Multivariate analysis of determinants of fetal growth retardation

Early pregnancy exposure to metal mixture and birth outcomes - A prospective study in Project Viva

BACKGROUND

Prenatal exposure to metals has been individually associated with birth outcomes. However, little is known about the effect of metal mixture, particularly at low exposure levels.

OBJECTIVES

To estimate individual and joint effects of metal mixture components on birth outcomes.

METHODS

We used data from 1,391 mother-infant pairs in Project Viva (1999-2002). We measured 11 metals in maternal 1st trimester erythrocyte; abstracted birth weight from medical records; calculated gestational age from last menstrual period or ultrasound; and obtained birth length (n = 729) and head circumference (n = 791) from research measurements. We estimated individual and joint effects of metals using multivariable linear and Bayesian kernel machine regressions.

RESULTS

In both single metal and metal mixture analyses, exposure to higher concentrations of arsenic was associated with lower birth weight in males, zinc with higher head circumference in females, and manganese with higher birth length in sex-combined analysis. We also observed sex-specific metal interactions with birth outcomes. Arsenic and manganese showed a synergistic association with birth weight in males, in whom an interquartile range (IQR) increase in arsenic was associated with 25.3 g (95% CI: -79.9, 29.3), 47.9 g (95% CI: -98.0, 2.1), and 72.2 g (95% CI: -129.8, -14.7) lower birth weight when manganese concentrations were at 25th, 50th, and 75th percentiles, respectively. Lead and zinc showed an antagonistic association with head circumference in males, where an IQR increase in lead was associated with 0.18 cm (95% CI: -0.35, -0.02), 0.10 cm (95% CI: -0.25, 0.04), 0.03 cm (95% CI: -0.2, 0.14) smaller head circumference when zinc concentrations were at 25th, 50th, and 75th percentiles, respectively. Exposure to higher concentrations of arsenic was also associated with lower gestational age in males when concentrations of manganese and lead were higher.

DISCUSSION

Maternal erythrocyte concentrations of arsenic, manganese, lead, and zinc were individually and interactively associated with birth outcomes. The associations varied by infant sex and exposure level of other mixture components.

Prenatal exposure to metal mixture and sex-specific birth outcomes in the New Hampshire Birth Cohort Study

BACKGROUND

In utero exposure to individual metals may impact fetal growth, though little is known about the effects of exposure to metal mixtures. Therefore, we investigated joint effects of in utero exposure to a mixture of As (arsenic), Mn (manganese), and Pb (lead) on newborn outcomes in a United States population.

METHODS

Concentrations of As, Mn, and Pb were determined in maternal postpartum toenail samples, a biomarker of in utero exposure, from 989 maternal-infant pairs (492 females and 497 males). Newborns' anthropometric characteristics, including head circumference, length, and weight, were obtained from medical records. The joint effects of the three metals were modeled using Bayesian kernel machine regression and linear regression. Both sex-combined and sex-stratified statistical analyses were performed.

RESULTS

We observed an inverted-U-shape association between maternal toenail Mn concentrations and newborn head circumference, particularly among female infants. Concentrations of Pb were related to reduced head circumference, weight, and length, especially among females at lower concentrations of the other metals. Overall, toenail As concentrations were related to reduced head circumference, especially among males, and an increase in birth length and weight among females. We found little evidence of As interactions with other metals within the mixture.

CONCLUSIONS

Our findings suggest that in utero metal mixture exposures may influence birth outcomes, and that such relations may differ by infant sex.

Care of Drug-Addicted Pregnant Women: Current Concepts and Future Strategies – an Overview

This review focuses on drug use during pregnancy and the perinatal period, a constellation that is seen more often. Drug use in pregnant women poses an increased risk for adverse health outcomes both for the mother and child. Care is often complicated by social and environmental factors, as well as psychiatric comorbidities. It is, therefore, very important to provide drug-using pregnant women with optimal ante-, peri- and post-natal care. Health professionals should approach them in a nonjudgmental and supportive way, and provide them with the same care and attention as nondrug-using women. Adequate care requires interdisciplinary teams. Ideally, healthcare providers should be specialized in the care of drug-using pregnant women.

Physical activity by pregnant women and outcomes for newborns: a systematic review

A systematic review was carried out aiming at analyzing daily physical activity during pregnancy and the outcomes of birth weight, prematurity, and intrauterine growth restriction. Of 52 articles indexed in Medline, 22 that showed better methodological quality were included. Among the 22 articles analyzed, only two did not detect a significant association between physical activity and the outcomes studied. There was large variation between the indicators of maternal physical activity, which included occupational, household, recreational and, all or some, locomotive activities. Among ten articles that measured total daily physical activity, only one article did not find any association. The results support the hypothesis that both excessive and insufficient physical activity impact negatively on pregnancy outcomes.

Genetic thrombophilias and intrauterine growth restriction: a meta-analysis

OBJECTIVE

To estimate the relationship between inherited thrombophilias and intrauterine growth restriction (IUGR) using meta-analytic techniques.

METHODS

A literature review identified case-control and cohort studies evaluating the relationship between IUGR and the following thrombophilias: homozygous or heterozygous factor V Leiden or prothrombin (PT) G20210A mutations and homozygous methylenetetrahydrofolate reductase (MTHFR) C677T mutation. Using mixed effects and random-effects models, the association between thrombophilias and IUGR was explored. Publication bias was assessed with funnel plots and corrected for with Duval and Tweedie's trim-and-fill method.

RESULTS

The following number of related studies were found: studies evaluating relationships between factor V Leiden mutation and IUGR, 12 case-control and four cohort; between PT mutation and IUGR, 11 case-control and 0 cohort; and between MTHFR C677T homozygosity and IUGR, 10 case-control and two cohort. The overall summary odds ratio (OR) for the association between factor V Leiden and IUGR was significant (OR 1.23, 95% confidence interval [CI] 1.04-1.44); however, this was mainly driven by the positive association seen in the case-control studies (OR 1.91, 95% CI 1.17-3.12). The association between PT and IUGR was only explored in case-control studies yielding a summary OR that was not significant (OR 1.52, 95% CI 0.98-2.35). The overall summary OR for the association between MTHFR and IUGR was not significant (OR 1.01, 95% CI 0.88-1.17), but was significant for the case-control studies alone (OR 1.35, 95% CI 1.04-1.75). For both factor V Leiden and MTHFR mutations, a funnel-plot analysis of the case-control studies suggests publication bias. When the trim-and fill-method was used to correct for the publication bias, these summary estimates were no longer significant.

CONCLUSION

The association between inherited thrombophilias and IUGR can only be discerned in case-control studies and seems to be largely because of publication bias.

LEVEL OF EVIDENCE

III.

Prediction and perinatal outcomes of fetal growth restriction

Assessment of fetal growth and wellbeing is one of the major purposes of antenatal care. Some fetuses have smaller than expected growth in utero and while some of these fetuses are constitutionally small, others have failed to meet their growth potential, that is they are growth restricted. While severe growth restriction is uncommon, the consequences of it being undetected may include perinatal death or severe morbidity. It is, therefore, important to have strategies in place to detect the fetus at risk of growth restriction. These would include an assessment of 'prior risk' from maternal history and examination combined with the results of biochemical and ultrasound investigations, the most promising of which are uterine artery Doppler and biochemistry. We discuss some of the factors to consider when stratifying the obstetric population into degrees of likelihood for growth restriction, and discuss aspects of the management and outcome of pregnancies complicated by growth restriction.

Management of women who use drugs during pregnancy

Substance abuse in pregnancy is associated with significant maternal and fetal morbidity. The complication for care is that the mother is the cause of the problem that potentially harms not only herself but also her unborn child. The abuse is further complicated by the associated legal, social and environmental problems. The aim for the obstetrician is to provide a non-judgemental, supportive environment to minimise the risk, not only during pregnancy and the neonatal period, but also in the long term. To achieve this, caregivers need to be multidisciplinary and tolerant of the mother's problem. The aim of antenatal care is to reduce risk, which does not mean that the mother must abstain from drug use. The aim is to keep her within the care system and encourage her to take responsibility for her situation. No-one should be turned away or denied help as, ultimately, this is harmful to the mother and her baby. To provide this care, the obstetrician needs support from midwives, addiction counsellors, social workers, neonatologists, health visitors and general practitioners. Whereas the healthcare structure in the UK lends itself to this approach, this is not the case in other parts of the world. However, programmes of comprehensive antenatal care do not universally improve the health of the mother and the outcome of her pregnancy. The specifics of the care provided are probably less important than the quality of the care given and the degree of engagement of the individual. This chapter outlines the problems and potential solutions with reference to the service in Leeds in the UK.

Maternal periodontal disease in early pregnancy and risk for a small-for-gestational-age infant

OBJECTIVE

The objective of the study was to determine whether periodontal disease is associated with delivery of a small-for-gestational-age infant.

STUDY DESIGN

In a prospective study of oral health, periodontal disease was categorized as health, mild, or moderate/severe on the basis of clinical criteria. Small for gestational age was defined as birth weight less than the 10th percentile for gestational age. A risk ratio (95th percentile confidence interval) for a small-for-gestational-age infant among women with moderate or severe periodontal disease was calculated.

RESULTS

Sixty-seven of 1017 women (6.6%) delivered a small-for-gestational-age infant, and 143 (14.3%) had moderate or severe periodontal disease. The small-for-gestational-age rate was higher among women with moderate or severe periodontal disease, compared with those with health or mild disease (13.8% versus 3.2% versus 6.5%, P < .001). Moderate or severe periodontal disease was associated with a small-for-gestational-age infant, a risk ratio of 2.3 (1.1 to 4.7), adjusted for age, smoking, drugs, marital and insurance status, and pre-eclampsia.

CONCLUSION

Moderate or severe periodontal disease early in pregnancy is associated with delivery of a small-for-gestational-age infant. Understanding the mechanism of periodontal disease-associated adverse pregnancy outcomes could lead to interventions to improve fetal growth.

Anesthesia and acoustic stress-induced intra-uterine growth retardation in mice

Stress interferes with reproduction, adversely influencing implantation and fetal growth, and sometimes even leading to abortion. Here, we attempted to evaluate the early gestational effects of uncomfortable sound on pregnant mice and their offspring. Ten-week-old pregnant Jcl:ICR mice were exposed to sound (100 dB, random frequency between 9-34 kHz) for 8 hours on the 3(rd), 5(th) and 7(th) gestational days (GD). The effects of general anesthesia were also investigated, with or without acoustic stress. All groups were examined on the 18(th) GD for fetal growth. Fetal weight, number of ossified sacrococcygeal vertebrae and placental weight were all significantly reduced (P<0.0001) when stress was induced on the 7(th) GD, but not on the 3(rd) or 5(th) GD. This intra-uterine growth retardation (IUGR) was significantly inhibited by general anesthesia (P<0.0001), although general anesthesia alone induced significant IUGR (P<0.0001) when compared with control mice. This suggests that acoustic exposure indirectly exerts an effect on fetal growth, possibly via a psycho-maternal pathway. We also found that analysis of the number of ossified sacrococcygeal vertebrae is the most sensitive tool for the study of IUGR.

A review of the literature relating caffeine consumption by women to their risk of reproductive hazards

From this detailed review of the literature, several conclusions can be drawn: (a) An association between caffeine consumption and a reproductive hazard is more likely to be seen in lower-quality studies than in studies that come closer to approximating the ideal. This is especially evident for "lower" birthweight and congenital anomalies. (b) The association between caffeine consumption and spontaneous abortion may well reflect the Stein-Susser epiphenomenon (women with prominent nausea tend to reduce caffeine consumption and nausea appears to be a marker of good implantation, perhaps reflecting a favorable balance of hormones produced by a healthy placenta). (c) The claim that caffeine consumption by women delays conception has not been followed by convincing support. (d) Reproductive hazards associated with cigarette smoking tend to be associated with caffeine/coffee consumption. Sometimes this appears to be a consequence of residual confounding associated with inadequate adjustment for cigarette smoking, which is over-represented among those who drink the most coffee/caffeine. Sometimes this reflects the tendency of women to underreport socially undesirable behaviors (e.g. smoking) while accurately reporting socially neutral behaviors (e.g. coffee and caffeine consumption). Thus, it seems reasonable to conclude that no convincing evidence has been presented to show that caffeine consumption increases the risk of any reproductive adversity.

Drugs of abuse in pregnancy

Care for the drug-using pregnant woman is being increasingly recognized as part of the obstetrician's role. There is great potential for improvement in provision of services for this group of women, partly because traditionally our antenatal clinics have not been perceived as being conducive to disclosure regarding drug use, but also because hard data and, indeed, randomized controlled trials on the subject, are scarce.From the little evidence available, and from our own experience in this area, we have attempted to outline the main problems encountered in the antenatal, intrapartum and postnatal periods with each of the main drugs of abuse and the management thereof. It is important to note that we include cigarette smoking and alcohol, probably the most commonly used drugs in pregnancy, and recognize that the picture is wider than the stereotypical emaciated intravenous heroin addict. Where possible, evidence from trial data is included, but much of the what is quoted is descriptive from personal experience from ourselves and others working in the field.

Induced abortion and low birthweight in the following pregnancy

BACKGROUND

To examine whether induced abortion increases the risk of low birthweight in subsequent singleton live births.

METHODS

Cohort study using the Danish Medical Birth Registry (MBR), the Hospital Discharge Registry (HDR), and the Induced Abortion Registry (IAR). All women who had their first pregnancy during 1980-1982 were identified in the MBR, the HDR, and the IAR. We included all 15,727 women whose pregnancy was terminated by a first trimester induced abortion in the induced abortion cohort and 46,026 women whose pregnancy was not terminated by an induced abortion were selected for the control cohort. All subsequent pregnancies until 1994 were identified by register record linkage.

RESULTS

Low birthweight (<2500 g) in singleton term live births occurred more frequently in women with one, two, three or more previous induced abortions, compared with women without any previous induced abortion of similar gravidity, 2.2% versus 1.5%, 2.4% versus 1.7%, and 1.8% versus 1.6%, respectively. Adjusting for maternal age and residence at time of pregnancy, interpregnancy interval, gender of newborn, number of previous spontaneous abortions and number of previous low birthweight infants (control cohort only), the odds ratios (OR) of low birthweight in singleton term live births in women with one, two or more previous first trimester induced abortions were 1.9 (95% CI: 1.6, 2.3), and 1.9 (95% CI: 1.3, 2.7), respectively, compared with the control cohort of similar gravidity. High risks were mainly seen in women with an interpregnancy interval of more than 6 months.

CONCLUSIONS

The findings suggest a positive association between one or more first trimester induced abortions and the risk of low birthweight in subsequent singleton term live births when the interpregnancy interval is longer than 6 months. This result was unexpected and confounding cannot be ruled out.

Adverse pregnancy outcome in schizophrenic women: occurrence and risk factors

Low birth weight and preterm birth are important predictors of infant mortality and morbidity, and may increase the risk of schizophrenia. These adverse outcomes of pregnancy could be associated, therefore, with increased risk in children genetically predisposed to schizophrenia. The aim of this review was to describe the occurrence of risk factors for low birth weight, preterm birth, and perinatal death among schizophrenic women, and to describe the incidence of those adverse pregnancy outcomes among schizophrenic women. Smoking, substance abuse, and low socioeconomic status are associated with fetal growth retardation, preterm birth, and perinatal death, and also with schizophrenia. Therefore, increased incidence of adverse pregnancy outcome should be expected in schizophrenic women. The available evidence suggests that schizophrenic women are at increased risk of delivering infants with low birth weight, but the existing studies are of small statistical power. Preterm birth and perinatal death have only been investigated little among schizophrenic women. An important focus of future research should be to establish the risk of adverse pregnancy outcome, and to study the association between the suspected risk factors and pregnancy outcome in schizophrenic women. In clinical work with pregnant schizophrenic women, efforts should be made to prevent exposure to suspected risk factors like smoking, substance use, and socioeconomic problems. This could possibly decrease the mortality and morbidity, including the risk of schizophrenia in the offspring, and clarify the importance of environmental and genetic factors in the etiology of schizophrenia.

Aetiology and classification of small for gestational age infants

OBJECTIVE

To determine important aetiological factors in small gestational age (SGA) infants and the effectiveness of anthropometric indexes in identifying patterns of growth retardation.

METHODOLOGY

Eighty-four SGA infants and 81 controls were enrolled. Maternal biological, lifestyle and psychosocial factors were compared for the total group and the term Caucasian subset. Anthropometric indexes were also examined in relation to growth patterns.

RESULTS

Decreased maternal size, poor weight gain, previous SGA infant and smoking were significantly associated with SGA status. Poor parental education and unemployment was increased in the study group. Mothers of SGA infants, especially the term Caucasian group, had a greater prevalence of hypertension and depressive and stress symptomatology. Ponderal index failed to identify discreet patterns of disproportionate/proportionate growth retardation.

CONCLUSION

Biological, lifestyle and psychosocial differences remain important aetiological factors of intrauterine growth retardation. Identification of specific patterns of growth retardation by ponderal index remains controversial.