Consequences of smoking during pregnancy for mother and child

Objective: to evaluate the consequences of maternal smoking Methods: a prospective study of 1.103 pregnant women. A survey in the state Hospital San Martin, de La Plata, Buenos Aires determined general data. Newborn and placenta data were also reported. Mother and child cord samples were obtained to determine blood elements and flow cytometry analysis of lymphocyte subsets performed. Data from smoking (S) and non-smoking (NS) groups were evaluated through relative risk, chi square and Student's t test. Results: of all patients, 887 were NS and 226 said they smoked over five-cigarettes/day (S). The S group showed a higher probability of premature deliveries when compared to the NS group, with newborns weighing under 2,5kg, small in relation to gestational age, with Apgar scores at the 5th minute under six and hyaline membrane syndrome; intrauterine death risk was higher in this group who attended less medical appointments than scheduled. Umbilical cord blood analysis indicated lower reticulocyte index for S mothers, neutrophil count and CD4/CD8 ratio and increased erythroblast, eosinophil, basophil, total and CD8+T lymphocyte counts. Conclusions: data could explain the observations by other authors related to an increased incidence of allergy and infections in newborns caused by maternal smoking.

Objetivos: avaliar as conseqüências para a mãe e para o filho do hábito de fumar durante a gestação.

Introduction
There is strong evidence indicating the relationship between tobacco and: cancer, heart, vascular or lung diseases driving authorities of many countries to implement sanitary policies such as the prohibition of smoking in certain public spaces (inside airplanes, museums, etc) all over the world.
However, smoking remains an individual choice for it is not possible to restrict the habit in private environments as one's own home.Health campaigns against tobacco are overwhelmed by tobacco industries'investments.
Smoking is extremely costly for all governments that annually spend millions of dollars treating tobacco's related diseases.A clear example of this has been published by the National Hospital Discharge Survey (NHDS), reporting the expenses incurred by private health insurance companies in the United States of America at 167 million dollars annually to treat tobacco 1 related complications.
Smoking, notwithstanding being detrimental to health, it is, as previously mentioned, a personal choice.Nevertheless, there are two situations impacting the health of others: a) one is the case of passive smokers, for smokers contaminate the air surrounding them, forcing others to inhale it.This can be avoided by restricting smoking to specific areas or by prohibiting smoking in certain environments, etc; b) a more severe situation when compared to the previous one is when "passive" smokers have no way out and are forced to live and breathe in the same environment.That is the case of babies when their mothers continue smoking during pregnancy.
Smoking during pregnancy has being associated to complications such as previous placenta, 2 placenta's detachments, 3 and undersized newborns. 4,5A prospective study was carried out in pregnant smoking and non-smoking mothers and their children, with the purpose of determining the effects of smoking during pregnancy.

Methods
A survey was accomplished during the time of pregnancy diagnosis to determine what patients should be included in the study.
1.103 pregnant women attending to State Hospital San Martín of La Plata, Ministry of Health, Buenos Aires, Argentina were included in a prospective study between April and August of 1999.They were clinically followed up until January 2002.
The group was comprised of patients daily smoking five cigarettes or more during pregnancy.Exclusion criteria were known prior pathology (arterial hypertension, diabetes) and other conditions detected by the initial control such as severe anemia (<9gr/dl), and women in any kind of drugs other than nutrition supplements prescribed by the status' nutritional therapy.
The data requested was age, initial weight, whether the respondents were smokers or nonsmokers and amount of cigarettes consumed daily.At parturition's time, a new survey was accomplished to confirm whether or not the women had continued smoking during the course of pregnancy, as well as the daily quantity of cigarettes consumed.
Weight at delivery time, gestational age, Apgar score of the new born at the first and five minutes after birth, baby's weight, and placenta's weight were some of the analyzed data.Cord blood samples from smoking and non-smoking mothers were analyzed by a double blind laboratory method.From each sample, the following information was collected: hematocrite, hemoglobin, red cells, reticulocytes and leukocytes recounts, leukocyte subtypes formula, platelets recount, T and B lymphocytes subtype, natural killer (NK) absolute number of cells CD3, CD4, CD8, CD19, CD3-/CD56+ (NK) and CD4/CD8 ratios.Erythrocytes, leukocytes and platelets tests were performed through an automatic cellular counter (Microcell counter Sysmex F-803), hematocrites were confirmed by reticulocyte microcentrifuge, dyeing was performed by crescile blue brilliant and for the leukocitary formula smear analysis was performed by optic microscopy.The following panel was used to determine the sub-types of lymphocyte in the samples: g1/g1, CD3/CD4, CD3/CD8, CD3/CD56, CD19, all were conjugated with fluorescein or pico-erythryn (FITC or PE) and posterior flowcytometry reading (Coulter Epics XL).For the analysis of patient's and newborn's data, the perinatal computer system from the Pan-American Health Organization (PAHO) and World Health Organization (WHO) was used.Relative risk and chi square values were used to establish the different variable ratios of both groups (smoking and nonsmoking mothers), the confidence interval used was of (95%CI).For the assessment of numerical hematological and immunological variables the t Student test was used to compare the groups of smoking and non-smoking mothers and their babies.For variables' homogeneity testing the Barlett's chi square test was used.

Results
Of the 1.103 patients in the study, 877 were included in the non-smoking group (NS) and 226 in the smoking group (S).
Only 2,58% of the smoking patients at the time pregnancy was diagnosed, ceased smoking during the course of pregnancy.
The number of medical visits attended were less than the five visits scheduled in 64,06% in S group and 50,05% in non-smoking group (Table 1  Gestational age was younger in S than in NS (p <0,001) while the risk of intrauterine death was highly increased in the smoking mothers (p = 0,004).
Mothers exposed to tobacco had an increased risk of delivering babies under 2.500mg (p <0,001).
The ratio of new-born weight and gestational age was also smaller in the group of smokers when compared to the NS group (p = 0,003).
An Apgar score under six points at the first minute after birth was the same for both groups in the study, however, when the test was applied after five minutes, a higher risk of Apgar values under six in smoking mothers'babies was determined (p = 0,02).

Table 3
Haematological data (X ± SD) referring to leukocyte differential count in umbilical cord blood.

Table 4
Immunological data (X ± SD) referring to umbilical cord blood.

Discussion
Prior studies have shown that maternal smoking during pregnancy causes a higher incidence of previous placenta, 2 placental detachment, 3 and low weight newborns.
The association prenatal exposure to tobacco and newborns affected by allergies, 4 asthma, [5][6][7][8] abnormal lung development, 9 neonatal lung dysfunctions, 10,11 pulmonary infections, 12 decrease in the Apgar score at the first minute 13 and increase of sudden death 14 events has been determined.Posterior evaluation of these children has determined that they tend to have concentration impairments in school. 15][18] Other authors reported that fetal blood samples from smoking mothers had reduced numbers of neutrophiles, 19 as well as higher erythropoietin levels. 20ur study confirms some of these tendencies and adds new ones.Data obtained in this study show significant high risk for smoking mothers to deliver premature and underweight babies (<2.500mg), intrauterine death, small babies in relation to gestational age, Apgar score less than six after five minutes, and hyaline membrane syndromes.It has also been determined that the majority of mothers in the S group attended less than five medical visits during pregnancy as compared to the NS group.It is possible that these women did not attend medical visits because they were not willing to stop smoking during pregnancy.
Considering neutrophil decrease exists in babies with smoking mothers, it is clear that this will result in certain degree of immunodeficiency, predisposing them to several infections.CD4/CD8 ratio decrease, also observed in cord blood from the S group, is probably due not only to a decrease in the CD4 cells absolute number, but also to an increment in CD8 levels.The high eosinophils percentage determined in the S group as opposed to the NS group, ecould be correlated with allergic problems and the lung permeability increase described in these babies.
Considering pregnancy is a period of the life in which women become aware they are no longer by themselves and must look after their babies, it has been proven they are prone to abandon old addictions like tobacco. 21owever, according to our data, only few women from the study gave up smoking during pregnancy.Many times, pregnancy is a good excuse to stop the habit of smoking by the whole family. 21ontrolled studies performed to evaluate programs promoting tobacco abandonment during pregnancy have indicated these are successful. 22Randomized studies, confirm that simple medical advice has been enough to reduce the habit of smoking in over 50% of pregnant women. 23It would be desirable then to use this stage to promote programs encouraging women to quit smoking during pregnancy. 24

Conclusions
Smoking during pregnancy increases the probability of intrauterine deaths, premature and underweight babies, inadequate weight and gestational period ratio, an Apgar score <six at five minutes and hyaline membrane condition.Smoking mothers attended less medical visits than scheduled during pregnancy.Changes were also detected in: conformation of leucocytes, erithrocytes, and eosinophiles increase, basophiles, lymphocytes and eritroblasts.This could explain the predisposition these children have to infections or complications early in their lives.
Our study determined a very low tendency of pregnant women to quit smoking during pregnancy.A program implemented by health professionals explaining the consequences of smoking during pregnancy could be able to revert this tendency and improve the health of pregnant women and their babies.

161 Smoking during pregnancyTable 1
).Relative frequency and relative risk of variables.