Invited commentary: Rare side effects of obstetric interventions: are observational studies good enough?
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Bias↗
Biomedical subjects
P Buekens
Publications and source records attributed to P Buekens.
Why do Mexican Americans give birth to few low-birth-weight infants?
There are relatively few low-weight births among Mexican Americans, despite their socioeconomic disadvantages. Fewer low-birth-weight (LBW) births result when babies are heavier at term or when there are fewer preterm deliveries. The authors used 1994 US singleton livebirth birth certificates to compare Mexican Americans with non-Hispanic Whites. They found that the lower LBW rate among Mexican Americans (5.8%) compared with non-Hispanic Whites (6.1%) occurred because fewer small, preterm babies were born to Mexican Americans (3.4% vs. 3.9%). This result was obscured by two findings. First, the mean birth weight of Mexican American babies (3,343 g) was lower than that of non-Hispanic White babies (3,393 g). This finding again showed the independence of mean birth weight and LBW. Second, the overall preterm birth rate was higher among Mexican Americans (10.6%) than non-Hispanic Whites (9.3%). Our hypothesis is that this finding reflects errors in recorded gestational age, as illustrated by a strongly bimodal birth-weight distribution at young gestational ages for Mexican Americans. Further studies on the LBW paradox among Mexican Americans should thus focus on gestational age more than on birth weight.
Adolescent↗
Trends in twin birth outcomes and prenatal care utilization in the United States, 1981-1997.
CONTEXT: Multiple births account for an increasing percentage of all low-birth-weight infants, preterm births, and infant mortality in the United States. Since 1981, the percentage of women with multiple births who received intensive prenatal care (defined as a high number of visits, exceeding the recommendation of the American College of Obstetricians and Gynecologists by approximately 1 SD beyond the mean number of visits for women initiating care within each trimester) has increased significantly. OBJECTIVES: To explore the hypothesis that more aggressive management of twin-birth pregnancies may be associated with changes in birth outcomes in this population. DESIGN, SETTING, AND SUBJECTS: Cross-sectional and trend analysis of data from the National Center for Health Statistics' birth and infant death records for all twin births occurring in the United States between 1981 and 1997, excluding those with missing or inconsistent data. MAIN OUTCOME MEASURES: Trends in preterm birth, low birth weight, preterm and term small-for-gestational-age (SGA) births, and infant mortality, by level of prenatal care utilization. RESULTS: The preterm birth rate for twins increased from 40.9% in 1981 to 55.0% in 1997. The percentage of low-birth-weight infants increased from 51.0% to 54.0%. The preterm SGA rate also increased from 11.9% to 14.1%, while the term SGA rate decreased from 30.7% to 20.5%. For women with intensive prenatal care utilization, the preterm birth rate increased from 35.1% to 55.8%, compared with an increase from 50.6% to 59.2% among women with only adequate use. Twin preterm deliveries involving either induction or first cesarean delivery also increased from 21.9% to 27.3% between 1989-1991 and 1995-1997. The twin infant mortality rate for women with intensive prenatal care use declined between 1983 and 1996 and remained lower than the overall twin infant mortality rate. CONCLUSIONS: An apparent increase in medical interventions in the management of twins may result in the seeming incongruity of more prenatal care and more preterm births; however, these data suggest that women with intensive prenatal care utilization also have a lower infant mortality rate. JAMA. 2000;283:335-341
Cross-Sectional Studies↗
Anemia during pregnancy and birth outcome: a meta-analysis.
To determine the relationship between maternal anemia [hemoglobin (Hgb) < 10-11 g/dL] and various birth outcomes, a meta-analysis was conducted based on published literature identified by MEDLINE and manual search from 1966 through 1999. Odds ratios (OR) from selected studies were pooled according to the gestational age at anemia diagnosis. The meta-analysis shows that maternal anemia during early pregnancy was associated with slightly increased preterm birth [pooled adjusted OR (aOR): 1.32, 95% confidence interval (CI): 1.01-1.74], and nonstatistically significant increased low birth weight [pooled aOR: 1.39 (0.70-2.74)], and was not associated with fetal growth restriction [pooled aOR: 1.01 (0.73-1.38)]. However, there was a nonstatistically significant inverse relationship between anemia during late pregnancy and preterm birth [pooled aOR: 0.92 (0.54-1.84)] and low birth weight [pooled aOR: 0.80 (0.64-1.00)]. Anemia was not statistically significantly associated with hypertensive disorders of pregnancy regardless of stage of pregnancy [pooled OR: 0.80 (0.53-1.20)]. The relationship between anemia and perinatal mortality was inconclusive. A few studies indicated that severe maternal anemia (Hgb < 8-8.5 g/dL) was associated with increased risk of poor outcomes. We conclude that early pregnancy anemia is associated with slightly increased risk of preterm birth. The trend toward an inverse association of anemia determined during late pregnancy with preterm birth and low birth weight may reflect the benefit of plasma volume expansion.
Adult↗
Association of preeclampsia with high birth weight for age.
OBJECTIVE: The purpose of this study was to examine the effect of gestational hypertension and preeclampsia on fetal growth. STUDY DESIGN: A retrospective cohort study was conducted on the basis of 97,270 pregnancies delivered between 1991 and 1996 in 35 hospitals in northern and central Alberta, Canada. Univariate and multivariate logistic analyses were performed to examine the impact of preeclampsia and gestational hypertension on high-birth-weight (> or =4200 g), large-for-gestational-age, low-birth-weight (<2500 g), and small-for-gestational-age babies. RESULTS: The rate of high-birth-weight fetuses in women with gestational hypertension (7. 3%) was higher than in those with normal blood pressure (5.6%). After we controlled for confounders, the adjusted odds ratio of high birth weight was 1.44 (95% confidence interval, 1.21-1.70) in women with gestational hypertension. Preeclampsia was also associated with a statistically nonsignificant (P =.054) increased risk of high birth weight (adjusted odds ratio, 1.40; 95% confidence interval 0. 99-1.98). The rate of large-for-gestational-age babies was significantly higher in women with gestational hypertension (4.5%) and preeclampsia (4.7%) than in those with normal blood pressure (2. 2%), with adjusted odds ratios of 1.50 (95% confidence interval, 1. 22-1.85) for gestational hypertension and 1.87 (95% confidence interval, 1.31-2.67) for preeclampsia. Concurrently, women who had gestational hypertension were also at higher risk of having low-birth-weight (adjusted odds ratio, 2.4; 95% confidence interval, 2.13-2.93) and small-for-gestational-age (adjusted odds ratio, 2.04; 95% confidence interval, 1.68-2.48) babies. Women with preeclampsia were also at markedly higher risk of having low-birth-weight (adjusted odds ratio, 4.14; 95% confidence interval, 3.32-5.15) and small-for-gestational-age (adjusted odds ratio, 2.56; 95% confidence interval, 1.92-3.41) babies. CONCLUSIONS: There is a significant association of preeclampsia and gestational hypertension with large-for-gestational-age infants, in addition to a significant association with low-birth-weight and small-for-gestational-age infants. This study challenges the currently held belief that reduced uteroplacental perfusion is the unique pathophysiologic process in preeclampsia.
Birth Weight↗
Disparity in prenatal care in Europe. Study group on barriers and incentives to prenatal care in Europe.
OBJECTIVE: The purpose of the study was to compare prenatal care attendance in European Union countries, Hungary and Norway. STUDY DESIGN: We analysed live births or deliveries from national registers in five countries, national surveys in five countries, and regional register or surveys in three countries. RESULTS: The frequency of no prenatal care was lower than 0.5% in 10 countries, 0.9% in Hungary, 2.1% in Greece and 2.6% in Portugal. Late prenatal care varied from 3.1% in Finland to 29.2% in Ireland. Late care among women with parity 4 and more varied from 7.7% in Finland to 41.5% in Hungary. Among women under 20 years old, late care varied from 11.8% in Finland to 39.5% in Portugal. The median number of prenatal visits varied from seven in Greece to 14 in Finland. CONCLUSION: Prenatal care attendance varies widely among European countries. Late attendance is frequent in many countries.
Europe↗
Birth outcomes of immigrant women in the United States, France, and Belgium.
OBJECTIVES: To compare maternal characteristics and birth outcomes of Mexico-born and native-born mothers in the United States and those of North African mothers living in France and Belgium to French and Belgian nationals. METHODS: We examined information from single live birth certificates for 285,371 Mexico-born and 3,131,632 U.S.-born mothers (including 2,537,264 U.S.-born White mothers) in the United States, 4,623 North African and 103,345 Belgian mothers in Belgium, and a French national random sample consisting of 632 North African and 11,185 French mothers. The outcomes were mean birthweight, low birthweight, and preterm births. Differences between native/nationals and foreign-born mothers in each country were assessed in bivariate and multivariate analyses controlling for maternal risk factors. RESULTS: The adjusted odds for low birthweight were lower for immigrants than native/nationals by 32% in the United States, by 32% in Belgium, and by 30% in France. The adjusted odds for preterm births were lower for immigrants compared with native/nationals by 11% in the United States and by 23% in Belgium. In France, the odds for preterm births were comparable for immigrants and naturalized mothers. Infants of immigrant mothers also had higher mean birthweights in all three countries. CONCLUSION: Despite their disadvantaged status, Mexico-born and North African-born women residing in the United States, France, and Belgium show good birth outcomes. These cannot be explained solely by traditional risk factors. Protective factors and selective migration may offer further clues.
Adolescent↗
Depressive symptoms are often unrecognized in gynaecological practice.
We performed a study on depressive symptoms in gynaecological practice in Belgium, identifying depressive symptoms according to both practitioners' opinions and the scores on a scale developed to detect depression in general medical settings. According to the 170 participating gynaecologists, 12% of the 2174 women they interviewed had symptoms of depression. However, 35% had two or more positive answers on the Depression Scale, and 19% had four or more positive answers. Our results suggest that depressive symptoms are often not identified in clinical gynaecological practice.
Adult↗
High birthweights among infants of north African immigrants in Belgium.
OBJECTIVES: This study examined birthweights of North African immigrants in Belgium. METHODS: Analyses focused on Belgian single live birth certificates from 1981 to 1988. RESULTS: Low-birthweight (< 2500 g) rates were 3.1% among 34,686 newborns of North African origin and 4.8% among 804,286 newborns of Belgian origin. The entire North African birthweight distribution was shifted toward higher birthweights than the Belgian distribution. Low frequencies of low birthweights among North Africans were still observed after marital status, occupation of the father, and parity had been taken into account. CONCLUSIONS: Despite their low socioeconomic status, North African immigrants have high birthweights.
Africa, Northern↗
Prenatal care incentives in Europe. Study Group on Barriers and Incentives to Prenatal Care in Europe.
The purpose of the study was to identify prenatal care incentives and benefits in 17 European countries. All participating countries completed a questionnaire on their prenatal care delivery system, incentives and benefits. Results were analyzed according to their direct or indirect relationship with prenatal care attendance. Direct incentives require a prenatal care visit to be eligible for the benefit. Indirect incentives support the pregnant woman but do not require a prenatal care visit to be eligible for the benefit. All 17 countries offer direct incentives, such as paid maternity leave. In 9 countries, pregnant women receive direct financial incentives. Eleven countries offer indirect incentives, such as transportation benefits. Prenatal care incentives such as financial benefits and social supports are widespread in Europe. The combination of incentives superimposed upon an inclusive health care system create a supportive environment which encourages prenatal care attendance.
Delivery of Health Care↗
Birth weight and perinatal mortality. A comparison of the United States and Norway.
OBJECTIVE: To compare perinatal mortality in the United States and Norway, using a new analytic approach based on relative birth weight. DESIGN: Comparison of linked birth and perinatal death records for US and Norwegian births from 1986 through 1987, the most recently available 2-year period. SETTING: Norway and the United States. PARTICIPANTS: A total of 7,445,914 US births and 105,084 Norwegian births. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Perinatal weight-specific mortality after adjustment for each country's own mean birth weight. RESULTS: The higher rate of perinatal death in the United States compared with Norway is due to an excess of preterm deliveries in the United States. Low-weight, preterm births comprise 2.9% of US births compared with 2.1% of Norwegian births. If the United States could eliminate this slight excess of preterm delivery, perinatal mortality in the United States would decrease to the level in Norway. Unexpectedly, the survival of newborns at any given birth weight is virtually the same in the United States and Norway when newborns' birth weights are considered relative to their own nation's mean weight. CONCLUSIONS: Low rates of perinatal mortality in the Scandinavian countries have usually been attributed to the heavier weights of their newborns. Higher mortality among US infants is in fact due entirely to a small excess of preterm deliveries. The lighter weights of US newborns at term appear not to affect perinatal survival. Furthermore, the apparent survival advantage of low-weight US newborns (used by policymakers as evidence of superior US intensive neonatal care) may be at least partly an artifact. When weight-specific mortality rates are adjusted to relative birth weight, low-weight newborns have the same survival in Norway as in the United States. The prevention of excess mortality among US infants depends on the prevention of preterm births, not on changes in mean birth weight.
Birth Weight↗
IUD use and the risk of ectopic pregnancy: a meta-analysis of case-control studies.
Because of inconsistent findings among case-control studies on the relationship between IUD use and the risk of ectopic pregnancy, a meta-analysis of published literature was conducted. From 1977 through 1994, 19 publications regarding 16 studies of ectopic pregnancy and IUD use were found by MEDLINE and manual search. The odds ratio (ORs) of ectopic pregnancy with current and past IUD use in each study were pooled. A quality score system was developed to assess each study. Funnel plot was used to assess potential publication biases. For current IUD use, when cases were compared to pregnant controls, there was an increased risk of ectopic pregnancy (pooled OR: 10.63, 95% confidence interval (CI): 7.66-14.74); when cases were compared to non-pregnant controls, there was no risk of ectopic pregnancy (pooled OR: 1.06, 95% CI: 0.91-1.24). Past IUD use could mildly increase the risk of ectopic pregnancy (pooled OR: 1.40, 95% CI: 1.23-1.59). Selecting pregnant or non-pregnant women as controls, however, did not affect the OR estimates of past IUD use. Current IUD use does not increase the risk of the ectopic pregnancy. However, a pregnancy with an IUD in situ is more often an ectopic one than a pregnancy with no IUD. Past IUD use could mildly elevate the risk of ectopic pregnancy.
Adolescent↗
Tetanus immunization and prenatal care in developing countries.
OBJECTIVE: We sought to estimate the proportion of women immunized against tetanus while attending prenatal care in the developing countries. METHOD: We computed the ratio of the percentage of births to women immunized against tetanus to the percentage of births to women with prenatal care (TP ratio). A TP ratio is lower than 100% if not every woman attending prenatal care is immunized. We used 1986-1992 Demographic and Health Surveys data from 38 countries. RESULTS: The mean TP ratios were 86% in Africa (n = 23), 79% in Asia (n = 6) and 60% in Latin American and the Caribbean (n = 9). The TP ratio was lower than 75% in 15 countries. Of these, four had a TP ratio lower than 50%. CONCLUSION: In many countries the number of pregnant women immunized against tetanus is lower than the number of women attending prenatal care, suggesting that prenatal services are missing opportunities to immunize attending women.
Developing Countries↗
Oxytocics in developing countries.
OBJECTIVES: A prospective multicenter study of obstetric practices was conducted in three developing countries (Benin, Congo and Senegal) to analyze oxytocic use during labor. One of the objectives was to assess the possible negative effects of the treatment regimens instituted during the labor monitoring phase. METHODS: Four health districts participated in the study. All women who gave birth in one of the participating health facilities over a 6-month period in Benin and Congo, and over a 3-month period in Senegal, were recruited. The number of deliveries studied in each district varied from 457 to 1048. For each case a partogram was used to assess the progress of labor and the onset of dysfunctional labor. Information was collected on the risk factors for dysfunctional labor, stillbirths and resuscitation of the neonate. RESULTS: Each of the four collaborating centers used oxytocics preferentially to treat dysfunctional labor, but even in normal labor (i.e. with a normal partogram) oxytocics were used in 4.4-21.5% of cases. In normal labor the incidence of neonatal resuscitation was higher in cases with than in those without oxytocic use: the relative risks (R.R.) varied from 1.9 to 5.6; the odds ratios varied from 2.4 to 7.0, and both were statistically significant in the four settings. In addition the stillbirth rate was always higher, though not significantly, when oxytocics were used in normal labor (R.R. 1.2-2.2). When the data of the four centers were pooled, the global relative risk for stillbirths was 1.9, and the 95% confidence interval was 1.1-3.4. Logistic regression analysis was carried out for five confounding factors (primiparity, a previous complicated delivery, presence of meconium, ruptured membranes and educational level) to adjust the odds ratio for the risk of neonatal resuscitation when oxytocics were used in normal labor. Except in the case of Abomey in Benin, where the variable 'presence of meconium' decreased the odds ratio from 6.4 to 3.4, the adjusted odds ratios remained similar to their non-adjusted values. In cases of non-dysfunctional labor, nurses and midwives used oxytocics more often than lesser trained health personnel (R.R. 4.0 [3.2-5.1]). CONCLUSION: Our results show that an obstetric treatment which is safe when used in certain well-defined indications, may have significant negative effects when used in situations where the same technical quality of care cannot be guaranteed.
Developing Countries↗
Birthweight, preterm births and neonatal mortality in Belgium and the United States.
Belgium is known to have a lesser low birthweight rate and a lower infant mortality rate than the United States. We used previously unpublished data to show that beneath this comparison lies a more complicated picture. Singleton live birth certificates for 1986-87 were analysed. Despite a lower mean birthweight in Belgium (3360 g) than in the United States (3420 g), Belgium had fewer (4.9%) low birthweight infants than the US (5.9%) because of fewer preterm births (4.4 vs. 9.3%). Consistent with the excess of preterm births in the US, the residual distribution of birthweight was smaller in Belgium (2.2% vs. 3.1%). Whereas neonatal mortality was 4.8/1000 in Belgium and 5.6/1000 in the US, birthweight-specific neonatal mortality was higher in Belgium. The challenge for Belgium is to improve the survival of newborns regardless of their birthweight. In the US, the task is to eliminate the excess of small preterm infants.
Belgium↗
Chaos theory in obstetrics and gynaecology.
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Gynecology↗
[Levels of low birth-weight in Europe: registration problems and effects of medical interventions].
The rate of low birthweight births, percentage of live births weighing less than 2500 grams is one of the perinatal health indicators recommended by the World Health Organisation. A review of the literature has revealed numerous problems related to this indicator. Some countries, including France and the Netherlands do not collect birthweight data. Elsewhere, there are more than 10% "unknown birthweight". The poorest registration is for birthweights below 1000 grams. Exclusion of babies who were registered as stillborn, when in fact they died shortly after birth can cause underregistration of low birthweights. Conversely, inclusion of true stillbirths will bring on an overestimation of low birthweight rate. Some countries have too few births to deliver accurate rates. Rates of medical interventions, such as infertility treatment and elective induction should be taken into account when analyzing differences between countries. Improvement in quality of registration and caution in the use of this indicator are warranted.
Bias↗