Exposure of young infants to environmental tobacco smoke: breast-feeding among smoking mothers

OBJECTIVES: This study examined the degree to which breast-feeding and cigarette smoking by mothers and smoking by other household members contribute to the exposure of infants to the products of tobacco smoke. METHODS: The subjects were 330 mother-infant pairs derived from a cohort of 1000 pairs enrolled in a longitudinal study of the pulmonary effects of prenatal and postnatal smoking. The main outcome measure was corrected urinary cotinine levels. RESULTS: Urinary cotinine levels were 10-fold higher in breast-fed infants of smoking mothers than among bottle-fed infants of smoking mothers. Among infants of nonsmoking mothers, urine cotinine levels were significantly increased in infants living in homes with other smokers; in this group there was no significant difference between bottle-fed and breast-fed infants. Infants whose mothers smoked in the same room as the infant had only nonsignificant increases in cotinine levels compared with infants whose mothers restricted their smoking to other rooms. CONCLUSIONS: Breast-fed infants of smoking mothers have urine cotinine levels 10-fold higher than bottle-fed infants whose mothers smoke, suggesting that breast-feeding, rather than direct inhalation of environmental tobacco smoke, is the primary determinant of cotinine levels in infants whose mothers smoke.     

Smoking during pregnancy measured by population cotinine testing

AIM: To establish a baseline cross-sectional prevalence of maternal smoking, measured by antenatal serum cotinine testing, in a population of pregnant women. METHODS: Residual sera from first and second routine antenatal blood samples were collected anonymously over a six-month period for pregnancies within the Canterbury region. Cotinine levels were measured by an ELISA test with a result of > 14 ng/mL indicative of active smoking. Only pregnancies ending in a confirmed live birth were considered in smoking prevalence calculations. There was a total of 1948 eligible residual blood samples. RESULTS: Of the 414 residual blood samples available for the first two months of pregnancy, 146 (35.3%) were found to be positive for cotinine. Smoking prevalence decreased over pregnancy so that by the third trimester 225 (26.8%) of 838 samples were cotinine positive. Infants born from smoking mothers had significantly lower birth weights. CONCLUSIONS: In 1994, a third of women tested in early pregnancy and a quarter of women tested in late pregnancy were identified as being smokers. Repeated objective cross-sectional surveys will allow accurate assessment of the efficacy of smokefree interventions both before and during pregnancy.     

A novel thermostable nitrile hydratase

Adverse effects of maternal smoking have been mostly identified through epidemiologic investigations that have used questionnaires to assess active and passive smoking. However, unvalidated self-reports of cigarette smoking may bias true estimates of relative risk of smoking-related health outcomes. This report is based on two separate investigations. First, within a molecular epidemiologic study of the relationship between environmental exposures (smoking, air pollution, diet) and developmental impairment, we have compared self-reported tobacco smoke exposure during pregnancy to plasma cotinine measurements in mothers. One hundred and fifty-eight patients from obstetrical wards in Cracow and in Limanowa, Poland were included in the parent study. Biochemically-identified smokers were defined as persons with plasma cotinine levels greater than 25 ng/mL. The data showed that exposure classification based on self-reported smoking status compared with cotinine values was of low sensitivity (52%) but of high specificity (98%). We assessed the effect of this exposure classification error on the association between low birth weight (LBW) and smoking in pregnancy using data from a related epidemiologic study of children's health in Cracow involving 1115 subjects. The odds ratio (OR) estimates for smoking and LBW after adjustment for exposure misclassification error were significantly higher than before adjustment (crude OR = 2.9, corrected OR = 5.1). The estimated attributable fraction (AF(pop)) based on the crude OR amounted to 22%; however, after adjustment it reached 50%. The corresponding values for the attributable fraction in the exposed group (AF(exp)) were 66% and 80%. These results illustrate the value of validating questionnaire responses on smoking during pregnancy against reliable biologic markers.     

Maternal nutrition and socio-economic status as determinants of birthweight in chronically malnourished African women

The birthweight is the most important determinant of mortality and morbidity in the neonatal period and may have an influence on health in adult life. The high rate of low birthweight in developing countries is therefore a major health problem. Maternal malnutrition is usually assumed to be a causal factor but other environmental factors are also involved. In this study we analysed maternal nutritional and socio-economic factors as determinants of birthweight in term infants from a rural African society characterised by a high rate of chronic malnutrition. Relations of maternal weight, gestational weight gain, parity, socio-economic status and infant sex with birthweight were analysed in 1,477 women and child pairs. The selected women were followed from early pregnancy and had an uncomplicated delivery at term of a living singleton child. The gestational weight gain was 5.6 (SD 6.0) kg and the mean birthweight 2.933 kg (SD 408). Maternal weight, representing the maternal long-term nutritional situation, was the most important independent determinant of birthweight, accounting for 13.0% of the variance in birthweight. The weight gain, representing the short-term nutritional situation, explained only 5.6% of the variance. Birthweight increased by 20 g (CI 18-23) for each kg maternal weight and by 15 g (CI 12-18) for each kg gestational weight gained. The socio-economic difference in birth-weight was 153 g (CI 109-196) 88 of which (CI 48-128) remained unexplained after adjustment for differences in maternal weight, parity and gender. Improved long-term nutritional situation and living conditions seems to be the most important prerequisites to counteract low birthweight in developing countries.     

Oncogenic ras induces gastrin gene expression in colon cancer

BACKGROUND: Exposure to environmental tobacco smoke is associated with detrimental effects on pulmonary function in children. The authors investigated the relation between airway complications in children receiving general anesthesia and the passive inhalation of tobacco smoke. METHODS: Six hundred two children scheduled to receive general anesthesia were enrolled in this prospective study. The anesthesiologist and the recovery room nurse, unaware of the smoke exposure history, recorded the occurrence of airway complications. A history of passive smoking was assessed by measuring the urinary concentration of the major nicotine metabolite cotinine and by questionnaire. RESULTS: Airway complications occurred in 42% of the patients with urinary concentrations of cotinine > or =40 ng/ml, in 33% of the patients with concentrations of cotinine between 10.0 and 39.9 ng/ml, and in 24% of the patients with concentrations of cotinine < 10 ng/ml (P = 0.01 for the trend among the three groups). The gender of the child (P = 0.001) and the educational level of the child's mother (P = 0.0008) significantly modified the effect of the concentration of cotinine on the incidence of adverse respiratory events. CONCLUSIONS: There is a strong association between passive inhalation of tobacco smoke and airway complications in children receiving general anesthesia. The relationship is greatest for girls and for those whose mothers have a lower level of education. Passive smoking should be regarded as a risk factor in children undergoing general anesthesia.     

Risk factors for aboriginal low birthweight, intrauterine growth retardation and preterm birth in the Darwin Health Region

Risk factors for Aboriginal low birthweight (< 2500 g), preterm birth (< 37 weeks' gestation) and intrauterine growth retardation (under the tenth percentile of Australian birthweights for gestational age) were examined in 503 live-born singletons recorded as born to an Aboriginal mother and routinely delivered at the Royal Darwin Hospital between January 1987 and March 1990. Infants born to mothers with body mass index less than 18.5 kg/m2 had five times the risk of having low birthweight and 2.5 times the risk of intrauterine growth retardation. Population-attributable risk percentages suggest that 28 per cent of low birthweight and 15 per cent of growth retardation could be attributed to maternal malnutrition. Risk percentages for maternal smoking of more than half a packet of cigarettes a day were 18 per cent for low birthweight and 10 per cent for growth retardation. For growth retardation, 18 per cent could be attributed to a maternal age under 20 years. Risk factors for preterm birth were predominantly obstetric: the population-attributable risk percentage for pregnancy-induced hypertension was 26 per cent and for other obstetric conditions was 16 per cent. For Aboriginal births in the Darwin Health Region, maternal malnutrition and smoking are key elements in the prevention of low birthweight and intrauterine growth retardation. Teenage pregnancy is an important risk for intrauterine growth retardation, and pregnancy-induced hypertension is a risk for preterm birth.     

Parental smoking and respiratory illnesses in Australian children aged 0-4 years: ABS 1989-90 National Health Survey results

OBJECTIVE: This study investigated the associations between parental smoking and respiratory infections in Australian children aged 0-4 years. METHODS: Data from the ABS 1989-90 National Health Survey were used. The exposure variables examined were maternal, paternal and combined family smoking. Outcome variables were parent-reported chronic or recent asthma, asthma wheeze, bronchitis, influenza, common cold, cough, otitis media and other respiratory conditions. Logistic regression techniques were used to control for confounding by socio-economic status, child's sex, maternal education, place of residence, ethnicity and family size. RESULTS: Of the 4,281 children in the sample, 45% lived in households with one or more current smokers and 29% had a mother who smoked. Maternal (but not paternal) smoking was significantly associated with asthma (OR 1.52, 95% CI 1.19-1.94) and asthma wheeze (OR 1.51, 95% CI 1.26-1.80). No other significant associations were observed. Positive and significant dose response relationships were found between the amount of maternal smoking and both asthma variables. Population attributable risks were calculated and almost 13% of asthma and asthma wheeze in 0-4 year old Australian children in 1989-90 was estimated to be due to maternal smoking. CONCLUSION: Large numbers of Australian children live in households with smokers. This study, like others, has shown an association between maternal smoking and respiratory illnesses in young children. Further strategies are needed to prevent or reduce young children's exposure to environmental tobacco smoke in their homes.     

Concentration of metals, ceruloplasmin, metallothionein and the activity of N-acetyl-beta-D-glucosaminidase and gamma-glutamyltransferase in pregnant women who smoke and in those environmentally exposed to tobacco smoke and in their infants. Part I

Concentrations of metals (Zn, Cu, Se, Cd), metallotionein (MT) and ceruloplasmin (Cp), and the activity of N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutamyltransferase (gammaGT) in pregnant women who smoke and in passive smokers as well as in their newborns were measured. In smoking women a many-fold increase in cotinine concentrations in maternal and infant urine, amniotic fluid, placenta and milk was found as compared to passive smokers. Smoking lowered serum Se concentration in mothers and infants, increased serum ceruloplasmin in mothers and decreased serum Cu concentration in infants. Serum Zn level in infants was higher than in mothers, and smoking furthered its increase. Statistically significant increase in concentrations of Cd in placenta, amniotic fluid and milk, of Cu in placentae and amniotic fluid and of Zn in placenta and milk was revealed. Higher concentrations of metals were accompanied by an elevated MT level in placenta and amniotic fluid. In smoking women a significant increase in NAG activity in urine, amniotic fluid and milk, increase in gammaGT activity in urine and amniotic fluid and decrease in gammaGT activity in milk and placenta were observed. There was high, positive correlation between MT/NAG and MT/gammaGT in amniotic fluid of passive and active smokers, while similar correlation in milk was indicated only in the group of active smokers. The biochemical parameters analysed proved their usefulness in the evaluation of effects of exposure to cigarette smoke on pregnant woman and her fetus.     

Risk factors for low birth weight and intrauterine growth retardation in Santiago, Chile

An epidemiologic case-control study to ascertain the determinants of low birthweight was carried out in Santiago, Chile, from January to December 1989. The cases were defined as livebirths < 2500 g. The controls were livebirths > or = 2500 g of birthweight. All cases and a random sample (1:1) of controls were selected among 8,254 singleton births occurring at the El Salvador Hospital in the Eastern area of Santiago. These deliveries represented 50% of institutional deliveries in the area. Home deliveries (2%) and private hospital deliveries were not included in the study. Information was obtained from hospital medical records by six trained medical students. Some information could not be obtained from the hospital medical records. Thus the second step in data collection was the tracking of all the selected subjects to their referring neighborhood health centers. For the analysis, the data were divided into 3 case (outcome) categories: 453 subjects were the total case group. From these, 153 were the IUGR case group and 300 were the LBW preterm case group. The general control group consisted of 605 normal birthweight infants. 565 were the IUGR control group and 40 were the preterm control group. A total of 25 risk factors showed a significant crude odds ratio for at least one of the groups. In the multivariate logistic regression analysis eight variables: No. of pregnancies, previous adverse outcomes, previous LBW, pregnancy maternal weight, No. of visits, month of first prenatal care visit, maternal smoking and intrahepatic cholestasis of pregnancy, were significantly associated with LBW after adjustment by confounding. Eight risk factors: IUGR in previous pregnancies, Previous adverse outcome, Maternal smoking, intrahepatic cholestasis, maternal pregnancy weight, maternal height, month first prenatal visit, No. of visit, were significant to IUGR. Only two variables: pregnancy weight, divorced mother, were significantly associated with low birth weight in the preterm group. The most relevant risk factors were included in stepwise logistic regression models carried out for the outcome LBW for the general group, term group and preterm group, in order to adjust by confounding. Adjusted odds ratios were then obtained. Prenatal care related factors and maternal adverse obstetric factors were at higher significance for LBW in the general and IUGR groups. Only nutritional factors were related to LBW in preterm group. Women who delivered a LBW or IUGR infant were more likely to have fewer pregnancies, a history of previous LBW, lower prepregnancy weight and lower gestational weight gain. ICP was associated with an elevated risk of LBW that was independent of gestational age.     

Relationship of prenatal cocaine exposure and maternal postpartum psychological distress to child developmental outcome

Maternal cocaine use during pregnancy can affect the infant directly through toxic effects or indirectly through cocaine's influence on maternal psychological status. We followed 160 cocaine exposed and 56 nonexposed infants and their mothers identified at birth through interview and/or urine screen. Although cocaine exposure defined the groups, infant exposure to alcohol, marijuana, and tobacco was allowed to vary. Infants were 99% African American and poor. All mothers completed the Brief Symptom Inventory (BSI) and infants were given the Bayley Scales of Mental (MDI) and Motor (PDI) Development at a mean corrected age of 17 +/- 8 months. Both MDIs (94 +/- 17 vs. 103 +/- 16) and PDIs (101 +/- 16 vs. 108 +/- 12) were lower for cocaine exposed infants. Psychological distress was greater in cocaine using mothers. Hierarchical multiple regression was used to assess the relative effects of gestational age, maternal psychological distress, and cocaine and polydrug exposure on infant outcomes. Both psychological distress and cocaine and alcohol exposure predicted lower MDIs after controlling for prematurity. Neither psychological distress nor alcohol exposure predicted motor outcome, while cocaine had a significant effect. Tobacco and marijuana exposure were unrelated to outcome. These findings provide further support for direct effects of cocaine and alcohol on infant development as well as highlight the need for studies to document maternal psychological factors, which may increase child risk for poorer outcomes.     

Thinness at birth in a northern industrial town

OBJECTIVE: To determine whether babies in an area of Britain with unusually high perinatal mortality have different patterns of fetal growth to those born elsewhere in the country. DESIGN: Measurement of body size in newborn babies. SETTING: Burnley (perinatal mortality in 1988 15.9/1000 total births) and Salisbury (perinatal mortality 10.8/1000 total births), England. SUBJECTS: Subjects comprised 1544 babies born in Burnley, Pendle, and Rossendale Health District, and 1025 babies born in Salisbury Health District. MAIN OUTCOME MEASURES: Birthweight, length, head, arm and abdominal circumferences, and placental weight were determined. RESULTS: Compared with babies born in Salisbury, Burnley babies had lower mean birthweight (difference 116 g, 95% confidence interval (CI) 77,154), smaller head circumferences (difference 0.3 cm, 95% CI 0.2, 0.4), and were thinner as measured by arm circumference (difference 0.3 cm, 95% CI 0.3, 0.4), abdominal circumference (difference 0.5 cm, 95% CI 0.4, 0.6) and ponderal index (difference 0.8 kg/m3, 95% CI 0.6, 1.0). The ratio of placental weight to birthweight was higher in Burnley (difference 0.6%, 95% CI 0.4, 0.9). These differences were found in boys and girls and did not depend on differences in duration of gestation or on the different ethnic mix of the two districts. Mothers in Burnley were younger, shorter in stature, had had more children, were of lower social class, and more of them smoked during pregnancy than mothers in Salisbury. These differences did not explain the greater thinness of their babies. CONCLUSIONS: Babies born in Burnley, an area with high perinatal mortality, are thin. The reason is unknown. Poor maternal nutrition is suspected because Burnley babies have a higher ratio of placental weight to birthweight. The greater thinness at birth of Burnley babies could have long term consequences, including higher rates of cardiovascular disease.     

Idiopathic normal pressure hydrocephalus: analysis of factors related to cerebrospinal fluid dynamics determining functional prognosis

OBJECTIVE: To examine the effect of maternal smoking on the relationship between maternal hemoglobin levels and pregnancy outcome. DESIGN: A prospective study of healthy parous women from early pregnancy and of their infants. SETTING: Three Scandinavian university hospitals covering all deliveries from well defined geographical areas. SUBJECTS: Smoking (669) and non-smoking (368) mothers, para 1 and 2 and with > or = 37 weeks of gestational length. MAIN OUTCOME MEASURES: Birth weight and placental weight. Ponderal Index and Placental Index as measures of possible discordant fetal and placental growth. RESULTS: In non-smoking mothers the hemoglobin levels in the three trimesters had no relation to birth weight. In smoking mothers a significantly lower birth weight was seen with a high hemoglobin level in the third trimester, but hemoglobin levels in early or mid-pregnancy had no association to birth weight. Smoking mothers also had a significantly greater fall in hemoglobin concentration from first to second and third trimester as compared to non-smokers although ferritin levels were similar in smokers and non-smokers, implying similar iron stores. The ratio of placental weight to the weight of the newborn was significantly higher in smokers, but no association was found to different hemoglobin levels. CONCLUSIONS: Fetal growth impairment associated with maternal smoking is even more pronounced in smoking mothers with high hemoglobin levels in late pregnancy. Smoking mothers were also found to have disproportional fetal/placental growth with relatively high placental weights. In non-smoking mothers hemoglobin levels had no relation to birthweight.     

Increased birth weights in the Nordic countries. A growing proportion of neonates weigh more than four kilos

The proportion of children with high birthweights is increasing in Sweden, as in the other Nordic countries. According to the Swedish national birth registry (founded in 1973), the proportion of term (i.e. (37 gestational weeks) offspring of singelton pregnancies, and weighing four kg or more, increased from 16.9 per cent in 1973 to 20.3 per cent in 1995. The respective figures for the first-born subgroup were 12.9 and 15 per cent, the increase in mean birthweight being from 3400 to 3520 g. There was a corresponding increase in head circumference. The risk of delivery-related complications increases with birthweight over four kg, and a higher incidence of major perineal rupture (grade 3 or 4) has been reported, as well as a disturbing increase in the incidence of brachial plexus damage. Findings in recent studies suggest high birthweight to be associated with an increased risk of subsequent morbidity, both in childhood and in adulthood, specifically diabetes type 1, eczema and certain malignancies, particularly breast cancer and prostate cancer. Although the cause of the increasing proportion of large newborns is not known, it may be partly due to weight increase among gravidae. Another possible explanation is reduced maternal smoking, as smoking is less common now than in the 1970s.     

Effects of maternal smoking during pregnancy and a family history of asthma on respiratory function in newborn infants

INTRODUCTION: Infants of mothers who smoke have reduced respiratory function and are more likely to develop wheezing. Little evidence is available on the effect of in-utero cigarette-smoke exposure as opposed to postnatal exposure to environmental tobacco smoke. We used a previously validated non-invasive method to measure the time to peak tidal expiratory flow (tPTEF) as a proportion of expiratory time (tE) in newborn infants soon after birth to examine the effects of a family history of asthma and in-utero cigarette-smoke exposure on the infants' respiratory function. METHODS: We collected respiratory-function data from 500 healthy infants of mothers taking part in the Western Australia Pregnancy Cohort Study. During behaviourally defined quiet sleep, measurements were obtained a median of 58 h (range 26-159) after the infants were born. We used uncalibrated inductance plethysmography. The uncalibrated volume signal was differentiated to flow and used to calculate respiratory rate, total inspiratory time, tE, and tPTEF. Mothers answered questionnaires on demographic, medical, and pregnancy characteristics, including smoking history. Serum cotinine measurements were available to validate self-reported smoking history in a subset of mothers (238). RESULTS: Data suitable for analysis were obtained from 461 infants. In multivariate regression analysis, lower values of tPTEF/tE were independently associated with respiratory rate (beta coefficient per 10 breaths/min 0.018 [SE 0.005], p < 0.01), age (beta coefficient per 10 h -0.008 [0.003], p < 0.01), maternal smoking during pregnancy (> 10 cigarettes daily; beta coefficient -0.049 [0.022], p < 0.05), maternal hypertension during pregnancy (-0.037 [0.015], p < 0.02), and a family history of asthma (-0.028[0.014], p < 0.05). CONCLUSIONS: In-utero smoke exposure, a family history of asthma, and maternal hypertension during pregnancy are associated with reduced respiratory function after birth. We speculate that these factors adversely affect lung development in utero.     

Acute effects of cigarette smoking on fetal cardiovascular and uterine Doppler parameters

The purpose of this study was to assess the effects of smoking one cigarette (nicotine mean 0.63 +/- 0.17 mg) on uterine- and foetal cardiovascular Doppler parameters in healthy pregnant smokers. All pregnancies (n = 16; mean gestational age: 36 +/- 4 weeks) had been uneventful and all foetuses were appropriate for gestational age with normal baseline Doppler parameters and normal foetal outcome (birthweight: 3254 +/- 340 grams). Measurements, performed immediately before and after smoking, included pulsatility index (PI) of umbilical artery (UA), middle cerebral artery (MCA), foetal descending aorta and uterine artery as well as maternal and foetal heart rate. The ratio of UA/MCA PI was used to assess centralisation. Changes in foetal cardiac output were determined by: time-velocity integral times heart rate, at aortic and pulmonary valve level. Foetal heart rate (p < 0.0005, paired t-test) and maternal heart rate (p < 0.05) increased significantly. All other parameters did not change significantly. However, in one additional woman with labile hypertension and increased baseline uterine artery PI (1.9), smoking of one cigarette caused a substantial rise in uterine artery PI to 3.25 ten minutes after smoking. Middle cerebral artery PI decreased from 2.2 to 1.18 with an unchanged cardiac output and umbilical artery PI raising the UA/MCA PI ratio from 0.51 to 0.81, suggesting a brain sparing effect. Smoking of one cigarette raised maternal and foetal heart rate. There was no evidence of other cardiovascular effects or centralisation in healthy foetuses of normal pregnancies, but this might not be true in foetus of pathologic pregnancies.     

Increasing social variation in birth outcomes in the Czech Republic after 1989

OBJECTIVES: This study investigated social variation in birth outcome in the Czech Republic after the political changes of 1989. METHODS: Routinely collected records on singleton live births in 1989, 1990, and 1991 (n = 380,633) and 1994, 1995, and 1996 (n = 286,907) were individually linked to death records. RESULTS: Mean birthweight fell from 3,323 g to 3,292 g (P < .001) between 1989 and 1991 and then increased to 3,353 g by 1996. The gap in mean birthweight between mothers with a primary education and those with a university education, adjusted for age, parity, and sex of infants, widened from 182 g (95% confidence interval [CI] = 169, 19) in 1989 to 256 g (95% CI = 240, 272) in 1996. Similar trends were found for preterm births. Postneonatal mortality declined most among the better educated and the married. The odds ratio for postneonatal death for infants of mothers with a primary (vs university) education, adjusted for birthweight, increased from 1.99 (95% CI = 1.52, 2.60) in 1989 through 1991 to 2.39 (95% CI = 1.55, 3.70) in 1994 through 1995. CONCLUSIONS: Despite general improvement in the indices of fetal growth and infant survival in the most recent years, social variation in birth outcome in the Czech Republic has increased.     

Pre-mRNA processing enhancer (PPE) element increases the expression of an intronless thymidylate synthase gene but does not affect intron-dependent S phase regulation

Maternal smoking during pregnancy causes reduction of fetal breathing movements, an effect attributed to nicotine in fetal blood. Nicotine is metabolized to cotinine which has a long plasma half-life and exhibits slow clearance across membrane barriers. It is also known to activate placental phospholipase-A2-like enzymes, resulting in formation of prostaglandins. Therefore, we studied transport of nicotine in isolated perfused cotyledon of normal human term placenta. The placental cotyledon was perfused with aerated (21% O2, 5% CO2) Krebs-Ringer bicarbonate buffer (pH 7.4, 37 degrees C) containing 2% albumin on both maternal (230 ml, 15 ml/min, 35 mm Hg) and fetal (93 ml, 1.75 ml/min, 70 mm Hg) sides in a closed recirculating system. Nicotine (2 mg) was added to the maternal perfusate; perfusate samples (1 ml) were collected from both sides at regular intervals and analyzed for nicotine and cotinine by high-pressure liquid chromatography. This study gave the following results: (1) In about 60-80 min, 18.6% of the nicotine added to the maternal perfusate was transferred to the fetal perfusate, and the maternal/fetal concentration ratio reached 1.0. These results show rapid placental transfer of nicotine, consistent with its high lipid solubility. (2) Less than 1% is metabolized to cotinine in placenta. The ratio of cotinine concentrations in maternal and fetal perfusates reached 1.0 in about 40 min. These studies were also verified using 14C-nicotine. (3) Maximal reduction in fetal breathing movements occurs at about 30 min, and recovery occurs at 90 min after tobacco smoking by the mother. These observations agree with the rate of placental transfer of nicotine. (4) When nicotine was added on the fetal side, part of it was metabolized to cotinine. However, the maximal concentration of cotinine was twice higher on fetal than on maternal side. These observations suggest that accumulation of cotinine on fetal side may activate prostaglandin formation and trigger spontaneous abortions in pregnant smokers.     

Cord blood erythropoietin in the presence and absence of labor in normal infants

To evaluate erythropoietin (Ep) levels in normal labor and cesarean section we studied the cord serum of 111 term pregnancies, divided into three groups: (i) those born by normal vaginal delivery (n = 69); (ii) those delivered vaginally from mothers who were smokers (n = 20); and (iii) those delivered by elective cesarean section (n = 22). The three groups did not differ in maternal age, gestational age, birthweight, infant sex and Apgar scores. No correlation was found between Ep and hematocrit in all three groups of normal terms studied. Although not statistically significant the lower mean Ep value observed in cesarean section compared with the values obtained from normal deliveries could suggest that the process of labor may be a cause of these differences.     

The work of the American emergency physician

OBJECTIVE: To compare gestational age (GA) calculated from oocyte retrieval and from ultrasound measurements in pregnancies after in vitro fertilization (IVF). DESIGN: In a retrospective study of 253 women with singleton and 84 women with twin pregnancies conceived from IVF, GA calculated from the day of oocyte retrieval was compared with GA calculated in the second trimester of pregnancy from ultrasound measurements of biparietal diameter (BPD) and femur length (FL). RESULTS: For singletons, the mean GA calculated from ultrasound measurements was significantly shorter than the mean GA estimated from the day of oocyte retrieval. The mean difference was 1.9 days (SD 3.3; 95% CI 1.5-2.4) if only BPD was used and 2.1 days (SD 2.1; 95% CI 1.6-2.5) if BPD and FL were combined. For twins, the mean GA calculated from ultrasound measurements was also significantly shorter than the mean GA calculated from the day of oocyte retrieval. The mean difference was 1.4 days (SD 2.7; 95% CI 1.0-1.8) if BPD was used and 1.6 days (SD 2.5; 95% CI 1.2-2.0) if BPD and FL were combined. CONCLUSIONS: In IVF pregnancies, term prediction using ultrasound in the second trimester is reliable and may reduce the number of pregnancies subsequently classified as post-term, thus avoiding unnecessary obstetric interventions.     

Evidence for an association between environmental tobacco smoke exposure and birthweight: a meta-analysis and new data

Because of the strong association of active smoking with fetal growth retardation, increasing interest has focused on whether there is also an association with exposure to environmental tobacco smoke (ETS). We examined this issue in a retrospective study and by conducting a review of the literature and data pooling. In our study, nonsmoking women with singleton livebirths born in 1986-87 (n = 992) provided information on exposure to ETS for 1 h or more per day and paternal smoking. The risk of low birthweight (LBW, < 2500 g) was not increased in infants of ETS-exposed women, but there was a somewhat increased risk for LBW at term (adjusted odds ratio [OR] 1.8, 95% confidence interval [CI] 0.6, 4.8) and small-for-gestational-age (< 10th percentile of weight; OR = 1.4, 95% CI = 0.8, 2.5). These results were in the range of 16 other studies in the literature that had odds ratios from 1.0 to 2.2. A weighted average of the results of all studies on LBW at term or small-for-gestational-age yielded a pooled estimate of 1.2 [95% CI = 1.1, 1.3] in nonsmoking women. The pooled estimate of mean birthweight indicated a decrement of 28 g with ETS exposure of nonsmoking women [95% CI = -41, -16], with a greater decrement (about 40 g) seen among more homogeneous studies.