早期妊娠妇女人工流产的因素调查

目的：了解早期妊娠行人工流产妇女的人群特征,探讨导致妇女人工流产的相关因素,为减少非意愿妊娠提供干预依据。方法：采用整群抽样方法,对丰台区四家二级医院计划生育门诊同期行人工流产的妇女进行问卷调查。结果：共回收调查问卷4381份。调查对象中,平均年龄26岁（16．54岁）,本市户籍占26．8％,外地户籍73．2％;已婚65．33％,未婚34．67％;文化程度初、高中占62．5％;职业列前三位的分别是服务员23．5％、公司职员18．2％、个体工商户10．5％;重复流产为37-3％。非意愿妊娠占83．24％,,非意愿妊娠的原因,39．53％是未避孕,43．71％为避孕失败,而避孕失败的原因中又以避孕套避孕失败居首;意愿妊娠占Ⅲ6．7鹞％,最终选择终止妊娠的原因分别为个人工作因素、情感因素及优生考虑。结论i为降低l妇女非意愿妊娠及重复流产率,对育龄妇女,尤其是流动、未婚人群,需广泛开展性健康教育及避孕方式知情选择,加强避孕知识以及人工流产危害的宣教,指导避孕方法的正确使用,同时,各级医院亟待开展流产后服务。     

A study of contraception as related to unwanted pregnancy

A study was made of 150 women requesting therapeutic abortion. Mechanical failure of the contraceptive method used accounted for unwanted pregnancy in 89 (59%) women. In the remainder no method of contraception was used by either partner. Among women requesting abortion, failure to use contraceptives was commoner in the younger and unmarried than in older and married women.The data obtained were analyzed in an attempt to explain the failure and avoidance of contraception. Suggestions are made as to how to discourage the use of abortion as a method of contraception.     

Legal abortions among teenagers in Canada, 1974 through 1978.

Between August 1969, when the amendment to the Criminal Code went into effect, and December 1978 about 397 000 legal abortions were performed in hospitals with therapeutic abortion committees in Canada. During the 5-year period 1974-78 abortions in females under 20 years of age accounted for 30.9% of all the legal abortions performed in Canada on Canadian residents, and the abortion rate per 1000 women aged 15 to 19 years increased from 13.6 to 16.3. During 1974-77 the proportion of women in whom the gestation period was more than 12 weeks at the time of abortion was 25.3% for teenagers (females under 20 years of age) but only 14.6% for women aged 20 years or over. In 1976 the teenage abortion rate was lower in Canada (14.5) than in the United States (36.2%), Sweden (28.5), Hungary (26.4), Denmark (26.0), Norway (22.7), Finland (20.3), and England and Wales (15.4).     

Induced abortion in Sri Lanka: who goes to providers for pregnancy termination?

The sociodemographic characteristics of abortion seekers and the reasons they give for procuring termination were studied in 356 clients selected from two abortion clinics in the city of Colombo. Nearly 80% were Buddhists and about 10% were Christians. Almost all had some formal education but only 20% were employed outside the home. Over 95% were currently married and at the peak of their childbearing age. More than one-half were aged 30 years or over, while adolescents only constituted about 3%. Fourteen per cent were nulliparous and about two-thirds had one or two living children at the time of obtaining the abortion. A significantly high proportion also had a very young child. In total, the 356 women had had 1130 pregnancies, and the mean rate of abortion was 42 per 100 pregnancies. Over one-quarter had had more than one abortion and about 10% had had three or more. Almost all abortions were performed within the first trimester with a mean gestation period of 6 weeks. About one-third of the clients were using some method of contraception at the time they became pregnant. The most common reasons cited for the present abortion were 'pregnancy too soon after previous delivery', 'no more children desired' or 'curtailment of opportunity for foreign employment'. Unmarried women constitute a special group of abortion seekers who have different needs and behave differently from married women. Their needs are not currently being met by reproductive health programmes in Sri Lanka, and it is important that they should be given special attention in the future. An interesting finding is that a significant minority of the abortion seekers answered negatively to the question regarding providing medical facilities for abortions without difficulty. This underscores the ambivalence many people have to abortion.     

Factors associated with immediate abortion complications.

OBJECTIVE: To identify factors associated with increased risk of immediate complications from induced abortion. DESIGN: Retrospective analysis of a provincial database. SETTING: All Ontario general hospitals in which abortions are performed and all free-standing abortion clinics in Ontario. POPULATION: Women in Ontario aged 15 to 44 years who underwent an induced abortion in the province (without concurrent sterilization) between Jan. 1, 1992, and Dec. 31, 1993. OUTCOME MEASURES: Recording of complications at the time of the procedure, gestational age, type of procedure, place of abortion (hospital or clinic), and patient''s age, parity and history of previous abortion (spontaneous or induced). RESULTS: During the study period 83 469 abortions were performed that met our inclusion criteria. Immediate complications were reported in 571 cases (0.7%). Multivariate logistic regression analysis revealed that, after other variables were controlled for, the patient''s age, parity and history of previous abortions (spontaneous or induced) were not significant risk factors for immediate complications; however, gestational age, method of abortion and place of abortion were significant risk factors (p < 0.001). The odds ratio (OR) for having a complication from abortion was 1.3 (95% confidence interval [CI] 1.02 to 1.63) between 9 and 12 weeks, compared with having one after abortion at 9 weeks or earlier, and increased to 3.3 (95% CI 2.23 to 5.00) after abortion between 17 and 20 weeks. Compared with surgical dilatation and curettage (D&C), instillation of saline and instillation of prostaglandins were more likely to be associated with immediate complications (OR 24.0, 95% CI 13.22 to 43.70, and OR 11.7, 95% CI 6.43 to 21.18, respectively), whereas both suction D&C and insertion of a laminaria tent were less likely to be associated with immediate complications (OR 0.4, 95% CI 0.26 to 0.67, and OR 0.3, 95% CI 0.19 to 0.52, respectively). Compared with women who had an abortion in a free-standing clinic, the risk for immediate complications was greater among those who had an abortion in a hospital, especially a teaching hospital (OR 1.9, 95% CI 1.38 to 2.58), a nonteaching hospital with 200 to 399 acute care beds (OR 3.1, 95% CI 2.27 to 4.21) and a nonteaching hospital with fewer than 200 acute care beds (OR 5.9, 95% CI 4.04 to 8.64). CONCLUSION: The risk of immediate complications from induced abortion is very low. Unlike in previous studies, the woman''s age, parity and history of previous spontaneous or induced abortions were not found to be risk factors. However, advancing gestational age and procedures involving instillation of saline or prostaglandins were predictive factors of immediate complications.     

Contraception and Unintended Pregnancy among Unmarried Female University Students: A Cross-sectional Study from China

This study aims to understand the level of contraceptive knowledge and attitudes towards contraception, and then to explore the association between the contraceptive behavior and unintended pregnancy in unmarried female university students in China. A cross-sectional study was conducted of university students in 49 universities across 7 cities in China from September 2007 to January 2008. We distributed 74,800 questionnaires, of which 69,842 were returned. In this paper, the data from 35,383 unmarried female university students were analyzed. The prevalence of sexual intercourse in unmarried female university students was 10.2%. The prevalence of unintended pregnancy in those sexually active female university students, was 31.8%. Among students with pregnancy, 53.5% experienced two or more pregnancies. 28.3% of the students with sexual intercourse reported that they always adopted contraceptive methods, and of those 82.9% chose to use male condoms. The majority (83.9%) of students with unintended pregnancy chose to terminate the latest pregnancy by surgical abortion or medical abortion. The contraceptive knowledge level of students who experienced unintended pregnancy was lower than those who did not. In China, about one third of unmarried female students with sexual intercourse experience unintended pregnancy. A variety of contraceptive methods are adopted, but the frequency of contraceptive use is low. Most of unmarried female students who experienced unintended pregnancy would choose to terminate the pregnancy with surgical or medical abortion. University students, especially the ones who have experienced unintended pregnancy, lack contraceptive and reproductive health knowledge.     

Reproductive mortality.

The transfer from traditional to modern methods of contraception in recent decades has been accompanied by a transfer of deaths from complications of pregnancy to deaths from complications of the modern contraceptive methods. In 1975, for example, it is estimated that there were more deaths at ages 25-44 years in England and Wales from adverse effects of oral contraceptive use than from all complications of pregnancy, delivery, and the puerperium combined. Thus maternal mortality is no longer an adequate indicator of the deaths associated with reproduction in the community. An alternative measure, the reproductive mortality rate should be used, which includes deaths from complications of contraceptive use as well as those from complications of pregnancy or abortion. The reproductive mortality rate in England and Wales seems to have declined continuously since 1950 for women aged 25-34. But after 1960 it increased for women aged 35-44, because of the higher mortality associated with oral contraceptive use in this age group.     

Hospital Admission following Induced Abortion in Eastern Highlands Province,Papua New Guinea – A Descriptive Study

Background

In Papua New Guinea abortion is restricted under the Criminal Code Act. While safe abortions should available in certain situations, frequently they are not available to the majority of women. Sepsis from unsafe abortion is a leading cause of maternal mortality. Our findings form part of a wider, mixed methods study designed to identify complications requiring hospital treatment for post abortion care and to explore the circumstances surrounding unsafe abortion.

Methods

Through a six month prospective study we identified all women presenting to the Eastern Highlands Provincial Hospital following spontaneous and induced abortions. We undertook semi-structured interviews with women and reviewed individual case notes, extracting demographic and clinical information.

Findings

Case notes were reviewed for 56% (67/119) of women presenting for post abortion care. At least 24% (28/119) of these admissions were due to induced abortion. Women presenting following induced abortions were significantly more likely to be younger, single, in education at the time of the abortion and report that the baby was unplanned and unwanted, compared to those reporting spontaneous abortion. Obtained illegally, misoprostol was the method most frequently used to end the pregnancy. Physical and mechanical means and traditional herbs were also widely reported.

Conclusion

In a country with a low contraceptive prevalence rate and high unmet need for family planning, all reproductive age women need access to contraceptive information and services to avoid, postpone or space pregnancies. In the absence of this, women are resorting to unsafe means to end an unwanted pregnancy, putting their lives at risk and putting an increased strain on an already struggling health system. Women in this setting need access to safe, effective means of abortion.     

Before and after therapeutic abortion

Surveys conducted after therapeutic abortion were used to evaluate contraceptive use, to assess early physical and emotional effects and to provide feedback to the hospital nurses on their counselling role. The follow-up rate was only 53%. Of those who cooperated 82.9% were using effective contraception three months after abortion. Subjective morbidity was greater than anticipated. The main emotional response was relief coupled with some guilt and depression in a significant minority. The occurrence and significance of the after effects of abortion should be explained in advance. Training workshops for abortion counsellors would be useful. The surgical termination of pregnancy is only a small part of a comprehensive abortion service.     

Abortion as a backup method for contraceptive failure in China

Contraceptive failure rates for modern methods including sterilization are reported to be high in China, but little is known about the consequence of contraceptive failure and characteristics of women who decide to have an abortion if a contraceptive failure occurs. Using 6225 contraceptive failures from the 1988 Chinese Two-per-Thousand Fertility Survey, this study examines the resolution of contraceptive failure and assesses the impact of some women's sociodemographic characteristics on the decision to terminate contraceptive failure in abortion. This study has three important findings: (1) The abortion rate was 50.1%, 75.3% and 80.2% for IUD, condom and pill failures, respectively; (2) The abortion rates differed by contraceptive method and women's social and demographic characteristics. In particular, a woman with just one child was most likely to have the contraceptive failure aborted; (3) Some women experienced repeated abortions because of contraceptive failure. The results suggest that abortion was a backup method if contraception failed in China and the correlates of aborting an unwanted pregnancy reflect the strong impact of the Chinese family planning programme.     

Factors associated with uptake of post-abortion family planning in Shire town,Tigray, Ethiopia

Objectives

Post-abortion contraceptive service is pivotal for the prevention of unwanted pregnancy and alleviation of its complication. Worldwide half of the pregnancy is unplanned, whereas unwanted pregnancy ends up with abortion. This study assessed post-abortion contraceptive uptake and associated factors among abortion service users at health institution in Shire town, North Ethiopia. Institutional based cross-sectional study was conducted from December 15/2016 to March 15, 2017, in Shire town. Data were collected using systematic random sampling technique. Bivariate and multivariable analyses were done to determine the association of each independent variable with the dependent variable.

Results

Overall post-abortion contraceptive utilization in this study was 61.5%. Married [AOR 2.59, 95% CI (1.16, 5.65)], completed College education [AOR 5.69, 95% CI (1.61, 20.11)], previous contraceptive used [AOR 3.62, 95% CI (1.77, 7.40)], counseling of family planning [AOR 3.53 95% CI (1.69, 7.37)], grand multipara [AOR 7.91, 95% CI (1.66, 37.74)] and public health institution [AOR 5.95, 95% CI (3.03, 11.72)] were significantly associated with the post-abortion contraceptive utilization. In this study, post-abortion contraceptive utilization was about two-third. Being married, had been completing a college education, had been receiving family planning counseling, previous contraceptive usage, abortion care service at public health institution, and being grand multiparty were determinants of post-abortion contraceptive utilization.

     

Effects of oral contraceptive use on body mass index and blood pressure among female villagers in north-east Thailand

The use of contraceptives has become prevalent among females in Thailand in the past 20 years, and oral contraceptive use has been suggested to trigger changes in fat intake, energy expenditure, fat metabolism and blood pressure. Based on field investigations of 391 married women aged 20 years or over in Yasothon Province, North-east Thailand, this study aims to elucidate the effects of oral contraceptive use on body mass index (BMI: kg/m2) and blood pressure, taking into account reproductive histories and socioeconomic conditions. The proportion of obese (BMI > or = 25) subjects was high in the age groups 30-39, 40-49 and 50-59, accounting for, respectively, 39.4%, 51.1% and 48.5% of these populations. The proportion of women with hypertension (90/140 mmHg) was 23.7%, 18.5% and 26.2% in the 40-49, 50-59 and 60-69 age groups. Current contraceptive practices in the studied population included sterilization by operation, oral contraception and injection. These methods accounted for 43.0%, 12.8% and 8.2% of the population, respectively. Sociodemographic factors such as reproductive history, years of education and household income were not significantly related to BMI or to blood pressure (ANOVA with age adjustment). In contrast, oral contraceptive users had significantly higher BMIs and diastolic blood pressures (p<0.01, ANOVA with age adjustment). Multiple regression analysis also revealed that oral contraceptive use was a weak but significant contributing factor to both high BMI and blood pressure when sociodemographic factors were taken into account and controlled for statistically. It can thus be concluded that the use of contraceptive pills, which contain oestrogen and progestin and are provided free of charge to Thai women, tend to increase BMI and to elevate blood pressure.     

‘This Is Real Misery’: Experiences of Women Denied Legal Abortion in Tunisia

Barriers to accessing legal abortion services in Tunisia are increasing, despite a liberal abortion law, and women are often denied wanted legal abortion services. In this paper, we seek to explore the reasons for abortion denial and whether these reasons had a legal or medical basis. We also identify barriers women faced in accessing abortion and make recommendations for improved access to quality abortion care. We recruited women immediately after they had been turned away from legal abortion services at two facilities in Tunis, Tunisia. Thirteen women consented to participate in qualitative interviews two months after they were turned away from the facility. Women were denied abortion care on the day they were recruited due to three main reasons: gestational age, health conditions, and logistical barriers. Nine women ultimately terminated their pregnancies at another facility, and four women carried to term. None of the women attempted illegal abortion services or self-induction. Further research is needed in order to assess abortion denial from the perspective of providers and medical staff.     

血清妊娠相关血浆蛋白A在诊断异常妊娠中的临床意义

目的:探讨血清妊娠相关血浆蛋白A(PAPP-A)在诊断异常妊娠中的临床意义,分析其与异常妊振的关系。方法:选取299例5~13周的正常早孕妇为正常早孕组,同期选取稽留流产86例,先兆流产54例,异位妊娠76例为异常妊娠组,用酶联免疫吸附试验(ELASA)测定两组受试者的血清PAPP-A水平,分析两组受试者各个孕周内的血清PAPP-A水平的差异。结果:稽留流产孕妇在各个孕周内(9~13周)的血清PAPP-A水平显著低于同孕周内正常早孕孕妇(t值分别为9.500,8.113,3.511,9.538,8.504,P值均0.05);稽留流产孕妇总的平均血清PAPP-A水平亦低于常早孕孕妇(t=3.651,P值均0.05);异位妊娠孕妇在各个孕周内(9~13周)的血清PAPP-A水平显著低于同孕周内正常早孕孕妇(t值分别为7.976,9.030,9.941,11.625,14.079,12.569,P值均0.05),异位妊娠孕妇总的平均血清PAPP-A水平亦低于常早孕孕妇(t=28.168,P值均0.05);先兆流产孕妇(除孕8周)与正常早孕妊娠血清PAPP-A水平比较无显著统计学意义。结论:血清PAPP-A水平在异常妊娠如异位妊娠、稽留流产中显著降低,可作为诊断异位妊娠、稽留流产及先兆流产辅助诊断的生物学指标。     

Effectiveness of abortion as birth control.

Several models used to study the effectiveness of abortion in population limitation are examined. The Keyfitz model, based on the probability that an individual woman will conceive in a given month, is extended and public implications of legal abortions are discussed. A model more appropriate for a population of women rather than a single woman can be developed by relating the probability of conception and the sterile intervals to the number of birth and the number of women in the population. The effectiveness of abortion as a birth control method is studied using this model and includes: 1) abortion effectiveness combined with efficient contraception (95% effective); 2) the sensitivity of abortion to gestation when a contraceptive of lower efficiency is used; 3) these effects modified for prolonged lactation; 4) the effect of changing the monthly probability of conception and the monthly efficiency of contraception. Abortion later in pregnancy is advantageous when efficient contraception is absent. The effectiveness of abortion to gestation is approximately the same whether lactation is included or absent, although abortion is more effective at all gestations and for all contraceptives efficiencies in the absence of lactation. The sensitivity of the effectiveness of abortion to the probability of conception decreases as monthly effectiveness of contraception increases. The probability of conception and the monthly effectiveness of contraception are difficult parameters to measure in the population. The effect of abortion averaged over the entire population at risk of pregnancy is different from its effect on certain subgroups. For U.S. females the probability of conception may be between .06 and .16, and from the model it is indicated that the effectiveness of abortion would be from 1 to 1.13 abortions per live birth. The application of the model suggests that the expenditures for abortion services in this population are a reasonable investment, although investment for efficient contraception is also suggested.     

Factors affecting acceptability of long-acting contraceptive injections in a rural Egyptian community

This study was carried out in 4 adjacent villages in Lower Eghypt with a combined population of 24,000. A team of social workers and physicians worked together to introduce the injectable contraceptive depomedroxyprogesterone acetate as a post-partum long-acting contraceptive to the community leaders and the villagers at several meetings and individual home visits. Post-partum women who agreed to use the drug were defined as acceptors (591) and those who did not were defined as rejectors (715). The incidence of polygamy was higher among the rejectors, and rejectors' husbands had more children from their other wives. Acceptors had more previous pregnancies and children of both sexes than rejectors. The interval between the last 2 pregnancies was shorter among the rejectors. A greater % of acceptors had previously used another contraceptive. The commonest reasons for rejection were desire for further pregnancy (69%), health problems (11%), and desire for another method of contraception (8%). Religious factors figured in only 3% of cases.     

Postnatal development of peroxisomal and mitochondrial enzymes in rat liver.

Subcellular organellles from livers of rats three days prenatal to 50 weeks postnatal were separated on sucrose gradients. The peroxisomes had a constant density of 1.243 g/ml throughout the life of the animal. The density of the mitochondria changed from about 1.236 g/ml at birth to a constant value of 1.200 g/ml after two weeks. The peroxisomal and mitochondrial fatty acid beta-oxidation and the peroxisomal and supernatant activities of catalase and glycerol-3-phosphate dehydrogenase were measured at each age, as well as the peroxisomal core enzyme, urate oxidase, and the mitochondrial matrix enzyme, glutamate dehydrogenase. All of these activities were very low or undetectable before birth. Mitochondrial glutamate dehydrogenase and peroxisomal urate oxidase reached maximal activities per g of liver at two and five weeks of age, respectively. Fatty acid beta-oxidation in both peroxisomes and mitochondria and peroxisomal glycerol-3-phosphate dehydrogenase exhibited maximum activities per g of liver between one and two weeks of age before weaning and then decreased to steady state levels in the adult. Peroxisomal beta-oxidation accounted for at least 10% of the total beta-oxidation activity in the young rat liver, but became 30% of the total in the liver of the adult female and 20% in the adult male due to a decrease in mitochondrial beta-oxidation after two weeks of age. The greatest change in beta-oxidation was in the mitochondrial fraction rather than in the peroxisomes. At two weeks of age, four times as much beta-oxidation activity was in the mitochondria as in the peroxisomal fraction. Peroxisomal glycerol-3-phosphate dehydrogenase activity accounted for 5% to 7% of the total activity in animals younger than one week, but only 1% to 2% in animals older than one week. Up to three weeks of age, 85% to 90% of the liver catalase was recovered in the peroxisomes. The activity of peroxisomal catalase per g of rat liver remained constant after three weeks of age, but the total activity of catalase further increased 2.5- to 3-fold, and all of the increased activity was in the supernatant fraction.     

Comparing the effectiveness of copper intrauterine devices available in Canada. Is FlexiT non-inferior to NovaT when inserted immediately after first-trimester abortion? Study protocol for a randomized controlled trial

ABSTRACT: BACKGROUND: We describe the rationale and protocol for a randomized noninferiority controlled trial (RCT) to determine if the Flexi-T380(+) copper intrauterine contraceptive device (IUD) is comparable in terms of effectiveness and expulsion rates to the most common Canadian IUD currently in use, NovaT-200, when placed immediately after a first-trimester abortion. METHODS: Consenting women choosing to use an IUD after an abortion for a pregnancy of less than 12 weeks of gestation will be randomized to device-type groups to receive immediate post-abortion placement of either a Flexi-T380(+) IUD, a device for which no current evidence on expulsion or effectiveness rates is available, or the Nova-T200 IUD, the only other brand of copper IUD available in Canada at the time of study initiation. The primary outcome measure is IUD expulsion rate at 1 year. Secondary outcomes include: pregnancy rate, method continuation rate, complication rates (infection, perforation), and satisfaction with contraceptive method. A non-intervention group of consenting women choosing a range of other post-abortion contraception methods, including no contraception, will be included for comparison of secondary outcomes. Web-based contraception satisfaction questionnaires, clinical records, and government-linked health administrative databases will be used to assess primary and secondary outcomes. DISCUSSION: The RCT design, combined with access to clinical records at all provincial abortion clinics, and to information in provincial single-payer linked administrative health databases, birth registry, and hospital records, offers a unique opportunity to determine if a novel IUD has a comparable expulsion rate to that of the current standard IUD in Canada, in addition to the first opportunity to determine pregnancy rate and method satisfaction at 1 year post-abortion for women choosing a range of post-abortion contraceptive options. We highlight considerations of design, implementation, and evaluation of the first trial to provide rigorous evidence for the effectiveness of current Canadian IUDs when inserted after first-trimester abortion.Trial registrationClinicalTrials.gov Identifier NCT01174225.     

Adolescents' decision-making and attitudes towards abortion in north-east Brazil

Three groups of adolescents are compared with regard to their own considerations of abortion and when they believe abortion is justified. One group of adolescents terminated their pregnancies (n=95), a second became pregnant and carried their pregnancies to term but considered abortion (n=68), and the third also carried their pregnancies to term but did not consider abortion (n=204). The study was carried out between 1995 and 1998 in Fortaleza, Brazil. Adolescents were interviewed at the time of their hospitalization or their first prenatal visit and again at 6 weeks and 1 year post-abortion or postpartum. Friends and family recommended abortion to at least half of the teenagers in each group. Teenagers who aborted were more accepting of abortion than those who did not abort, while those who considered abortion found the practice more justified than those who did not consider abortion. Teenagers who aborted became less accepting a year later, while those who did not consider abortion became more accepting. A better understanding of adolescent attitudes towards abortion and their decision-making process should help adults and professionals meet the needs of adolescents for support in the process and in the reduction of the number of unintended pregnancies in the future.     

Genital Yeast Infections

Genital yeast infection was studied in 533 women seen in a department of venereology. Yeasts were recovered in culture from 138 patients (26% of the total). Candida albicans accounted for 112 (81%) of the isolates and Torulopsis glabrata for 22 (16%); other yeasts were uncommon. There was no evidence that the presence of yeasts was related to age. 32% of the women who were taking an oral contraceptive harboured yeasts, compared with 18% of those who were not.The symptoms and signs of the women with yeast infections were compared with those with vaginal trichomoniasis and those with no evidence of genital infection. It seems that a clinical diagnosis of vaginal mycosis cannot be made with accuracy and that positive identification of yeasts is necessary; for this, cultural methods are the most satisfactory.