals from the standard hospital discharge document permitting analysis of the association of defined complications with age. Contrary to current perceptions, pregnancies and births among teenagers are not more frequent in 1988 when compared to 1975. There has been, however, a large increase in births to single women, a group with particular problems. The obstetric risks when compared to older women, are small and probably socially, not age related. These include a slightly higher rate of pre-term delivery and low birthweight and a later presentation for specialist antenatal care. The proportion of pregnancies affected by neural tube defects which are terminated is lower among women under 20. These medical risks are small, however, compared to the well-documented social and economic problems which will have long term and indirect effects on health.

An indicator of adverse pregnancy outcome in France: not receiving maternity benefits.

The aim was to compare the social characteristics, the pregnancy outcome, and the antenatal care of women in France who did not receive maternity benefits to women who did. These benefits (860 FF, approx 86 pounds per month) are given to every pregnant woman, starting in the second trimester. Payments are made on the condition that at least three antenatal visits are made, the first being before the end of the first trimester. The study involved a random sample of women who were interviewed after delivery during their stay in hospital. Data on pregnancy outcome were collected from medical records. The study was carried out in four public maternity units in different regions of France. 1692 women were included in the analysis (86.8% of the selected sample). Of 257 exclusions, 40 had multiple pregnancies, 189 had missing data, and 28 did not answer the question concerning maternity benefits. 4.3% of the women did not receive any maternity benefits. These women lived in poorer social conditions than the women who received the benefits. They had a higher preterm delivery rate, after controlling for risk factors in a logistic regression. Women without maternity benefits were characterised by a lower level of care, yet the majority began their antenatal care during the first trimester or had more than six visits. Not receiving maternity benefits during pregnancy is an index of an underprivileged situation and a risk factor for pregnancy outcome.

Racial differences in pregnancy duration and its implications for perinatal care

The average length of gestation is about 5 days shorter in black populations than in white populations. Although some of this difference is accounted for by higher preterm delivery rates in blacks, the most common gestational week of delivery at term is the 39th in black populations, the 40th in white. Black gestational age specific neonatal mortality is lower than that of whites until the 37th week of gestation, but higher thereafter. These observations suggest the hypothesis that complications of postmaturity occur sooner in black fetuses. If this hypothesis is confirmed, antepartum surveillance for signs of fetal compromise should be initiated earlier in gestation in black parturients, perhaps by setting the estimated date of confinement at 275 days after the LMP, rather than the conventional 280 days.

Marital status and cohabitation during pregnancy: relationship with social conditions, antenatal care and pregnancy outcome in France.

A survey of a representative sample of 5508 births in France in 1981 permitted the study of social characteristics of pregnant women, the medical care they received during their pregnancy and their pregnancy outcome, as a function of their marital status and whether or not they lived with the father of the child. Unmarried women living with the father (n = 412) like unmarried women living alone (n = 171), were more often younger, having their first baby and had a lower educational level than did married women living with the father (n = 4590). However, among the unmarried women, those living alone were in a more unfavourable position than those living with the father; in particular, they were more often less than 20 years old, had the minimum educational level required and were unemployed. Both groups of unmarried women had a higher preterm delivery rate than did married women, even after taking other risk factors into account in a logistic regression. The odds ratios (95% confidence interval) for pre-term delivery among unmarried mothers living without the father was 1.9 (1.0-3.4) and that for the unmarried cohabiting with the father was 1.6 (1.0-2.4). Thus, to fully appreciate the perinatal risks and medical needs during pregnancy, both the marital and cohabitational status of the women should be considered.

Healthy worker effect and pregnancy: role of adverse obstetric history and social characteristics.

Data from a survey conducted in 1981 on a national sample of 5508 births in France were used to analyse the role of a history of previous adverse pregnancy outcome (spontaneous abortion, perinatal death or adverse fetal condition) in the selection mechanisms of women with regard to occupational activity, and the impact on the relation between work and preterm delivery. The study, carried out separately in each parity group, showed that occupational activity was associated with a more favourable outcome for women of parity one: the preterm delivery rate was significantly higher among women who had never worked than among those who continued working during pregnancy. However, the hypothesis of a "healthy worker effect" linked to a history of adverse obstetric outcome was not confirmed in this study. A selection effect of women from a history of spontaneous abortions was observed, but these were not linked to preterm delivery. Among multiparous women, a history of perinatal death or adverse fetal condition did not seem to modify women's behaviour towards their work. Selection mechanisms of women towards occupational activity according to sociodemographic factors were also analysed and showed that the higher percentage of younger women among those who had never worked explained the higher rate of preterm delivery in that group.

Pregnant women's working conditions and their changes during pregnancy: a national study in France.

In a study of 2387 employed women who had worked for more than three months of their pregnancy the data were extracted from a survey carried out on a national sample of births in France in 1981. Manual, service and shop workers had a higher preterm delivery rate than professional, administrative, or clerical workers. Assembly line work was associated with a higher preterm delivery rate even when production workers only were considered. Cumulated physically tiring working conditions--standing work, carrying of heavy loads, assembly line work, and considerable physical effort--were related to higher preterm delivery and low birthweight rate. During pregnancy, sickness absences were commoner when the working conditions were arduous. Changes in the working conditions were less clearly related to arduous work than sick leaves; they were not significantly more frequent for standing work or for assembly line work. Refusals from employers to grant favourable arrangements were more frequent when the working conditions were tiring and sick leaves were more common among women whose requests had been refused.

Ultrasound evaluation of polyhydr amnios and twin pregnancy

We analyzed the ultrasound examinations and medical records of 75 pairs of twins who were delivered between January, 1983, and December, 1984, to study the relationship between increased amniotic fluid volume, fetal abnormalities, and preterm labor. Ten of these 75 twin pregnancies demonstrated elevated amniotic fluid volume that persisted throughout pregnancy. Total intrauterine volumes were elevated in these cases, and nine of the ten pregnancies were abnormal. In addition, it was noted that elevation of the amniotic fluid volume alone did not explain the high rate of preterm labor and delivery in twin gestations.

Epidemiology of pregnancies with unknown last menstrual period.

A group of women with unknown last menstrual period was studied representing 16% of a total of 22 404 pregnant women recorded using a common perinatal form. Unknown menstrual period is associated with high rates of low birth weight and with low socioeconomic and sociodemographic status. Such characteristics are also associated with a high rate of preterm deliveries. Thus any possible bias introduced in studies of prematurity by ignoring the group of women with unknown last menstrual period should be carefully checked.

Epidemiological observations of thrombo-embolic disease during pregnancy and in the puerperium, in 56,022 women

During a 28-year period the incidence of thrombosis and pulmonary embolism (TE) in pregnancy remained practically equal (0.7‰), the incidence of puerperal TE was higher (2.3‰) but decreased during the last 7 years. Puerperal TE was influenced by age, mode of delivery, hypertension and prophylactic anticoagulant therapy. TE during pregnancy was not noticeably correlated with age and hypertension. TE during pregnancy and in the puerperium are closely related diseases, but their epidemiological characteristics are apparently distinct. Both are associated with a high rate of preterm deliveries and a high perinatal mortality rate.

Factors associated with preterm labour and changes in the cervix before labour in twin pregnancy.

A total of 132 twin pregnancies in black African women were studied prospectively after 30 weeks gestation. Delivery occurred before 37 weeks in 32%. There was a trend (0.1 greater than P greater than 0.05) towards a higher preterm delivery rate in nullipara (57%), in women under the age of 20 years (60%) and in those with a height/weight ratio of greater than 2.5 (50%). The cervix was assessed with a score based on the length of the canal minus the dilatation of the internal os. In both term and preterm labour there was a significant relation between a cervical score of 0 or a decrease in cervical score and the onset of labour within the subsequent 14 days (P less than 0.001). By these criteria to predict impending labour, 60% of all labours that ensured within 14 days of the assessment would have been predicted with a 20% false positive rate. When nulliparae were excluded the predictive value of cervical assessment for preterm labour was 80% with a false positive rate of less than 5%. Plasma oestriol levels were significantly higher in the preterm labour group but had no clinical prognostic value.