Extending lactational amenorrhoea in Manila: a successful breast-feeding education programme.

An experimental breast-feeding education programme conducted at the Philippine General Hospital in Manila demonstrated that women could be motivated to improve their breast-feeding practices and lengthen their period of lactational amenorrhoea in comparison to a control group. Mothers who participated in the programme breast-fed their babies more frequently, delayed the introduction of regular supplements, used fewer bottles and pacifiers and maintained night feeding longer than mothers who were not exposed to the positive breast-feeding messages. The programme was successful in lengthening the period of amenorrhoea among women with elementary, high school, or technical school education, but not among college-educated women. Different educational approaches may be necessary for women of different education levels.     

Correlation between subsequent lengths of postpartum amenorrhoea in a prospective study of breast-feeding women in rural Bangladesh.

The relationship between subsequent lengths of lactational amenorrhoea for individual women in a prospective study of breast-feeding women in Bangladesh was studied. The data indicate that previous length of amenorrhoea has significant predictive value for the subsequent length of amenorrhoea. Information on previous experience with lactational amenorrhoea should be therefore incorporated into guidelines for the introduction of family planning during lactation.     

Variability of breast sucking, associated milk transfer and the duration of lactational amenorrhoea.

Quantitative relationships between physical parameters of sucking, milk transfer and the duration of amenorrhoea were examined in normal mother-baby pairs under exclusive breastfeeding. Sucking pressures were recorded twice on the second and once on the fifth month after birth, during complete breastfeeding episodes, by means of a catheter attached to the nipple and connected to a pressure transducer, the signals of which were analysed by computer. Babies were weighed before and after each sucking episode to estimate milk transfer. In the first nursing episode after noon, 2-month-old babies sucked from 140 to > 800 times during 4-15 min from the first breast, obtaining from 20 to > 100 g milk. The physical parameters of sucking and milk transfer exhibited high inter-individual but low intra-individual variabilities. There were significant differences in the physical parameters of sucking and milk transfer efficiency between first and second breast and between the second and fifth months after birth. Milk transfer efficiency was inversely correlated with time occupied by non-sucking pauses > or = 1.5 s, and was directly correlated with mean intersuck intervals in the first breast and with duration of the sucking episode, number of sucks, mean pressure and area under the pressure curve in the second breast. There was no correlation between the physical parameters of sucking and duration of lactational amenorrhoea (n = 62). However, significantly more mothers had amenorrhoea lasting > 180 days among those whose babies spent a longer proportion of the nursing episode in non-sucking pauses > or = 1.5 s. This finding indicates that sensory stimulation of the nipple produced during a nursing episode by stimuli other than sucking itself may have an important role in sustaining lactational amenorrhoea. It is concluded that nursing episodes have a complex structure that allows the development of a breastfeeding phenotype in each mother-baby pair, exhibiting important inter-individual variability. The present analysis does not support the contention that this source of variability accounts for the variability in the duration of lactational amenorrhoea.     

Determinants of breast-feeding and post-partum amenorrhoea in Orissa

A life table analysis is made of the duration of breast-feeding and post-partum amenorrhoea in Orissa, India, taking one variable at a time using data from a baseline survey of fertility and mortality (BSFM) conducted on the lines of the World Fertility Survey. Then a multivariate (proportional hazard) analysis showed that socioeconomic factors including residence, caste status and education influence the breast-feeding and post-partum amenorrhoea periods. There was no effect of maternal age on the length of breast-feeding, but mean length of post-partum amenorrhoea varied with age. The durations of breast-feeding and post-partum amenorrhoea are strongly related.     

Lactational amenorrhoea in well-nourished Toba women of Formosa, Argentina

The proximate causes of the contraceptive effect of lactation are still a matter of productive debate. This study sought to disentangle the relative impact that intense breast-feeding practices and maternal nutrition have on the regulation of ovarian function in nursing women. A mixed-longitudinal, direct-observational, prospective study was conducted of the return to postpartum fecundity in 113 breast-feeding, well-nourished Toba women. A sub-sample of 70 women provided data on nursing behaviour, daily activities, diet quality and urinary levels of oestrone and progesterone metabolites. Well-nourished, intensively breast-feeding Toba women experienced a relatively short period of lactational amenorrhoea (10.2 +/- 4.3 months) and a high lifetime fertility (TFR=6.7 live births/woman). Duration of lactational amenorrhoea was not correlated with any of the nursing parameters under study or with static measures of maternal nutritional status. The results indicated that the pattern of resumption of postpartum fertility could be explained, at least partly, by differences in individual metabolic budgets. Toba women resumed postpartum ovulation after a period of sustained positive energy balance. As the relative metabolic load hypothesis suggests, the variable effect of lactation on postpartum fertility may not depend on the intensity of nursing per se but rather on the energetic stress that lactation represents for the individual mother.     

Effectiveness of lactational amenorrhoea in prevention of pregnancy in Manila,the Philippines: non-comparative prospective trail.

OBJECTIVE: To determine the contraceptive efficacy of the lactational amenorrhoea method. DESIGN: Non-comparative prospective trial. SETTING: Urban Manila, the Philippines. SUBJECTS: 485 lower income, educated women with extensive experience of breast feeding. INTERVENTION: Women were offered all available contraceptives for use after birth. Those who chose the lactational amenorrhoea method were taught the method, screened for the study, and followed for 12 months to determine the risk of pregnancy when the method was used. MAIN OUTCOME MEASURES: Life table pregnancy rates during correct and incorrect use of the method, censored monthly in the event of sexual abstinence or the use of another contraceptive method. RESULTS: The lactational amenorrhoea method was 99% effective when used correctly (that is, during lactational amenorrhoea and full or nearly full breast feeding for up to six months). At 12 months the effectiveness during amenorrhoea dropped to 97%. CONCLUSIONS: The lactational amenorrhoea method provided as much protection from pregnancy as non-breast feeding women experience with non-medicated intrauterine devices and barrier methods. The contraceptive effect of lactation cannot be attributed to lactational or postpartum abstinence.     

Analysis of postpartum lactational amenorrhoea in relation to breast-feeding: some methodological and practical aspects.

A large multicentre epidemiological study was carried out by WHO between 1991 and 1995 to analyse the duration of lactational amenorrhoea in relation to breast-feeding. The main results of this analysis, which used classical statistical modelling, have been already published. However, some specific aspects of the postpartum fertility amenorrhoea and breast-feeding covariates, and more specifically the observed progressive exhaustion of the breast-feeding inhibitory effect on the reproductive axis, may justify a closer look at the validity of the statistical tools. Indeed, as has already been emphasized, analysis of large longitudinal data sets in reproduction often faces three difficulties: (i) the precise determination of the event of interest, (ii) the way to handle the time evolution of both the studied variables and their effect on the event of interest and (iii) the often discrete nature of the data and the associated problem of tied events. The first objective of the present work was to give additional insights into the estimation and quantification of the dynamics of the effect of breast-feeding over time, considering this covariate either as fixed or time-dependent. The second objective was to show how to perform the analyses using corresponding adapted procedures in widely available statistical packages, without the need for acquiring particular programming skills.     

Post-partum events and fertility control in Kinshasa, Za?re

Contraceptive prevalence surveys from sub-Saharan Africa typically show low rates of method use. The current study of one zone in Kinshasa, Za?re, provides a more detailed view of fertility control in an urban population by examining the relative duration of breast-feeding, amenorrhoea and sexual abstinence during the post-partum period. While motivations to prevent pregnancy remain high until the youngest child is over 24 months, the average duration of abstinence is only 4 months. This paper describes the methods women use to avoid pregnancy and the changes over the post-partum period.     

Brief description of WHO protocol for data collection.

WHO Simplified Methodology (1987) is being applied in several studies: the Task Force on Methods for the Natural Regulation of Fertility of the Special Program on Human Reproduction in centers in Chendu, China; Guatemala City, Guatemala; New Delhi, India; Sagamu, Nigeria; Santiago, Chile; Uppsala, Sweden; and Westmead/Sydney, Australia. 550 lactating mothers who can read and write were examined in order to provide a better understanding of the relationship between breast-feeding duration and lactational amenorrhea, and to determine whether the longitudinal study results are applicable to the general population. Protocol involved data collection of breast-feeding frequency, timing, and duration; supplementary feeding characteristics and timing; and maternal and infant health. WHO protocol is also being examined in studies in Colombo, Sri Lanka, and Sagamu, Nigeria. The study objective was to examine the effect of maternal nutritional supplementation with skimmed milk powder in Colombo and a high protein biscuit in Sagamu on the duration of lactational amenorrhea in moderately malnourished breast-feeding mothers. Followup studies are expected. Optimally, the end product should be a measure of the presence of ovulation, however, the logistics prevented this from occurring. Instead, weekly urine samples were collected and tested for the presence of estrogen and pregnanediol glucuronide. Motivation is a key determinant in the success of these projects, since detailed record keeping over a prolonged period of time is required. Motivational interventions vary between centers and may involve social contact with investigators or health care support for the mother and infant. Some preliminary results indicate that the higher the percentage receiving supplementation, the earlier the return of the menses.     

The effect of initiation of child supplementation on resumption of post-partum menstruation

The effects of initiation of solid and liquid supplementation on resumption of post-partum menstruation are examined, using data from a 2-year prospective study of birth interval dynamics from central Java, Indonesia. The sample analysed consisted of 444 women who experienced resumption of menses while breast-feeding, women who were breast-feeding and amenorrhoeic at the end of the study, or women who resumed menstruation or were censored after infant mortality and weaning which preceded the resumption of menses. Multivariate hazard model analysis was used to assess the significance of supplementation, various breast-feeding covariates, and age and parity of the dependent variable. Because the timing of supplementation varies, the supplementation variables were introduced into the analysis as time-varying covariates. For the mothers in the sample, solid and liquid supplementation was initiated at medians of 2.1 and 8.0 months respectively. The former had a significant effect on resumption of menses, while the latter was only marginally significant. Earlier supplementation meant shorter durations of amenorrhoea for the majority of women. However, the effect was not consistent across all categories of women. For the small group of mothers who were low intensity breast-feeders (less than or equal to 6 minutes per nursing episode) or as low frequency day-time breast-feeders (less than or equal to 6 nursing episodes per day-time), earlier supplementation had no additional effect on their rate of resumption of menses post-partum.     

Rate of growth in length of Bangladeshi infants as a function of attained length.

We examine variation in the rate of growth in length of breast-feeding infants from rural Bangladesh. These data were collected between November 1985 and February 1986 from two rural sites. Eighty-eight infants, ranging from birth to 4 months of age at the start of the study and their mothers were measured monthly for 4 months. Length increased linearly with age over this 4-month period (infants' average bias-adjusted R2 = 0.90). The relationship between infant rate of growth in length and attained length was analyzed by two different methods: Oldham's (1962) method of regressing rate of growth on mean length and Blomqvist's (1977) method of regressing rate of growth on estimated initial length. The methods gave similar results. The rate of growth was negatively associated with mean infant length over the 4-month period (p less than 0.001); that is, shorter infants grew at a faster rate than longer infants. For every centimeter shorter the infant was, the rate of growth was 0.1 cm/mo faster on average; the effect was greater among males than among females. The average rate of growth was greater for males than for females and greater in financially solvent households and varied by site. Infant growth rate was slower among older infants than among younger infants, as expected. However, after adjusting for mean infant length, age was no longer significantly associated with infant growth rate, although mean infant length remained highly significant. Forty-one percent of the variation in infant rate of growth in length was explained by mean infant length, sex, sex by length interaction, household financial solvency, and site.     

An investigation into proximate determinants responsible for fertility differentials between two rural Bangladeshi populations

The substantial areal variation in Bangladesh's demographic dynamics is demonstrated by the differential fertility in 2 rural areas--Teknaf, where the total fertility rate is 8.0 and Matlab, where this rate is 6.5 in comparison areas and 5.0 in treatment areas. The fertility differences between the comparison and treatment areas of Matlab are usually attributed to the differential use of contraception, while the fertility difference between Teknaf and Matlab as a whole is assumed to reflect dissimilarities in socioeconomic, environmental, and cultural conditions. Application of a model proposed by Bongaarts which permits analysis of the effects of intermediate variables on fertility reveals similar marital patterns in Teknaf and Matlab but different indexes of infecundability and contraceptive use. Both the comparison and treatment areas of Matlab had 1 birth less than Teknaf because of their high infecundability due to a longer duration of breastfeeding (median duration of 30 months in Matlab compared with 22 months for Teknaf). Contraceptive use contributed 0.51 and 2.36 fewer births in Matlab's comparison and treatment areas, respectively, than in Teknaf. The reasons Teknaf mothers breastfeed their infants for shorter durations than Matlab mothers merit further investigation given the significant contribution of prolonged lactational amenorrhea to lowering fertility. Much of the effect on fertility of the increase in contraceptive use in Matlab's experimental area could not have been achieved if lactation durations were at Teknaf levels, further emphasizing the need for research on breastfeeding behavior in different parts of Bangladesh.     

A biocultural investigation of the weanling's dilemma in Kathmandu, Nepal: do universal recommendations for weaning practices make sense?

The primary objective of this report is to use data from a study of infant growth and weaning practices in Kathmandu, Nepal, to investigate universal recommendations about exclusive breast-feeding up to 6 months postpartum. A secondary objective is to demonstrate the complexity of the biocultural nature of infant feeding practices. A sample of 283 children under 5 years of age and their 228 mothers living in a peri-urban district of Kathmandu participated in this study. The children's height/length and weight were measured three times over 9 months. At each session, a demographic, child health and infant feeding survey was administered; between sessions, in-depth interviews were conducted with mothers regarding infant feeding practices. While a few of the infants under 2 months were receiving non-breast milk foods, at 3 months of age half of the sample had been introduced to non-breast milk foods and by 7 months all infants were eating non-breast milk foods. A comparison of growth indices and velocities between exclusively and partially breast-fed infants from birth to 7 months of age shows no evidence for a difference in nutritional status between the two groups. Although there are cultural rules about breast-feeding that vary by ethnic group, all mothers followed a feeding method that depended on their assessment of whether the child was getting enough breast milk. The conclusion is that exclusive breast-feeding up to 6 months may not be appropriate for all infants. In this sample, breast-feeding duration is not shortened by the early introduction of non-breast milk foods, as the median age of breast-feeding cessation is 36 months. One of the main reasons for severance was the onset of another pregnancy. Investigation of infant feeding practices must be contextualized in the local ecology of the population. While cultural beliefs about breast-feeding are relevant, mothers' individual assessments of their children's nutritional needs and demographic events in parents' lives must also be considered.     

Nursing behaviour and its relation to duration of post-partum amenorrhoea in an Andean community

Nu?oa is a high altitude rural Peruvian community characterized by socioeconomic stratification and differential access to the market economy. Nursing practices and the effects of nursing are also stratified; this translates into a risk of menses at 12 months post-partum nearly seven times greater in wealthier than in poorer women. Most nursing occurs in the morning, among those who practice on-demand breast-feeding. Nursing episodes are clustered into sessions; the amount of breast-feeding is regulated by varying the number of episodes per session rather than by changing the duration of suckling episodes or the frequency of sessions per hour. Thus, resumption of ovulation is not dependent on the variable spacing of nursing episodes or sessions. The components of nursing activity most likely to be responsible for variation in the duration of post-partum amenorrhoea in these nursing women are mean session duration and mean number of episodes per session. The mean duration of morning nursing sessions is negatively associated with infant's age, reflecting the greater reliance of younger children on breast-milk. The mean duration of afternoon nursing sessions is positively associated with mother's age, independent of infant's age, possibly reflecting maternal age-related variation in milk production capabilities. Baby minding by older daughters may also help to explain variation in afternoon nursing.     

Breast-feeding, birth interval and child mortality in Bangladesh

The 1975-76 Bangladesh Fertility Survey data show little evidence that breast-feeding is the intermediate factor through which birth intervals influence child survival in Bangladesh. Preceding birth interval, subsequent pregnancy and breast-feeding duration each have an independent influence on early mortality risk. Within a specific interval the risk of dying decreases with increase in duration of breast-feeding, and also with an increase in the time between the index birth and the next pregnancy. The death of the immediately preceding child in infancy has a significant negative effect on the survival chance of the index child at ages 1-5 months. However, death of the preceding child appears to have a significantly positive effect on the survival chance of the index child between ages 9 months and 5 years; this may be related to competition between siblings.     

The recovery of fertility during breast-feeding in Assiut, Egypt

A longitudinal study of twenty-six breast-feeding and twelve non-breast-feeding postpartum women was conducted in Assiut, Egypt in order to determine the time that ovulation resumed after childbirth, and the effect of breast-feeding frequency on the period of lactational anovulation. Breast-feeding women experienced the onset of follicular development, vaginal bleeding, ovulation and pregnancy significantly later than women who did not breast-feed. Ovulatory and non-ovulatory breast-feeders reported similar frequencies of breast-feeding episodes. The introduction of dietary supplements commonly preceded ovulation. An algorithm using three simple variables observable to the breast-feeding mother was found to predict up to 100% of the first ovulations. All breast-feeding women who did not give supplements and did not have a vaginal bleeding episode by 6 months postpartum were anovular by strict criteria for ovulation. Ovulation did not precede bleeding or supplementation in the women who experienced these events before 6 months, yielding a highly effective formula for preventing unplanned pregnancy by the informed use of breast-feeding.     

Fine needle aspiration of benign and malignant breast masses associated with pregnancy.

Of 1,612 fine needle aspirates (FNA) of breast lesions performed over a seven-year period, 25 cases (1.5%) were identified as breast masses associated with pregnancy. Patients ranged in age from 16 to 46 years, with a mean of 27. Gestational age at the time of FNA ranged from three months to three months postpartum or following breast-feeding. Cytologic diagnoses of these pregnancy-associated breast masses were: galactocele (5 cases, 20%), lactating adenoma (9 cases, 36%), fibroadenoma with lactational change (7 cases, 28%), juvenile fibroadenoma with lactational change (1 case, 4%), atypical reactive duct cells with lactational change (1 case, 4%) and infiltrating duct carcinoma (2 cases, 8%). The degree of lactational change varied proportionately with gestational age. None of the 22 patients with benign cytologic diagnoses of galactocele, lactating adenoma or fibroadenoma subsequently developed carcinoma. The mean clinical follow-up for these 22 patients was 27 months. Three cases of fibroadenoma and the case of juvenile fibroadenoma were confirmed by surgical excision. Biopsy of the lesion cytologically diagnosed as atypical reactive duct cells with lactational change revealed infiltrating duct carcinoma (IDC). All three patients with IDC had involvement of multiple axillary lymph nodes, and 1 patient had widely metastatic disease. In two cases of IDC the background lactational breast epithelium exhibited marked cytologic atypia that closely resembled the IDC. Pregnancy-related cellular atypia potentially results in a false-positive diagnosis of breast carcinoma on FNA. FNA is useful in distinguishing benign breast masses of pregnancy from those with marked cytologic atypia requiring surgical biopsy and may minimize the delayed diagnosis of carcinoma associated with pregnancy.     

The influence of acculturation on breast-feeding initiation and duration in low-income women in the US

While the 'immigrant health paradox' posits better health behaviours and outcomes for immigrants upon arrival to the US, research suggests that this advantage may deteriorate over time. This study analysed the relationship of acculturation and breast-feeding initiation and duration among a sample of predominantly Latina, low-income women in the US. The four measures of acculturation included: mother's nativity (foreign born vs US born), mother's parents' nativity (foreign born vs US born), years of US residence (<8 years vs > or =8 years) and a dichotomous measure of language acculturation adapted from three items on Marin's acculturation scale (preferred language spoken at home, reading language and writing language) as exclusive use of native language versus non-exclusive use (mixed or English only) (Marin et al., 1987; Marin & Gamba, 1996). Final multivariable models showed that mothers who exclusively used their native language were more likely to initiate breast-feeding as well as breast-feed for longer duration compared with mothers with non-exclusive use, whereas years of US residence and mother's nativity were not significantly associated with breast-feeding initiation or duration. Mother's parents' nativity also emerged as a significant predictor of breast-feeding duration, both within final models for immigrants and across study participants. Programmes providing nutrition education to low-income women may wish to consider the role of language as an important determinant of breast-feeding. The role of mother's parents' nativity on breast-feeding practices deserves exploration in future studies, as the cultural practices taught by family members born outside the US may exert strong pressure within immigrant families now living in the US.     

Estimation of births averted due to breast-feeding and increases in levels of contraception needed to substitute for breast-feeding

After contraceptive use, breast-feeding duration is the major determinant of the birth interval length. Three methods of estimating births averted by breast-feeding, and the increase in contraceptive use needed to substitute for breast-feeding, are presented. Method 1 simply utilizes Bongaarts' Ci, and the other two are based on mean birth intervals with and without breast-feeding. Estimates for each method are derived for six countries with DHS surveys from the mid-1990s: Burkina Faso, Uganda, India, Indonesia, Brazil and Peru. The estimated percentage of additional births that would occur if there were no breast-feeding ranged from 1-4%, in Brazil to about 50% in Burkina Faso and Uganda, reflecting very low breast-feeding in Brazil and very high levels in the sub-Saharan African nations. Strengths and limitations of the three methods are considered.     

长、短期连续孤雌生殖对萼花臂尾轮虫生活史和遗传特征的影响

应用单个体培养、聚丙烯酰胺凝胶垂直板电泳技术和特异性染色方法,以具有明显生化遗传差异的3克隆萼花臂尾轮虫（Brachionus calyciflorus）为对象,对长期（世代数大于200）和短期（世代数约为12）连续孤雌生殖后的轮虫进行了生活史特征和等位酶（PGM,GPI,MDH）分析。结果表明,除3克隆轮虫的生殖后期历时和每个雌体一生中所产的后代数在长期和短期连续孤雌生殖后的个体之间均无显著的差异外（P>0.05）,其它生活史特征在长期和短期连续孤雌生殖后的个体之间的差异均因轮虫克隆的不同而异。克隆对轮虫的胚胎发育时间、幼体阶段历时、生殖期历时、平均寿命、轮虫每个雌体一生中所产的后代数、幼体大小和幼体的耐饥饿时间均有显著的影响（P<0.05）;连续孤雌生殖历期对轮虫幼体阶段历时、平均寿命、后代混交雌体百分率和幼体的耐饥饿时间均有显著的影响（P<0.05）;而克隆和连续孤雌生殖历期间的交互作用对轮虫的胚胎发育时间、生殖期历时、平均寿命、幼体大小和幼体的耐饥饿时间均有显著的影响（P<0.05）。长期连续孤雌生殖后的轮虫幼体阶段历时和幼体的耐饥饿时间均显著短于短期连续孤雌生殖后的轮虫,平均寿命显著长于短期连续孤雌生殖后的轮虫,后代混交雌体百分率显著高于短期连续孤雌生殖后的轮虫。3克隆轮虫在长期和短期连续孤雌生殖后其3种等位酶的酶谱均未出现明显的改变。