Smoking during pregnancy and preterm birth

Objective To evaluate the association between smoking during pregnancy and preterm birth.
Design A follow up study.
Setting Department of Gynaecology and Obstetrics, Aarhus University Hospital, Denmark.
Participants Four thousand one hundred and eleven nulliparous women with singleton pregnancies who returned questionnaires about smoking habits at 16 weeks of gestation.
Results The overall rate of preterm delivery was 4.3 %. Smokers had a 40 % higher risk of preterm birth compared with nonsmokers. A dose response relationship was found between smoking and risk of preterm birth. Adjustment for women's height, prepregnancy weight, age of the mother, marital status, education, occupational status, and alcohol intake did not change the results. Among women with an intake of less than 400 mg of caffeine per day no difference in the risk of preterm birth between smokers and nonsmokers was found. However, among women with an intake of more than 400 mg of caffeine per day, the risk of preterm birth was increased almost threefold among smokers compared with nonsmokers. Furthermore, among women with a high intake of caffeine a dose-response relationship was found; women smoking one to five cigarettes per day had no increased risk of preterm birth compared with nonsmokers with the same intake of caffeine, women smoking six to ten cigarettes per day had almost three times higher risk of preterm birth, and women smoking more than 10 cigarettes per day had almost five times higher risk of preterm birth compared with nonsmokers with the same intake of caffeine.
Conclusions Smoking increases the risk of preterm birth. The association between smoking and preterm birth was only present among women with a high intake of caffeine. However, whether smoking alone influences the risk of preterm birth among heavy consumers of caffeine needs further investigation.     

Smoking during pregnancy and the perinatal cadmium burden

The association between maternal smoking and both morphometric birth parameters and the perinatal cadmium burden were studied. The cadmium concentrations were measured by atomic absorption spectrometry in 100 samples of maternal whole blood (MB) and in 93 samples of umbilical cord blood (CB). In the group of nonsmokers, significantly higher birth weight and decreased relative placental weight were noted as compared to the group of smokers who smoked more than 6 cigarettes a day (p less than 0.05). In both maternal and cord blood samples, the measured Cd levels were found to be significantly higher in smokers than in the nonsmoking subjects (for MB and CB p less than 0.01 and p less than 0.01 respectively). The average number of cigarettes smoked daily by the women had little effect on the levels of the metal. The Cd-MB strongly correlated with the Cd-CB (p less than 0.001). The cadmium values determined in MB and CB did not significantly affect any of the studied fetoplacental parameters. The reported findings give support for placental permeability to cadmium in humans and confirm that smoking during pregnancy leads to elevated Cd concentrations in both the mother and the fetus.     

Pharmacokinetics during pregnancy: evidence-based maternal dose formulation

Objective: To review the literature regarding how drug pharmacokinetics differ between pregnant and nongravid women.Data Sources: Articles published between 1963 and 1997 were retrieved from the database of the National Library of Medicine for review, using the key words “pregnancy,” “pharmacokinetics,” and “human.” Additional articles and book chapters were identified from the bibliographies of articles retrieved.Methods of Study Selection: Articles had to include primary data that were not previously published. Data abstracted from articles meeting the inclusion criteria included: sample size, estimated gestational age, area under the curve, volume of distribution, maximum plasma concentration, steady-state concentration, half-life, time to maximum plasma concentration, clearance, and data from nonpregnant controls.Tabulation, Integration, and Results: Of more than 1000 articles published, 61 articles and book chapters reported relevant pharmacokinetic data, such as those listed, based on primary data. Only two studies synthesized pharmacokinetic data into guidelines for individualized clinical regimens.Conclusion: Available data regarding the pharmacokinetics of therapeutic regimens during pregnancy do not provide clinically relevant guidelines for the formulation of therapy for individual patients. Pharmacokinetic investigations during pregnancy that produce evidence-based guidelines for treating individual patients were identified as a major area of need. Minimum requirements are recommended for reporting pharmacokinetic studies in obstetrics.     

Committee opinion no. 471: Smoking cessation during pregnancy

Smoking is the one of the most important modifiable causes of poor pregnancy outcomes in the United States, and is associated with maternal, fetal, and infant morbidity and mortality. The physical and psychologic addiction to cigarettes is powerful; however, the compassionate intervention of the obstetrician–gynecologist can be the critical element in prenatal smoking cessation. An office-based protocol that systematically identifies pregnant women who smoke and offers treatment or referral has been proved to increase quit rates. A short counseling session with pregnancy-specific educational materials and a referral to the smokers’ quit line is an effective smoking cessation strategy. The 5A’s is an office-based intervention developed to be used under the guidance of trained practitioners to help pregnant women quit smoking. Knowledge of the use of the 5A’s, health care support systems, and pharmacotherapy add to the techniques providers can use to support perinatal smoking cessation.     

Smoking during pregnancy: a significant cause of neonatal thyroid enlargement

Summary. The influence of maternal smoking during pregnancy on the function and the echographic volume of the neonatal thyroid gland was examined in an area of borderline iodine intake (median maternal urinary iodine: 315 range 79–1558 nmol/l). There was a positive correlation (  P<0.001  ) between cord serum thiocyanate (SCN) concentrations used as an index of maternal smoking and the maternal smoking habits. The thyroid volume/birthweight ratio increased significantly as a function of SCN values (  P<0.005  ): this increase was secondary to a decrease in birthweight as well as to an increase in thyroid volume. There was also a positive correlation between cord serum thyroglobulin (Tg) and SCN levels (  P = 0.001  ). Serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) values remained within the normal range for age in all newborn infants and were not significantly correlated with SCN values. These results show that smoking during pregnancy in areas with borderline iodine intake may be a significant cause of thyroid enlargement in the newborn.     

Smoking during pregnancy: a significant cause of neonatal thyroid enlargement

The influence of maternal smoking during pregnancy on the function and the echographic volume of the neonatal thyroid gland was examined in an area of borderline iodine intake (median maternal urinary iodine: 315 range 79-1558 nmol/l). There was a positive correlation (P less than 0.001) between cord serum thiocyanate (SCN) concentrations used as an index of maternal smoking and the maternal smoking habits. The thyroid volume/birthweight ratio increased significantly as a function of SCN values (P less than 0.005): this increase was secondary to a decrease in birthweight as well as to an increase in thyroid volume. There was also a positive correlation between cord serum thyroglobulin (Tg) and SCN levels (P = 0.001). Serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) values remained within the normal range for age in all newborn infants and were not significantly correlated with SCN values. These results show that smoking during pregnancy in areas with borderline iodine intake may be a significant cause of thyroid enlargement in the newborn.     

Smoking pattern during pregnancy in Hong Kong Chinese

Background: While the prevalence of young female smokers is rising among the Hong Kong Chinese population, data on their smoking pattern during pregnancy are limited.
Aims: To investigate the smoking habit of Hong Kong Chinese women and their partners during pregnancy.
Methods: Postal questionnaires were sent to 479 couples to explore their smoking patterns during pregnancy at one to two years after the index delivery.
Results: Questionnaires were completed by 247 subjects. Among 117 women who were ever-smokers, 26% had stopped smoking before the index pregnancy, while 60% stopped and 14% reduced smoking during the pregnancy. Most women stopped smoking in the first trimester (93%) and prior to the first antenatal visit (79%). Those who used to smoke fewer cigarettes before pregnancy were more likely to stop smoking during pregnancy but women with a history of recreational drug use were more likely to continue smoking during pregnancy. The post-partum smoking relapse rate was 59% in women who had stopped smoking before or during their pregnancy. Only 2.6% of the partners who were ever-smokers stopped smoking before the pregnancy while smoking habits remained unchanged in 52%.
Conclusions: Approximately one-fifth of an unselected sample of Hong Kong mothers had a history of smoking prior to pregnancy. Pregnancy is an opportune time to implement smoking intervention programs for female smokers and their partners with an emphasis on the maintenance of post-partum smoking abstinence.     

Smoking during pregnancy and postpartum among Tunisian women

Objective.?The validity of self-reported smoking in population surveys remains an important question yet to be answered. This has been of particular concern in a situation where there is a strong social pressure against pregnant and postpartum women. An associated question is what would be the value of measuring urinary cotinine concentrations in such surveys to obtain validated smoking data.

Methods.?Cross-sectional analysis of data on self-reported smoking and urinary cotinine among a sample of 398 pregnant women and recently pregnant, mothers of infants under the age of 2 months, who came to the Family Planning Clinic in Tunis urban area for either prenatal or newborn care. We used quantitative colorimetric urine test based on the könig reaction, in which pink-red chromophores formed from nicotine and its metabolites condensation with barbituric acid were extracted into acetate buffer.

Results.?The smoking prevalence among Tunisian pregnant women or mothers of newborn infants was 4%. The validity of self-reported daily smoking was relatively low. Among women reporting no smoking at the interview 16% misreported active smoking. According to urinary cotinine values, the smoking prevalence was 18.8%.

Conclusions.?These results substantiate the unreliability of self-report on smoking status among women in prenatal and postnatal period and have implications in clinical and education practice.     

Smoking during pregnancy and bulimia nervosa in offspring

Because smoking during pregnancy is implicated in influencing appetite and impulse control in offspring, the aim of this study was to establish if it is associated with bulimia nervosa in offspring. Bulimia was identified at age 30 years among 4046 females, born 5-11 April, 1970. After adjustment for potential confounding factors including body mass index (BMI) and maternal psychiatric morbidity, smoking during pregnancy was associated with bulimia in offspring by age 30 years. Compared with non-smoking mothers, the adjusted odds ratios (95% confidence intervals) for bulimia in offspring were 0.74 (0.25-2.21) for those who gave up before pregnancy, 3.04 (1.16-7.95) for giving up during pregnancy and 2.64 (1.47-4.74) for smoking throughout pregnancy. Smoking during pregnancy was not associated with anorexia nervosa in offspring. Neither BMI nor variation between childhood and adult BMI explain the association. If the association of smoking during pregnancy with bulimia in offspring is causal, then it may operate through compromised central nervous system development and its influence on impulse or appetite control. The increased risk associated with mothers who gave up smoking during pregnancy emphasizes the importance of smoking cessation prior to conception.     

Malaria in pregnancy: the difficulties in measuring birthweight

Recommendations for interventions to control malaria in pregnancy are often based on studies using birthweight as the primary endpoint. Differences in birthweight may be attributable partly to methodological difficulties. We performed a structured search of the literature using 'malaria', 'pregnancy' and 'birth weight' as search terms. Of the clinical trials reporting birthweight, only 33% (14/43) gave information about the timing of the measurement and details on the scales used. Seventy seven per cent explained how gestational age was estimated. We propose a standardised method for the measurement and reporting of birthweight in future studies.     

Maternal healthy lifestyle during early pregnancy and offspring birthweight: differences by offspring sex

Purpose: Individual maternal lifestyle factors during pregnancy have been associated with offspring birthweight; however, associations of combined lifestyle factors with birthweight and potential differences by offspring sex have not been examined.

Materials and methods: Participants (N?=?2924) were identified from a pregnancy cohort in Washington state. Lifestyle factors during early pregnancy were dichotomized based on Alternate Healthy Eating Index score ≥62, leisure time physical activity (LTPA)?≥?150?min/week, not smoking during pregnancy and Perceived Stress Scale score ≤3, then combined into a lifestyle score (0–4). Regression models were run overall and stratified by offspring sex, prepregnancy overweight/obese (BMI ≥25?kg/m²) and prepregnancy LTPA.

Results: Overall, 20% of participants had healthy diet, 95% were nonsmokers, 55% had low stress levels, and 66% were physically active. Lifestyle score was not associated with birthweight (β?=?3.3?g; 95% CI: ?14.5, 21.0); however, associations differed by offspring sex (p?=?.009). For each unit increase in lifestyle score, there was a suggested 22.4?g higher birthweight (95% CI: ?2.7, 47.6) among males and 14.6?g lower birthweight (95% CI: ?39.9, 10.7) among females. Prepregnancy BMI and LTPA did not modify associations.

Conclusions: Healthy lifestyle score in early pregnancy may be associated with greater birthweight among male offspring, but lower birthweight among female offspring.     

Smoking during pregnancy: risk for intrauterine growth retardation and persisting microsomia

Smoking during pregnancy is a major risk factor for intrauterine growth retardation. The aim of the Thuringian SGA - (small-for-gestational-age) - study was to evaluate the effects of maternal smoking during pregnancy on birth weight and length as well as postnatal growth dynamics and catch-up growth.Between 1992 and 2002 in all 2 447 liveborn children were assessed with birth weight (GG) <10th percentile and/or birth length (GL) <- 2.0 SDS. A questionnaire was sent to 383 parents of severe SGA children (GG and/or GL <- 2.5 SDS) to report weight and height of the children actually. 108 reports could analysed (mean age 8.0±3.4 years of life).The number of SGA babies in regard to all liveborn children decreased from 14.1% to 9.4% between 1992 and 2002. 14% of SGA babies were born preterm. The mean nicotine abuse was 2 cigarettes per day (range 0-40). 17.6% of the mothers of SGA babies were smoking, whereas in severe SGA 26.9% of smokers was recorded. There is a inverse correlation of nicotine abuse with birth weight (r=- 0.09; p<0.01) or birth length (r=- 0.08; p<0.01). Catch-up growth did not exist in 30.6% of the severe growth restricted children. The risk for short stature in later life was doubled in SGA children.Nicotine abuse during pregnancy is a risk factor for an SGA baby and could have long-lasting effects on growth dynamics during childhood with a lack of catch-up growth.     

Smoking and illicit drug use during pregnancy: impact on neonatal outcome

OBJECTIVE: To examine the effects of maternal substance use on neonatal outcomes in 212 pregnant cocaine/opiate dependent women who delivered while in active drug treatment. STUDY DESIGN: Using urine toxicology data at delivery, subjects were classified drug positive (+TOX) (n = 53) or negative (-TOX) (n = 159). RESULTS: Toxicology status was not associated with maternal or neonatal demographic or drug use variables. +TOX patients were enrolled in the treatment program for a shorter period of time than -TOX (68.3 vs. 91.3 days, p = 0.005). Infant birth weight ratio (IBR) was lower in +TOX women (0.84 vs. 0.90, p = 0.003). +TOX women were twice as likely to have small-for-gestational-age (IBR < 0.85) neonates than were -TOX. Length of stay (LOS) in the neonatal intensive care unit (NICU) was not associated with maternal toxicology but was associated with quantity of tobacco per day (p = 0.0001). NICU neonates with heavily smoking mothers (11+ cigarettes/day) averaged LOS = 9.5 days as compared to light (1-10 cigarettes per day) smokers (LOS = 7.9 days) and nonsmokers (LOS = 5.5 days). CONCLUSION: Maternal drug abstinence is associated with higher IBR. Maternal smoking is related to NICU LOS, even among polydrug-dependent women. These data are clinically and economically important and support the need for smoking cessation interventions in high-risk populations, such as drug-dependent pregnant women.     

Smoking during pregnancy: comparison of self-reports and cotinine levels in 496 women

OBJECTIVE: To validate self-reported smoking habits in smoking pregnant women and estimate the prevalence of substantial exposure to passive smoking in non-smoking pregnant women. DESIGN: Retrospective, quantitative study, consecutively collected samples. SETTING: One antenatal clinic in Blekinge County, Sweden. SUBJECTS: 509 pregnant women. METHOD: Information about smoking habits were taken from the antenatal records of 496 women (97%). Serum samples from these women were tested for cotinine, a nicotine metabolite. MAIN OUTCOME MEASURES: Self-reported smoking habits and cotinine levels in ng/mL. RESULTS: Of 407 women, reporting to be non-smokers, 6% were most likely smokers, and 3% had cotinine levels suggesting exposure to substantial passive smoking. Of 60 women, reporting smoking 1-10 cigarettes per day, 32% were likely to smoke more. CONCLUSION: If the true facts about exposure to tobacco smoke are not revealed, a number of women who might benefit from information and support at the antenatal clinic will miss the opportunity of such assistance, resulting in increased risks for both the woman and her fetus.     

Smoking during pregnancy increases the risk of preterm births among parous women

BACKGROUND: We wanted to study a possible association between smoking during pregnancy and preterm birth. METHODS: A population based prospective study was performed among 7,236 consecutive pregnancies over seven years delivered at one birth clinic. Smoking habits were obtained at a routine ultrasound examination around 18 gestational weeks, and preterm birth was defined as delivery of a child between 24 and 37 gestational weeks. We estimated relative risk (odds ratio) between smoking, possible confounding variables and preterm birth using multiple logistic regression analysis. RESULTS: Overall, 1,769 (25%) women said that they smoked every day during their pregnancy. The smoking women had an increased risk of preterm delivery compared with non-smokers (odds ratio 1.53, 95% confidence interval 1.24, 1.89). However, this association was only demonstrated among the multiparous women (odds ratio 1.88, 95% confidence interval 1.39, 2.54). The association was statistically significant after adjusting for maternal age, diabetes, cervical conization, preeclampsia, placental abruption and placenta previa in a multivariate analysis, and we observed a dose-response effect of maternal smoking on preterm birth among multiparous women. CONCLUSION: For multiparous women smoking during pregnancy increases the risk of preterm delivery, and there seems to be a dose-response effect of smoking.