Higher Risk Of Low Birth Weight Research Articles

Air Pollution and Adverse Pregnancy Outcomes: What is the Role of Gender? A Systematic Review

SAA5-O-05 Introduction: Gender differences in pregnancy outcomes, eg, low birth weight (LBW), preterm birth (PTB), and fetal growth retardation are well established. Recent studies on air pollution and adverse pregnancy outcomes suggest an increase in risk, albeit small. We undertook a systematic review to study the interaction between gender and air pollution on pregnancy outcomes. Methods: English language articles were retrieved from Medline, Embase, Science Citation Index, and other environmental databases using a comprehensive list of key words relating to gender, air pollution, and pregnancy outcomes (1966–2005). Studies were included if: Exposure measurements were well defined: personal monitoring, approximation from ambient levels, modelled estimates and proximity to pollution sources; Pollutants were specified; Effects on pregnancy outcomes were reported; Effect estimates were reported by gender. Studies were excluded if they included accidental or occupational exposures and multiple births. A tailored checklist based on Bracken's Guideline for Observational Studies, was used to assess methodologic quality. Quality was assessed based on the applicability of the findings and validity of the individual study results. We had concern about exposure measurements in 2 studies while some others did not adjust for socioeconomic status and maternal smoking. Overall the quality of the included studies was considered satisfactory. Results: A total of 11 studies, conducted between 1986 and 2003, were included. Of these, 4 evaluated LBW; one each evaluated very low birth weight (VLBW) and fetal growth, and 6 examined PTB. PTB studies were more homogeneous in terms of study design and analysis than the LBW studies. Female babies were at higher risk of LBW (AORs ranged from 1.07 to 1.62) and male babies were found to be at higher risk for PTB (AORs ranged from 1.11 to 1.20) from the adjusted logistic models. In addition, there was some evidence of an interaction between gender and air pollution for LBW when the highest and lowest exposure categories were compared separately for male and female babies. The risk of LBW, which is commonly high for female babies, was higher in males after accounting for interaction; however, the results were not statistically significant. Discussion and Conclusions: This review provides some limited evidence of an interaction between air pollution and gender on pregnancy outcomes. Any interactive effect should be interpreted with caution in light of study limitations, such as exposure misclassification, multiple comparisons, and residual confounding. Further studies using high quality datasets are needed to ascertain the effect.

Vanishing twin is associated with less favorable obstetric outcome compared to singleton pregnancies in women undergoing IVF-ET

COMPARED TO SINGLETON PREGNANCIES IN WOMEN UNDERGOING IVF-ET SONYA ABDEL-RAZEQ, MOHAMED MITWALLY, LAURA DETTI, MICHAEL SULLIVAN, KENT CRICKARD, MICHAEL DIAMOND, University at Buffalo, Gynecology and Obstetrics, Buffalo, New York, Wayne State University, Obstetrics and Gynecology, Bloomfield Hills, Michigan, Wayne State University, Department of Obstetrics and Gynecology, Detroit, Michigan, Wayne State University, Obstetrics/Gynecology, Detroit, Michigan OBJECTIVE: There is evidence that infertility treatment, including in vitro fertilization and embryo transfer (IVF-ET), is associated with less favorable obstetric outcome, specifically, higher pregnancy loss, preterm labor and low birth weight (BW). Vanishing-twin is a phenomenon in which one or more of implanted embryos fail to continue. We studied outcome of singleton pregnancies after vanishing-twin compared to pregnancies that started as singletons. STUDY DESIGN: Retrospective analysis of 61 consecutive live-births from singleton pregnancies in women undergoing IVF-ET. Five pregnancies started as twins and ended as singletons due to vanishing-twin; 56 pregnancies started as singletons. Vanishing-twin was diagnosed by ultrasound at 6-wks (2 gestational sacs with 2 heartbeats) followed by another ultrasound showing loss of one of the twins at 8 to 12 wks. Gestational age (GA) was calculated from ET day until delivery. BW was calculated as percentage from BW expected according to GA (expected BW was calculated from control population similar to Western New York region matching patients who underwent IVF-ET). RESULTS: Vanishing-twin pregnancies were associated with significantly lower BW and shorter GA. There was no significant difference regarding age, gravity, infertility factor and duration, ovarian stimulation protocol, or in vitro conditions (oocyte insemination, day and number of embryos transferred, fertilization or implantation rate). CONCLUSION: Pregnancies associated with vanishing-twin after IVF-ET are associated with higher risk for low BW and short GA.

Trends in prenatal care use and low birthweight in southeast Brazil.

We investigated trends in prenatal care use and its association with low birthweight in a developing country. We examined data from 2 southeast Brazilian cohort surveys, 1 conducted in 1978-1979 and the other in 1994. Socioeconomic inequalities in prenatal care use increased during the 15-year period of 1979-1994. Although prenatal care use increases paralleled increases in low birthweight rate during this period, having no prenatal care was associated with higher risk of low birthweight in both surveys. Inadequate prenatal care use was also associated with higher risk of low birthweight in 1978-1979 only. Increasing low birthweight rates among women who adequately used prenatal care may be causing a bias by reducing the estimates of the effect of inadequate prenatal care use on low birthweight rates.

Determinants of low birth weight among HIV-infected pregnant women in Tanzania

Low birth weight (LBW) increases the risk of infant death, but little is known about its causes among HIV-infected populations in sub-Saharan Africa. We assessed sociodemographic, nutritional, immunologic, parasitic, and infant risk factors for birth weight, LBW, and small-for-gestational-age (SGA) status in a cohort of 822 HIV-positive women enrolled in a clinical trial of vitamin supplementation and pregnancy outcomes in Dar es Salaam, Tanzania. Women were enrolled at prenatal care clinics during their second trimester, at which time blood, stool, urine, and genital specimens were collected, and anthropometric measurements and sociodemographic data were recorded. Birth weight was measured at hospital delivery. The mean (+/-SD) birth weight was 3015 +/- 508 g, 11.1% of newborns weighed <2500 g (LBW), and 11.5% were SGA. In multivariate analyses, maternal weight at enrollment and a low CD8 cell count were inversely associated with LBW. Advanced-stage HIV disease, previous history of preterm birth, Plasmodium falciparum malaria, and any helmintic infection were associated with higher risk of LBW. The intestinal parasites Entamoeba histolytica and Strongyloides stercoralis were predictors of LBW despite their low prevalence in the cohort. In a multivariate-adjusted linear regression model, BMI, midupper arm circumference, a CD4 cell count <200 x 10(6) cells/L (200 cells/mm(3)), primiparity, maternal literacy, and infant HIV infection at birth were significantly associated with birth weight in addition to risk factors included in the LBW model. Determinants of SGA included maternal weight, low serum vitamin E concentration, candidiasis, malaria, and infant HIV infection at birth. Prevention of HIV disease progression and vertical transmission, improved nutritional status, and better management of malaria and intestinal parasitic infections are likely to reduce the incidence of LBW in Tanzania.

The association between maternal HIV-1 infection and pregnancy outcomes in Dar es Salaam, Tanzania.

To examine the association between maternal HIV infection and pregnancy outcomes controlling for potential confounding factors among a cohort of HIV-uninfected and HIV-infected pregnant women in Dar es Salaam, Tanzania. Prospective cohort study. A cohort of 1,078 HIV-infected and 502 HIV-uninfected pregnant women between 12 and 27 weeks of gestation were enrolled and followed up until delivery. Multiple regression models were used to compare the risk of adverse pregnancy outcomes among HIV-uninfected women with those among HIV-infected women overall, and separately among asymptomatic or symptomatic HIV-infected women. No significant differences between HIV-uninfected women and HIV-infected women were observed in risks of fetal loss or low birthweight or in the weight, head circumference and gestational age of infants at birth. HIV-infected women were more likely to have severe immature infants (<34 weeks) than HIV-uninfected women (multivariate RR 1.54 [95% CI 0.90-2.48]; P= 0.05). There was a significantly higher risk of low birthweight (RR 2.29, 95% CI 1.34-3.92; P = 0.03) and prematurity (<37 weeks) (RR 1.93, 95% CI 1.35-2.77; P = 0.0003) among symptomatic HIV-infected women when compared with HIV-uninfected women. HIV-infected women, particularly those whoare symptomatic, are at a higher risk of adverse pregnancy outcomes.

The association between maternal HIV-1 infection and pregnancy outcomes in Dar es Salaam, Tanzania

Objective To examine the association between maternal HIV infection and pregnancy outcomes controlling for potential confounding factors among a cohort of HIV-uninfected and HIV-infected pregnant women in Dar es Salaam, Tanzania. Design Prospective cohort study. Methods A cohort of 1078 HIV-infected and 502 HIV-uninfected pregnant women between 12 and 27 weeks of gestation were enrolled and followed up until delivery. Multiple regression models were used to compare the risk of adverse pregnancy outcomes among HIV-uninfected women with those among HIV-infected women overall, and separately among asymptomatic or symptomatic HIV-infected women. Results No significant differences between HIV-uninfected women and HIV-infected women were observed in risks of fetal loss or low birthweight or in the weight, head circumference and gestational age of infants at birth. HIV-infected women were more likely to have severe immature infants (<34 weeks) than HIV-uninfected women (multivariate RR 1.54 [95% CI 0.90–2.48]; P=0.05). There was a significantly higher risk of low birthweight (RR 2.29, 95% CI 1.34–3.92; P=0.03) and prematurity (<37 weeks) (RR 1.93, 95% CI 1.35–2.77; P=0.0003) among symptomatic HIV-infected women when compared with HIV-uninfected women. Conclusion HIV-infected women, particularly those who are symptomatic, are at a higher risk of adverse pregnancy outcomes.

Birth weight trends among interracial black and white infants.

I examined time trends in low birth weight (LBW) and very low birth weight (VLBW) among interracial compared with single-race infants. Using natality data from 1978 through 1997 for singleton births to black and white parents, I calculated relative risks (RRs) of LBW and VLBW for interracial compared with single-race births, stratified by maternal race and adjusted for maternal characteristics. Among black mothers, interracial births had lower risks of LBW and VLBW than single-race births, and RRs were similar throughout the time period [for example, adjusted RR = 0.76 and 95% confidence interval (CI) = 0.73-0.80 for LBW in 1994-1997]. Among white mothers, interracial infants had higher risks of LBW than single-race infants; however, the adjusted RRs declined over the time period, from 1.22 (95% CI = 1.19-1.27) in 1978-1981 to 1.05 (95% CI = 1.03-1.08) in 1994-1997. Since 1978, there has been some relative improvement in birth outcomes for infants of white mothers and black fathers compared with single-race white births. There was, however, no relative improvement for black mother/black father infants relative to black mother/white father births.

The Latin American trial of psychosocial support during pregnancy: Effects on mother's wellbeing and satisfaction

A randomized controlled trial including 2235 women at high risk of low birthweight was conducted in four Latin American institutions. The objective of this trial was to evaluate a psychosocial support intervention during pregnancy aimed at improving perinatal health and mothers' psychosocial conditions. The core of the intervention was four to six home visits where emotional support, counseling and strengthening of the woman's social network was provided. Outcomes were measured at 36 weeks of pregnancy, post-partum and 40 days after delivery. The intervention was not successful in either altering women's perception of social support and satisfaction with the reproductive experience, as well as maternal and newborn's health care. It is concluded that although high levels of psychosocial distress during pregnancy may play an independent role in determining adverse pregnancy outcomes, this adverse effect does not appear to be ameliorated by psychosocial interventions conducted only during pregnancy, particularly those of a magnitude that can be realistically implemented (in content and frequency) at public care services in most developing countries.

Perinatal diagnostic evaluation of velamentous umbilical cord insertion: Clinical, doppler, and ultrasonic findings

To evaluate the association between velamentous cord insertion and adverse pregnancy outcome in singleton pregnancies, and to assess the diagnostic usefulness of nonstress testing (NST) and Doppler ultrasound in this condition. We retrospectively reviewed 12,750 consecutive singleton, chromosomally normal pregnancies from July 1989 through December 1993 at the University Hospital of Kuopio, Finland. Of these, 216 were complicated by velamentous umbilical cord insertion, whereas the remaining 12,534 were normal controls. Using multiple regression analysis, we evaluated the risks by noting adverse infant outcomes: low birth weight (LBW), small for gestational age (SGA), preterm delivery, fetal death, admission to a specific infant care unit, low Apgar scores, neonatal acidemia, and abnormal intrapartum fetal heart rate (FHR) patterns. At prenatal visits, NST and Doppler ultrasound examinations were carried out as a routine part of obstetric care. Even after we controlled for confounding factors, velamentous umbilical cord insertion was associated with higher risk of LBW (odds ratio [OR] 2.32), SGA (OR 1.54), preterm delivery (OR 2.12), low Apgar scores at 1 and 5 minutes (ORs 1.76 and 2.47, respectively), and abnormal intrapartum FHR pattern (OR 1.59). Only 5% of the patients with abnormal insertion showed pathologic NST results at prenatal visits. Ultrasonographic examination was carried out on 80 patients with velamentous umbilical cord insertion as a routine part of obstetric care, and in only one case was direct visualization of the abnormal insertion successful. After we excluded pregnancies with preeclampsia, abnormal umbilical artery Doppler velocimetry was found in none of the cases examined (n = 48). There were substantial differences in pregnancy outcome measures between the subjects with velamentous umbilical cord insertion and controls. Current antepartum methods of tracing uteroplacental problems are not effective in the prenatal detection of abnormal insertion. Therefore, in future studies, the use of other diagnostic tools, such as color Doppler imaging of cord insertion, should be evaluated in high-risk pregnancies followed-up because of fetal growth restriction.

Amount of Antenatal Care and Infant Outcome

The connection between the amount of antenatal care and pregnancy outcome was studied using the 1987 Finnish Medical Birth Registry. A total of 57 108 women were included in the analysis. The timing of initiation of antenatal care and the relative number of antenatal visits (adjusted by gestation length), were used as measures of amount of antenatal care. Nine outcome variables measuring infant health and interventions were studied. Logistic regression was used to adjust for differences in maternal background characteristics. Women beginning antenatal care after the 16th week of gestation had the poorest outcome. Early attending multiparous women had a higher risk of low birthweight, premature infants, caesarean section and instrumental delivery than did those with average timing of their first attendance. For primigravidas, the increased risk was of prematurity only. A U-shaped curve was found for most of the outcome variables in regard to relative number of visits. The women with many visits had the poorest outcome, and also the highest rates of caesarean section and induction of labour. One reason for the unexpectedly high risks for early attenders may be connected with the content of antenatal care. In Finland, it might be possible to reduce the total number of antenatal visits without having any negative effect on infant health.

The low birth weight hypothesis as a plausible explanation for the black/white differences in hypertension, non-insulin-dependent diabetes, and end-stage renal disease

It is well known that black Americans have a higher risk for low birth weight (LBW) than white Americans. In addition, blacks are at a higher risk for hypertension (HT), non-insulin dependent diabetes mellitus (NIDDM), and end-stage renal disease (ESRD), particularly ESRD attributed to HT (ESRD-HT) and NIDDM (ESRD-NIDDM). It has been shown that LBW is associated with postpartum anatomic and functional alterations in the kidney and pancreas as well as with progressive renal damage in animals and increased risk for HT and NIDDM during adulthood in humans. Based on these empirical findings, it is here proposed that a greater risk of HT, NIDDM, and ESRD, particularly ESRD-HT and ESRD-NIDDM, in black Americans during adulthood may be partly related to their higher risk of LBW. However, LBW is proposed here as a component factor rather than a sufficient cause or a necessary factor for the development of these diseases. The ultimate contribution of LBW to the black/white disparities regarding HT, NIDDM, and ESRD may depend not only on the black/white differences in LBW but also on the race-specific prevalences of other component factors, both environmental/behavioral and genetic, that may or may not require the presence of LBW to cause each of these diseases.

Amount of antenatal care and infant outcome

The connection between the amount of antenatal care and pregnancy outcome was studied using the 1987 Finnish Medical Birth Registry. A total of 57 108 women were included in the analysis. The timing of initiation of antenatal care and the relative number of antenatal visits (adjusted by gestation length), were used as measures of amount of antenatal care. Nine outcome variables measuring infant health and interventions were studied. Logistic regression was used to adjust for differences in maternal background characteristics. Women beginning antenatal care after the 16th week of gestation had the poorest outcome. Early attending multiparous women had a higher risk of low birthweight, premature infants, caesarean section and instrumental delivery than did those with average timing of their first attendance. For primigravidas, the increased risk was of prematurity only. A U-shaped curve was found for most of the outcome variables in regard to relative number of visits. The women with many visits had the poorest outcome, and also the highest rates of caesarean section and induction of labour. One reason for the unexpectedly high risks for early attenders may be connected with the content of antenatal care. In Finland, it might be possible to reduce the total number of antenatal visits without having any negative effect on infant health.

The effect of maternal age and socioeconomical background on neonatal outcome

This population-based study examined whether the neonatal outcome of primiparae is determined by maternal age or by her socioeconomic background. Data on all births in Israel during a three-month period was made available from a nation-wide census. Primiparae 30 years of age or older had a significantly (P < 0.001) higher risk of low birthweight and prematurity. Perinatal mortality rates and low 5-min Apgar scores were not associated with maternal age, but were significantly (P < 0.001) increased for the socioeconomically disadvantaged parturients. Our results suggest the growth retardation and short gestation among older primiparae may reflect biological aging of maternal tissues and the effect of diseases of pregnancy such as hypertension and preeclampsia, found significantly (P < 0.001) more common for these mothers. Excessive perinatal mortality, on the other hand, may be attributable to environmental disadvantage of socioeconomically deprived populations.

Could oedema and proteinuria in pregnancy be used to screen for high risk? The WHO International Collaborative Study of Hypertensive Disorders of Pregnancy.

Prospectively gathered data from eight geographically defined areas in south-east Asia included serial measures of blood pressure, proteinuria and oedema during pregnancy. A total of 15,476 pregnancies were included. Both antenatal oedema and proteinuria were markers of increased risk of antenatal diastolic hypertension, proteinuric pre-eclampsia and eclampsia. However they identified fetuses at high risk of low birthweight and perinatal mortality only in areas where the incidence of hypertension was low. As a screening strategy to identify women who are at increased risk of antenatal diastolic hypertension, of proteinuric pre-eclampsia and of eclampsia, the most efficient strategy is probably to use the presence of oedema and/or proteinuria. The sensitivity of using this method for identifying women with proteinuric pre-eclampsia is high, but for identifying eclampsia it is still relatively low. Where resources are available there is probably no substitute for using a sphygmomanometer and measuring blood pressure.

Teenage pregnancies in Western Australia.

Examination of fertility rates among teenagers in Western Australia from 1968 to 1978 revealed a steady decline n the birth rate among older teenagers (16-19); a similar decline did not occur among girls under 16. an increasing proportion of teenage births is occurring to these young teenagers. Information obtained from a linked file of birth and perinatal death registrations in Western Australia over the same period indicates that the infants of young teenage mothers have a substantially higher risk of low birthweight and perinatal death than infants of older mothers. The presence of this high-risk group of very young teenagers needs to be emphasized, as it is usually masked by presentation of data on all teenagers as a group. The authors recommended the involvement of special adolescent units in the prevention and management of teenage pregnancy.