***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: We report the results of a population -based r and omized clinical trial that tested the effectiveness of a prenatal self-help smoking  cessation program . The intervention consisted predominantly of printed material s received through the mail .  The population ( n = 242 ) consisted of a socioeconomically and ethnically diverse group of pregnant women enrolled in a large health maintenance organization ( HMO ) who reported they were smoking at the time of their first prenatal visit . Biochemical confirmation of continuous abstinence achieved prior to the 20th completed week of pregnancy and lasting through delivery revealed 22.2 per cent of the women in the eight-week serialized program quit versus 8.6 per cent of controls with usual care . The adjusted odds ratio was 2.80 ( 95 per cent CI = 1.17 , 6.69 ) . We conclude that a low-cost prenatal self-help intervention can significantly affect the public health problem of smoking during pregnancy and its associated risks for maternal and child health BACKGROUND Maternal smoking during pregnancy is recognized as an important and modifiable risk factor for low infant birthweight . The objective of this study was to compare the effects of maternal smoking status on prenatal weight gain and infant birthweight , and to determine if maternal weight gain mediates the effect of smoking cessation on infant birthweight . METHODS This prospect i ve study of 341 white , non-Hispanic pregnant smokers , never smokers , and women who stopped smoking during pregnancy used multivariate analysis of variance to evaluate prenatal weight gain patterns . Multiple regression was used to investigate the effects of smoking status and maternal weight gain on infant birthweight . RESULTS Women who stopped smoking gained on average 39.68 lb during pregnancy . Smokers gained 32.75 lb , and never smokers gained 34.16 lb . Women who stopped gained significantly more weight than both smokers and never smokers ( p = 0.01 ) . Rates of weight gain differed significantly beginning in the second trimester , when women who stopped smoking gained more weight than never smokers ( 2.57 lb , 99 % CI = 0.46 , 8.07 ) and continued during the third trimester , with those who stopped smoking gaining more weight than both smokers ( 4.31 lb , 99 % CI = 1.88 , 12.00 ) and never smokers ( 1.25 lb , 99 % CI = 0.56 , 10.49 ) . Infant birthweight differences were significant for women who stopped smoking versus continuing smokers ( 292 g , 99 % CI = 145 , 440 ) and for never smokers versus continuing smokers ( 253 g , 99 % CI = 104 , 401 ) . Controlling for baseline maternal body mass index and infant gender , smoking status and weight gain each contributed significantly to infant birthweight ( p < 0.001 ) . No evidence of interaction between smoking status and weight gain on infant birthweight was found . CONCLUSIONS Maternal smoking status significantly affects prenatal weight gain and infant birthweight , but smoking cessation protects against lower birthweight through mechanisms other than increased maternal weight gain or different weight gain patterns BACKGROUND Physicians ' advice to help pregnant women quit smoking during prenatal care has had mixed results . Training and prompting physicians to provide consistent advice and referral to on-site support might improve cessation rates . METHODS Pregnant women who smoked were r and omly assigned to receive structured advice from their physician and referral to individual behavior change counseling during prenatal care or to receive brief advice to stop smoking and a quit smoking booklet at their first visit .  Smoking status was measured by self-report , exhaled carbon monoxide , and urinary cotinine . RESULTS Compared with usual care , greater proportions of intervention group women reported not smoking at the 36th-week visit ( 14 % vs 10 % ) and at 1 year postpartum ( 18 % vs 11 % ) , but these differences were not significant . However , significantly greater proportions of intervention group women reported either not smoking or reducing their cigarette consumption by 50 % or more at their second visit ( 43 % vs 29 % , P = 0.02 ) , at their 36th-week visit ( 40 % vs 25 % , P < 0.01 ) , and at 1 year postpartum ( 26 % vs 14 % , P = 0.02 ) . CONCLUSIONS Physician training on how to gain a pregnant smoker 's commitment to change her smoking behavior , an office prompt system , and individualized smoking behavior change counseling show promise in reducing smoking during pregnancy and postpartum , but practical methods to assist pregnant smokers between regular prenatal visits , as they attempt to quit , need to be developed This article evaluates the evidence to support the use of biochemical measurement of significant reduction ( SR ) rates among pregnant smokers as a new behavioral indicator of “ harm reduction ” ( HR ) . The results of four studies —three r and omized patient education clinical trials of pregnant smokers ( Trials I , II , and III ) and an epidemiological study ( Study IV)—are presented . Among Trial I , II , and III cohorts of pregnant smokers , control group SR rates of 7 % ( I ) , 9 % ( II ) , and 20 % ( III ) were increased among experimental groups to 17 % ( I ) , 18 % ( II ) , and 32 % ( III ) by the same patient education methods . Analyses of infant birthweight data in Study IV found that a patient SR rate representing a 50 % or more decrease between a baseline and follow-up test was associated with an increase in adjusted birthweight of 92 grams OBJECTIVE Our objective was to determine the effectiveness of training obstetric and family practice residents to provide smoking cessation advice . STUDY DESIGN The effectiveness of the trained residents '  advice was assessed from exit interviews of pregnant smokers taking part in a r and omized , controlled trial of smoking cessation advice .  Exit interview responses were compared by chi 2 analysis . RESULTS Training result ed in significant changes in the advice provided by the residents , with greater emphasis on gaining a commitment to smoking behavior change , but not in the average time providing the advice , approximately 3 minutes . Adherence to the protocol was maintained at 80 % . Significantly more women who received the brief structured advice agreed to stop smoking ( 54 % ) or cut down their cigarette consumption ( 28 % ) compared with women in the control group ( 14 % and 6 % , respectively ) , p = 0.0001 . CONCLUSION The structured advice consistently provided by the trained residents was effective in gaining commitments from pregnant smokers to change their smoking behavior Purpose . Despite high rates of spontaneous and assisted smoking cessation during pregnancy , postpartum maintenance is disappointingly low . Predictors of return to smoking remain unclear , thus limiting the development of interventions that could protect the health of women and their children . This study followed women who had participated in a prenatal smoking cessation intervention trial and successfully stopped smoking to address two aims : ( 1 ) describe the probability of relapse in confirmed quitters during the first 6 months after the birth , and ( 2 ) identify factors that increase relapse . Design . Prospect i ve design during pregnancy and retrospective report at 6 months postpartum used survival analysis with return to smoking as the dependent variable and the Cox proportional hazards regression technique . Measures . Question naires were used at the first prenatal visit and telephone interviews at the 26th week of pregnancy and 6 months postpartum . Nonsmoking after the 20th week was measured by urine cotinine tests ( m = 3 ) ; nonsmoking postpartum was measured by retrospective self-report . Setting . The setting was an HMO-based group practice in Los Angeles . Subjects . Subjects were white , black , and Hispanic women ( n = 127 ) available for follow-up . Results . The proportion of the sample classified as relapsers at 6 months postpartum was 62.9 % . The final model identified the following risk factors for smoking : taking puffs in late pregnancy and having friends who smoke at the first prenatal visit , less confidence in mid-pregnancy that they could maintain nonsmoking postpartum , and a partner who smokes postpartum . Conclusions . Intervention should begin in late pregnancy , and smoking networks , including partner smoking , should be addressed This article presents the methodology and baseline findings of a large multicenter trial involving four countries from Latin America ( Argentina , Brazil , Cuba , and Mexico ) . The study was a r and omized , controlled , single-masked trial to investigate the impact of social support during pregnancy on perinatal outcomes . Pregnant women with gestational ages between 15 and 22 weeks were screened in health facilities in the four countries . Those presenting with one or more risk factors for having a low-birthweight baby were invited to join the trial . A total of 2235 women -- between 500 and 600 in each country -- were r and omized into an intervention ( n = 1110 ) or a control ( n = 1125 ) group . Both groups were comparable in terms of nearly all baseline variables . The intervention group received a minimum of four visits at home by a trained health worker who provided direct emotional support , health education , and an attempt to enhance the woman 's social support network . Over 90 % of all women were evaluated at 36 weeks of pregnancy and soon after delivery , and 85 % at the 40th day postpartum . The outcomes under study included intrauterine growth retardation , gestational age , perinatal and maternal morbidity and mortality , labor interventions , psychological distress and characteristics of the social support network , among others . This trial showed that it was possible to select , screen , r and omize , visit , and evaluate a large number of women in four Latin American countries using a st and ardized methodology This study was undertaken to determine 1 ) whether reducing tobacco exposure during pregnancy increases the birth weight of term infants and 2 ) the relative effects of early- and late-pregnancy exposure to tobacco on infant birth weight . Data were obtained from the Smoking Cessation in Pregnancy project , conducted in public clinics in three states ( Colorado , Maryl and , and Missouri ) between 1987 and 1991 .  Self-reported cigarette use and urine cotinine concentration were collected from 1,583 pregnant smokers at study enrollment and in the third trimester . General linear models were used to generate mean adjusted birth weights for women who reduced their tobacco exposure by 50 percent or more and for those who did not change their exposure . Regression smoothing techniques were used to characterize the relation between birth weight and early exposure and birth weight and third-trimester exposure . Reducing cigarette use was associated with an increase in mean adjusted birth weight of only 32 g , which was not significant ( p = 0.33 ) . As third-trimester cigarette use increased , birth weight declined sharply but leveled off at more than eight cigarettes per day . Findings were similar when urine cotinine concentration was used . Women who smoke during pregnancy may need to reduce to low levels of exposure ( less than eight cigarettes per day ) to improve infant birth weight The purpose of this prospect i ve , r and omized controlled study was to determine the efficacy of an intensified , late pregnancy , smoking cessation intervention for resistant pregnant smokers ( n = 269 ) . Participants received 3 - 5 min of counseling plus a self-help booklet at their first prenatal visit and seven booklets mailed weekly thereafter ; at 28 weeks , all had been smoking in the past 28 days . The experimental group received a stage of change-based , personalized feedback letter and two telephone counseling calls using Motivational Interviewing ( MI ) strategies . The control group received care as usual . The 34th week cotinine data demonstrated no overall difference between groups . However , an implementation analysis suggested that 43 % of women who received the full intervention ( E2 ) were classified as not smoking compared to 34 % of the control group . At 6 weeks postpartum , 27.1 % of the E2 group reported being abstinent or light smokers vs. 14.6 % of the controls . No differences were detected at 3 and 6 months postpartum . Results lend preliminary but very modest support for this intervention with resistant pregnant smokers . Improvements in the intervention and implementation issues are discussed Smoking is a major modifiable risk factor in pregnancy , and low-cost interventions have been developed and tested in diverse population s of pregnant smokers . Successful intervention depends on identification , however , and nondisclosure can be a problem . This r and omized study compared rates of disclosure with two response formats -- multiple choice , in which the patient is able to describe herself as having " cut down , " and the usual history question , " Do you smoke ? , " in which she is forced to answer simply " yes " or " no " . Each format was tested in both oral and written channels with a multiethnic adult prenatal population ( n = 1078 ) entering care in a multispecialty group . Study results indicate that the multiple choice question  improved disclosure , regardless of channel ( oral versus written ) , by 40 % . This effect was observed across racial and ethnic groups . Biochemical tests of urine sample s from reported nonsmokers indicated smoking in only 3 % . Eleven percent of the " nonsmokers " in the experimental groups refused consent for the urine test , however , and many of these were probably smokers AIMS Two methods of dissemination ( simple and intensive ) were used to disseminate a smoking cessation programme to doctors and midwives working in antenatal clinics . This paper describes the differential uptake of the smoking cessation programme by doctors and midwives . It investigates whether the number of smoking cessation interventions used differ due to the type of dissemination . It also examines the frequency 
    Output:
    
The single large cluster-r and omised trial showed no evidence of a decrease in continued smoking or adjusted mean birthweight .
REVIEW ER 'S CONCLUSIONS Smoking cessation programs in pregnancy appear to reduce smoking , low birthweight and preterm birth , but no effect was detected for very low birthweight or perinatal mortality