Smoking during pregnancy and placental weight: a multivariate analysis on 3759 cases

Placental weight and birthweight: the relations with number of daily cigarettes and smoking cessation in pregnancy. A population study

Background

We studied associations of number of daily cigarettes in the first trimester with placental weight and birthweight in women who smoked throughout pregnancy, and in women who stopped smoking after the first trimester.

Methods

We included all women with delivery of a singleton in Norway (n = 698 891) during 1999-2014, by using data from the Medical Birth Registry of Norway. We assessed dose-response associations by applying linear regression with restricted cubic splines.

Results

In total, 12.6% smoked daily in the first trimester, and 3.7% stopped daily smoking. In women who smoked throughout pregnancy, placental weight and birthweight decreased by number of cigarettes; however, above 11-12 cigarettes we estimated no further decrease (Pnon-linearity < 0.001). Maximum decrease in placental weight in smokers compared with non-smokers was 18.2 g [95% confidence interval (CI): 16.6 to 19.7], and for birthweight the maximum decrease was 261.9 g (95% CI: 256.1 to 267.7). In women who stopped smoking, placental weight was higher than in non-smokers and increased by number of cigarettes to a maximum of 16.2 g (95% CI: 9.9 to 22.6). Birthweight was similar in women who stopped smoking and non-smokers, and we found no change by number of cigarettes (Pnon-linearity < 0.001).

Conclusions

In women who smoked throughout pregnancy, placental weight and birthweight decreased non-linearly by number of cigarettes in the first trimester. In women who stopped smoking, placental weight was higher than in non-smokers and increased linearly by number of cigarettes; birthweight was almost similar to that of non-smokers.

Prenatal Exposure to Select Phthalates and Phenols and Associations with Fetal and Placental Weight among Male Births in the EDEN Cohort (France)

BACKGROUND

The placenta performs crucial physiological functions to ensure normal fetal development. Few epidemiological studies investigated placental weight sensitivity to phthalates and phenols.

OBJECTIVE

Our goal was to explore whether maternal exposure to select phthalates and phenols is associated with changes in placental weight at birth and in placental–to–birth weight ratio (PFR).

METHODS

Placental weight and birth weight were available for 473 mother–son pairs in the EDEN (Etude des Déterminants pré et postnatals du développement et de la santé de l'Enfant) cohort for whom 9 phenols (4 parabens, 2 dichlorophenols, triclosan, benzophenone-3, bisphenol A) and 11 phthalate metabolites were measured in spot urine samples collected between weeks 23 and 29 of gestation. We used adjusted Elastic Net penalized regression models (ENET) to select biomarkers associated with placental weight, birth weight and PFR. Unpenalized effect estimates were then obtained by fitting linear regression models simultaneously adjusted for the ENET-selected biomarkers and a priori chosen confounders.

RESULTS

The multipollutant ENET model for placental weight retained four biomarkers: triclosan and monocarboxy-isononyl phthalate (MCNP), which were negatively associated with placental weight, and benzophenone-3 and the sum of parabens, which were positively associated with this outcome. The ENET model for PFR retained two phthalate metabolites [MCNP and monocarboxy-isooctyl phthalate (MCOP)], which were negatively associated with this outcome.

DISCUSSION

The positive association between the sum of parabens and placental weight was consistent with results of a previous study among 49 male births. Our results provide preliminary evidence of possible associations between other compounds such as triclosan, benzophenone-3, MCNP, and MCOP and both placental weight and PFR. These associations were not reported in previous studies and should be seen as hypothesis generating. Studies relying on repeated assessments of exposure in prospective mother–child cohorts are needed to substantiate the plausibility of the hypotheses generated by our results. https://doi.org/10.1289/EHP3523.

Does multiple gestation impact birthweight deficit from smoking?

OBJECTIVE

To test the hypothesis that the combined birthweight deficit from smoking in twin gestation is significantly greater than previously described for singletons.

STUDY DESIGN

Retrospective cohort study of White/Black live-born twins, 32 to 40 weeks of gestation, 1990 to 2005, Kansas City, MO. Data were analyzed by t-test, χ(2), linear and linear regression analyses.

RESULT

The cohort comprised 1190 twin pairs, 58% Whites and 55% ≥37 weeks. Smoking rate was 14.5% and similar by race (14.2% White vs 14.8%, P=0.772). The aggregate birthweight of twins of nonsmokers was greater, 5116 g ± 25 g vs 4870 g ± 59 g, P<0.001 (mean±s.d.) and the difference was 264 g (95% confidence interval, 156 to 372 g) after adjusting for other variables in linear regression analyses.

CONCLUSION

Smoking-associated growth restriction in twins is quantitatively similar to that of singletons. This finding is suggestive of dissipation or a ceiling effect to the growth-restricting effect of cigarette smoking.

Is the association of maternal smoking and pregnancy-induced hypertension dependent on fetal growth?

OBJECTIVE

The risk of pregnancy-induced hypertension (PIH) is decreased by smoking, but the mechanisms remain unclear. Our objective was to determine whether this association is dependent on decreased fetal growth.

METHODS

A population-based, retrospective cohort study in the United States was performed consisting of nulliparous women who delivered a singleton birth (n = 8,025,295) between 1995 and 2002. Fetal growth was defined as birthweight for gestational age and characterized as less than 1, 1-2, 3-4, 5-9, 10-19, ..., 90 or greater centiles. Risk and relative risk of PIH before and after adjusting for confounders were estimated.

RESULTS

Smoking was associated with decreased risk of PIH with up to a 46% decreased risk of PIH for growth-restricted babies (less than the 10th centile). This association, however, decreased with increasing birthweight centile and was nonsignificant at 20th or greater centile among heavy smokers, at 60th or greater centile for moderate, and 80th or greater centile for light smokers.

CONCLUSION

Smoking was primarily associated with decreased risk of PIH among growth-restricted babies.

Risks and benefits of nicotine to aid smoking cessation in pregnancy

Cigarette smoking during pregnancy is the single largest modifiable risk for pregnancy-related morbidity and mortality in the US. Addiction to nicotine prevents many pregnant women who wish to quit smoking from doing so. The safety and efficacy of nicotine replacement therapy (NRT) for smoking cessation during pregnancy have not been well studied. Nicotine is classified by the US Food and Drug Administration as a Pregnancy Category D drug. Animal studies indicate that nicotine adversely affects the developing fetal CNS, and nicotine effects on the brain may be involved in the pathophysiology of sudden infant death syndrome (SIDS). It has been assumed that the cardiovascular effects of nicotine resulting in reduced blood flow to the placenta (uteroplacental insufficiency) is the predominant mechanism of the reproductive toxicity of cigarette smoking during pregnancy. Short term high doses of nicotine in pregnant animals do adversely affect the maternal and fetal cardiovascular systems. However, studies of the acute effects of NRT in pregnant humans indicate that nicotine alone has minimal effects upon the maternal and fetal cardiovascular systems. Cigarette smoking delivers thousands of chemicals, some of which are well documented reproductive toxins (e.g. carbon monoxide and lead). A myriad of cellular and molecular biological abnormalities have been documented in placentas, fetuses, and newborns of pregnant women who smoke. The cumulative abnormalities produced by the various toxins in cigarette smoke are probably responsible for the numerous adverse reproductive outcomes associated with smoking. It is doubtful that the reproductive toxicity of cigarette smoking is primarily related to nicotine. We recommend the following. Efficacy trials of NRT as adjunctive therapy for smoking cessation during pregnancy should be conducted. The initial dose of nicotine in NRT should be similar to the dose of nicotine that the pregnant woman received from smoking. Intermittent-use formulations of NRT (gum, spray, inhaler) are preferred because the total dose of nicotine delivered to the fetus will be less than with continuous-use formulations (transdermal patch). A national registry for NRT use during pregnancy should be created to prospectively collect obstetrical outcome data from NRT efficacy trials and from individual use. The goal of this registry would be to determine the safety of NRT use during pregnancy, especially with respect to uncommon outcomes such as placental abruption. Finally, our review of the data indicate that minimal amounts of nicotine are excreted into breast milk and that NRT can be safely used by breast-feeding mothers.

Effect of prenatal alcohol and cigarette exposure on two- and six-month-old infants' adrenocortical reactivity to stress

Examined the effect of prenatal alcohol and cigarette exposure on infant adrenocortical reactivity to stress at 2 and 6 months of age. Cortisol response (pre- to poststressor increase) at 2 months was lower for the exposed than nonexposed infants, whereas cortisol response at 6 months did not differ between the exposed and nonexposed infants. The 2-month group difference in cortisol response reflected a higher prestressor cortisol level in the exposed infants.

Smoking during pregnancy: the dose dependence of birthweight deficits

OBJECTIVE

To assess whether a simple urine based estimate of relative daily nicotine intake could predict smoking related birthweight deficits more accurately than self-reported cigarette consumption.

DESIGN

Active smokers were identified by a simple qualitative colorimetric urine test procedure and their relative nicotine intakes assessed by determining the ratios of the urinary concentrations of nicotine plus its metabolites to creatinine using automated colorimetric methods.

SETTING

A large teaching hospital.

PARTICIPANTS

Three thousand and thirty-eight mothers from whom smoking histories had been elicited and who gave birth to live singleton babies after 28 weeks of gestation.

MAIN OUTCOME MEASURES

Birthweights (adjusted for maternal weight, maternal age, baby's sex, parity and length of gestation), maternal weight gains during pregnancy and placental weights.

RESULTS

The adjusted birthweight deficits of babies born to proven active smokers averaged 226 g (95% confidence interval 194 g to 258 g), but dose dependent effects were only apparent when nicotine intake was based on urinary nicotine metabolites/creatinine ratios. Among the smokers, adjusted birthweights fell linearly with increasing nicotine intakes but gave a predicted mean birthweight for nonsmokers that was 102 g (95% CI 50 g to 154 g) lighter than that actually found (P < 0.0001). Maternal weight gains during pregnancy were substantially reduced in smokers and correlated more closely with urinary nicotine metabolite excretions than with reported daily cigarette consumptions. Placental weights were unaffected by smoking.

CONCLUSION

There was a closer dose-effect relationship between birthweight deficits and urinary nicotine metabolites/creatinine ratios than with self-reported daily cigarette consumptions. The influence of nicotine exposure on birthweight appears to be biphasic, with one mechanism operating at very low levels of tobacco smoke intake and the other causing seemingly linearly related effects over the whole range of nicotine intakes of active smokers. These findings support recent evidence that passive smoking can cause substantial birthweight deficits.

The influence of maternal haemoglobin and ferritin on mid-pregnancy placental volume

OBJECTIVE

To investigate whether low maternal haemoglobin and ferritin levels are associated with increased placental volume by mid-pregnancy.

DESIGN

Prospective study of women attending hospital for shared antenatal care.

SETTING

A teaching hospital in the south of England.

SUBJECTS

Five hundred and sixty-eight women booking for delivery in the hospital.

MAIN OUTCOME MEASURES

Placental volume measured by ultrasound at 18 weeks gestation.

RESULTS

At 14 weeks gestation 9% of women had haemoglobin levels < or = 11 g/dl and 26% had ferritin levels < 13 micrograms/l. Placental volume at 18 weeks was inversely related to the maternal haemoglobin and ferritin levels. The influence of haemoglobin and ferritin concentrations was independent of maternal social class, parity, smoking, and weight. Larger placentae were found in taller women, those who had previously been pregnant, and in those who were smoking more than 15 cigarettes daily at the time of their last menstrual period.

CONCLUSION

These data suggest that placental development is influenced from early in pregnancy by the intrauterine environment provided by the mother. In conjunction with other studies they support the proposal that, as a result of these changes, programming of adult blood pressure may be initiated in early pregnancy.

Structural changes in placental barrier of smoking mother. A quantitative and ultrastructural study

Human placental villi from all three trimesters of pregnancy, in 90 non-smoking pregnants and 244 cigarette smoking pregnants, were investigated. In smokers, the numbers of syncytial knots and cytotrophoblastic cells increased, depending on the cigarettes per day, syncytial buds and vasculo-syncytial membranes decreased as the pregnancy proceeded. The mean birth weight and placental weight in smokers were decreased, depending on the cigarettes per day at the third trimester. The ultrastructure of placental villi from smokers were compared with that on non-smokers. The villi from smokers had abnormalities of the microvilli, focal syncytial necrosis, decreased syncytial pinocytotic activity, degenerated cytoplasmic organelles. Using a morphometric method, the basement membranes were measured throughout pregnancy. The mean thickness of the basement membranes of trophoblastic layer and fetal capillary were found to not only increase with the maternal smoking during pregnancy but also attain the maximum in the heavy smokers by the third trimester of pregnancy. There was increased collagen in the villous stroma and shrinkage endothelial changes in fetal capillaries, in smokers the deleterious effect of the cigarette smoking on the placental barrier was heavy damage. As a result of impairment of placental barrier, the transports between mother and fetus were hampered.

Cigarette smoking during pregnancy lowers aromatase cytochrome P-450 in the human placenta

To clarify whether cigarette smoking during pregnancy causes an organic alteration in placental estrogen producing ability, we determined the catalytic activity of aromatase by the tritiated water assay, and tissue level of aromatase cytochrome P-450 (P-450arom) by the specific enzyme-linked immunosorbent assay, in placental samples from nonsmokers and smokers. As pregnancy progressed, both aromatase activity and P-450arom concentration increased in placentas from nonsmokers and smokers. However, the gradient of the increase was significantly less in heavy smokers (> or = 20 cigarettes a day) than in normal and moderate smokers (< 20 cigarettes a day). At term, the mean aromatase activity and P-450arom concentration in placentas from heavy smokers were significantly lower than in nonsmokers and moderate smokers, while aromatase activity per P-450arom (turnover rate) and the mean placental weight were comparable among the three groups. In contrast, the ratio of aryl hydrocarbon hydroxylase activity to aromatase activity was higher in placentas from heavy smokers. Immunohistochemical studies showed that P-450arom was localized in the cytoplasm of syncytiotrophoblasts of chorionic villi in placentas from both nonsmokers and smokers. These results suggest that the induction of placental P-450arom during gestation is suppressed by maternal smoking, resulting in a reduction in estrogen producing ability, while placental xenobiotic P-450 is induced.

The relation of fetal length, ponderal index and head circumference to blood pressure and the risk of hypertension in adult life

The blood pressure of 327 men and women aged 46 to 54 years was related to birthweight, placental weight, length, ponderal index and head circumference at birth. All the subjects were born after 38 completed weeks of gestation. There were strong trends of higher blood pressure in adult life with lower birthweight (P = 0.04) and greater placental weight (P = 0.002). In subjects with placental weights of 1.25 lb or less, mean blood pressure, and the risk of hypertension, rose as ponderal index at birth fell (P = 0.0001). Mean systolic pressure rose by 13 mm Hg as ponderal index fell from greater than 14.75 to 12 or less. In those with placental weights above 1.25 lb, mean blood pressure, and the risk of hypertension, rose as length decreased and as the ratio of head circumference to length increased (P = 0.02). Mean systolic pressure rose by 14mm Hg as the head circumference to length ratio increased from less than 0.65 to greater than or equal to 0.7. These findings characterise the birth measurements of two groups of babies who are at increased risk of hypertension in adult life.

Effect of smokeless tobacco on the development of the CD-1 mouse fetus

The objective of this study was to examine the effect of an aqueous extract of smokeless tobacco (ST) on the development of the CD-1 mouse fetus. Three ST dosages were administered three times daily by gastric intubation during gestational days 1-17: 1 X ST equivalent to a dose of 4 mg nicotine/kg body weight, 3 X ST equivalent to 12 mg nicotine, and 5 X ST equivalent to 20 mg nicotine/kg body weight. Maternal plasma nicotine levels were determined 30 minutes after the second daily intubation at five different times during the gestational period. At these ST dosages, the weight gain of ST-treated dams was not significantly affected in comparison to treated controls, though the difference was significant (P less than .05) in comparison to untreated controls. The mean maternal plasma nicotine level for the low dosage (1 X) group was 99.0 ng/ml, which reasonably approximates human consumption levels. The 3 X ST and 5 X ST dosages produced higher nicotine plasma values, 398 ng/ml and 623 ng/ml, respectively, were considerably more toxic to the dams, and resulted in 18% and 31% maternal deaths. Fetal weights were reduced by 7.4% (P less than .001) in the highest ST dosage group (5 X), whereas at the 1 X and 3 X dosages fetal weight differences were not significantly different from treated controls. Resorptions increased in a dose-related manner (P less than .05), ranging from 4.7% in the 1 X, to 6.4% in the 3 X and 8.9% in the 5 X dosage compared to 3.2% in treated controls. External malformations were few and minor in extent. Internal malformations increased in a linear, dose-related manner (P less than .05). Placental weights were unaffected by ST. The results of skeletal examinations were inconclusive. Precocious ossification was seen in 60% and 70% of the parameters measured in the 1 X and 3 X dosage groups, respectively, in comparison to controls. In the 5 X ST group ossification levels were less than in controls for 30% of the parameters measured. Under these experimental conditions the lowest ST dosage (1 X) produced a negligible effect on the CD-1 mouse fetus and the dam. The highest ST dose (5 X) demonstrated embryotoxicity, growth retardation, few malformations, and maternal toxicity. The intermediate dose (3 X) showed a range of effects between the highest and lowest doses to both the fetus and the dam.

Morphometric differences between the placental vasculature of non-smokers, smokers and ex-smokers

The aim of this study was to determine whether cigarette smoking during pregnancy has an adverse effect upon the placenta's capacity for gaseous exchange. Using recently developed stereological techniques, in conjunction with perfusion fixation, computer-assisted measurements were made on the placentas of 15 non-smokers, 15 moderate smokers, 15 heavy smokers and 13 ex-smokers, 7 of whom stopped smoking during the course of the pregnancy. Compared with the placentas of non-smokers and of those who stopped before pregnancy, it was found that the placentas of smokers and of those who stopped after conception exhibited a reduced capillary volume fraction, and an increased thickness of the villous membrane. Although they must impair gaseous exchange across the placenta, these changes were less severe than suggested by previously published reports. Nonetheless it is clear that in order to prevent these changes women should stop smoking before conception rather than during the course of a pregnancy.

Embryopathic risks of cigarette smoking

Cigarette smoking has been associated with infertility, a higher frequency of spontaneous abortions, intrauterine growth retardation and an increased incidence of birth defects. Nicotine is the major pharmacological component of cigarette smoke. Its potential reproductive and teratological risks are critically reviewed.

Effect of smokeless tobacco on the development of the CD-1 mouse fetus

The objective of this study was to examine the effect of smokeless tobacco (ST) on the development of the CD-1 mouse fetus. ST was administered continuously via Alzet osmotic minipumps during the critical gestational days 7-14 and 6-13. Two ST dosages were administered, 3.2 mg/ml (Dosage I) and 6.4 mg/ml (Dosage II), which yielded plasma nicotine levels within the range comparable to those of an average ST user or smoker (36.0 ng/ml). Plasma nicotine levels were maintained in the range of 29.4 +/- 4.8 ng/ml to 44.3 +/- 16.0 ng/ml for the Dosage I group of dams, and in the range of 34.6 +/- 10.9 ng/ml of 75.5 +/- 19.9 ng/ml for the Dosage II group of dams. The main effect on the fetus was weight reduction, with Dosage I producing a tendency toward weight reduction (p = .08). Dosage II produced a significant 8.6% weight reduction from normal (p less than .0001) and an increase in fetal deaths (p less than .03). Dosage I produced an increase in the incidence of hemorrhages and supernumerary ribs, and a significant delay (p less than .05) in ossification of the supraoccipital bone, the sacrococcygeal vertebrae, and the bones of the forefoot and hindfoot. There were no significant differences between placental weights. Weights of dams were significantly reduced only at the higher ST exposure levels. We conclude that at plasma nicotine levels comparable to those of an average ST user, ST produces weight reduction, delayed ossification, and increase in hemorrhages and fetolethality in the CD-1 mouse fetus.

The effects of cigarette smoking on the human placenta: a light and electron microscopic study

A histological and electronoptical study of placentae from women who smoke cigarettes during pregnancy shows a tendency towards a paucity of vasculosyncytial membranes, villous cytotrophoblastic cell proliferation, focal syncytial necrosis, decreased syncytial pinocytotic and secretory activity, dilatation of syncytial rough endoplasmic reticulum, abnormalities of syncytial microvilli, focal infolding of the free plasma membrane of the syncytiotrophoblast, degeneration of isolated cytotrophoblastic cells, irregular thickening of the trophoblastic basement membrane and degeneration of villous capillary endothelial cells. It is thought that many of these changes are due to placental ischaemia consequent upon nicotine-induced constriction of the uterine vessels; some of the changes cannot be explained on this basis and it is suggested that these may possibly be due either to cadmium toxicity or to accumulation of polycyclic aromatic hydrocarbons. There is apparently some impairment of placental function in cigarette smokers but this is probably offset by the ability of the placenta to repair ischaemic damage and to undergo a compensatory hyperplasia.

Smoking in pregnancy and subsequent development of the child

Data from the National Child Development Study have been used to examine the relationship between mother's smoking during pregnancy and neonatal mortality, birthweight and the subsequent development of the child to the age of 11. In this paper analyses are reported which extend this work to examine development by the age of 16. After allowing for a wide range of related background factors, it is found that mothers smoking during pregnancy continues to be related to the child's reading and mathematics attainment. For boys, but not girls, there is an association with height. An inconsistent relationship is found with the child's history of asthma and wheezy bronchitis. Some doubts about the direct causality of such relationships are discussed.