Influence of breast-feeding pattern on pituitary-ovarian axis of women in an industrialized community

Lactational Amenorrhea: Neuroendocrine Pathways Controlling Fertility and Bone Turnover

Lactation is a physiological state of hyperprolactinemia and associated amenorrhea. Despite the fact that exact mechanisms standing behind the hypothalamus-pituitary-ovarian axis during lactation are still not clear, a general overview of events leading to amenorrhea may be suggested. Suckling remains the most important stimulus maintaining suppressive effect on ovaries after pregnancy. Breastfeeding is accompanied by high levels of prolactin, which remain higher than normal until the frequency and duration of daily suckling decreases and allows normal menstrual function resumption. Hyperprolactinemia induces the suppression of hypothalamic Kiss1 neurons that directly control the pulsatile release of GnRH. Disruption in the pulsatile manner of GnRH secretion results in a strongly decreased frequency of corresponding LH pulses. Inadequate LH secretion and lack of pre-ovulatory surge inhibit the progression of the follicular phase of a menstrual cycle and result in anovulation and amenorrhea. The main consequences of lactational amenorrhea are connected with fertility issues and increased bone turnover. Provided the fulfillment of all the established conditions of its use, the lactational amenorrhea method (LAM) efficiently protects against pregnancy. Because of its accessibility and lack of additional associated costs, LAM might be especially beneficial in low-income, developing countries, where modern contraception is hard to obtain. Breastfeeding alone is not equal to the LAM method, and therefore, it is not enough to successfully protect against conception. That is why LAM promotion should primarily focus on conditions under which its use is safe and effective. More studies on larger study groups should be conducted to determine and confirm the impact of behavioral factors, like suckling parameters, on the LAM efficacy. Lactational bone loss is a physiologic mechanism that enables providing a sufficient amount of calcium to the newborn. Despite the decline in bone mass during breastfeeding, it rebuilds after weaning and is not associated with a postmenopausal decrease in BMD and osteoporosis risk. Therefore, it should be a matter of concern only for lactating women with additional risk factors or with low BMD before pregnancy. The review summarizes the effect that breastfeeding exerts on the hypothalamus-pituitary axis as well as fertility and bone turnover aspects of lactational amenorrhea. We discuss the possibility of the use of lactation as contraception, along with this method's prevalence, efficacy, and influencing factors. We also review the literature on the topic of lactational bone loss: its mechanism, severity, and persistence throughout life.

Factors affecting breastfeeding duration in Greece: What is important?

AIM: To investigate factors associated with breastfeeding duration (BD) in a sample of mothers living in Greece.

METHODS: Four hundred and twenty-eight mothers (438 infants) were initially recruited in a tertiary University Hospital. Monthly telephone interviews (1665 in total) using a structured questionnaire (one for each infant) were conducted until the sixth postpartum month. Cox regression analysis was used to assess factors influencing any BD.

RESULTS: Any breastfeeding rates in the first, third, and sixth month of the infant’s life reached 87.5%, 57.0% and 38.75%, respectively. In the multivariate analysis, maternal smoking in the lactation period [hazard-ratio (HR) = 4.20] and psychological status (HR = 1.72), and the introduction of a pacifier (HR = 2.08), were inversely associated, while higher maternal education (HR_{university/collegevsprimary/high school} = 0.53, HR_{master’svsprimary/high school} = 0.20), and being an immigrant (HR = 0.35) were positively associated with BD.

CONCLUSION: Public health interventions should focus on campaigns against smoking during lactation, target women of lower educational status, and endorse the delayed introduction of pacifiers.

Breastfeeding and maternal health outcomes: a systematic review and meta-analysis

AIM

To evaluate the effect of breastfeeding on long-term (breast carcinoma, ovarian carcinoma, osteoporosis and type 2 diabetes mellitus) and short-term (lactational amenorrhoea, postpartum depression, postpartum weight change) maternal health outcomes.

METHODS

A systematic literature search was conducted in PubMed, Cochrane Library and CABI databases. Outcome estimates of odds ratios or relative risks or standardised mean differences were pooled. In cases of heterogeneity, subgroup analysis and meta-regression were explored.

RESULTS

Breastfeeding >12 months was associated with reduced risk of breast and ovarian carcinoma by 26% and 37%, respectively. No conclusive evidence of an association between breastfeeding and bone mineral density was found. Breastfeeding was associated with 32% lower risk of type 2 diabetes. Exclusive breastfeeding and predominant breastfeeding were associated with longer duration of amenorrhoea. Shorter duration of breastfeeding was associated with higher risk of postpartum depression. Evidence suggesting an association of breastfeeding with postpartum weight change was lacking.

CONCLUSION

This review supports the hypothesis that breastfeeding is protective against breast and ovarian carcinoma, and exclusive breastfeeding and predominant breastfeeding increase the duration of lactational amenorrhoea. There is evidence that breastfeeding reduces the risk of type 2 diabetes. However, an association between breastfeeding and bone mineral density or maternal depression or postpartum weight change was not evident.

Dioxin exposure blocks lactation through a direct effect on mammary epithelial cells mediated by the aryl hydrocarbon receptor repressor

In mammals, lactation is a rich source of nutrients and antibodies for newborn animals. However, millions of mothers each year experience an inability to breastfeed. Exposure to several environmental toxicants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has been strongly implicated in impaired mammary differentiation and lactation. TCDD and related polyhalogenated aromatic hydrocarbons are widespread industrial pollutants that activate the aryl hydrocarbon receptor (AHR). Despite many epidemiological and animal studies, the molecular mechanism through which AHR signaling blocks lactation remains unclear. We employed in vitro models of mammary differentiation to recapitulate lactogenesis in the presence of toxicants. We demonstrate AHR agonists directly block milk production in isolated mammary epithelial cells. Moreover, we define a novel role for the aryl hydrocarbon receptor repressor (AHRR) in mediating this response. Our mechanistic studies suggest AHRR is sufficient to block transcription of the milk gene β-casein. As TCDD is a prevalent environmental pollutant that affects women worldwide, our results have important public health implications for newborn nutrition.

Nutritional requirements during lactation. Towards European alignment of reference values: the EURRECA network

There is considerable variation in reference values for micronutrient intake during lactation across Europe. The European Micronutrients Recommendations Aligned project aims to harmonize dietary recommendations throughout Europe. Recommended nutrient intakes during lactation are based on limited data and are often extrapolated from known secretion of the nutrient in milk with adjustments for bioavailability, so that differences between values can be partly ascribed to differences in methodological approaches and how these approaches were applied. Few studies have considered the impact of lactation on the mother's nutritional status. Rather, focus has been placed on the influence of maternal nutritional status on the composition of her breast milk. Most common nutritional deficits in breast milk are the result of maternal deficiencies of the water-soluble vitamins, thiamine, riboflavin and vitamins B6 and B12. Other than maternal vitamin A status, which to some extent is reflected in breast milk, concentrations of fat-soluble vitamins and most minerals in breast milk are less affected by maternal status. Factors relating to suboptimal maternal nutritional status during lactation include maternal age, diet and lifestyle factors and spacing of consecutive births. Recent research is providing new knowledge on the micronutrient requirements of lactating women. Identifying needs for research and improving understanding of the differences in values that have been derived by various committees and groups across Europe will enhance transparency and facilitate the application of dietary recommendations in policy-making decision and their translation into recommendations for lactating women. Given the wide variation in breastfeeding practices across Europe, making nutritional recommendations for lactating women is complex and challenging. Thus, it is crucial to first examine the cultural practices within and across European populations and to assess its relevance before making recommendations.

Prenatal exposure to passive smoking and duration of breastfeeding in nonsmoking women: Krakow inner city prospective cohort study

INTRODUCTION

The relationship between tobacco smoking in pregnancy and breastfeeding is of public health importance. The present birth cohort study provided the opportunity to investigate whether the negative relationship between passive smoking measured by the cotinine concentrations in maternal blood at delivery and breastfeeding in postpartum could also be confirmed in nonsmoking mothers.

MATERIALS AND METHODS

The study sample included 441 healthy pregnant women who were recruited in the first and second trimester of pregnancy. Enrollment included only nonsmoking women of the age of 18-35 years with singleton pregnancies, without illicit drug use and free from chronic diseases. After delivery, breastfeeding duration was defined using the answers recorded in the interviews with mothers conducted every 3 months. An infant was considered to be fully breastfed when breast milk was the only source of nourishment. Any breastfeeding was defined as an infant's being fully breastfed or receiving both breast milk and formula, with or without solids. In the statistical analysis only total duration of breastfeeding up to 6 months was considered for both forms of breastfeeding. Subjects were categorized into environmental tobacco smoke (ETS) exposure groups according to maternal blood cotinine level at delivery or self-reported exposure to ETS during pregnancy.

RESULTS

The adjusted relative risk of discontinuation of any breastfeeding after infant's first 6 months was more than two times higher (OR = 2.42; 95% CI: 1.42-4.14) in women whose blood cotinine level at delivery was above 75th percentile of cotinine distribution (>0.15 ng/mL); the corresponding risk of discontinuation of full breastfeeding was OR = 1.71; 95% CI: 1.03-2.82. Estimated relative risk of discontinuation of any breastfeeding based on self-reported ETS was also significant but much less marked; the corresponding risk of discontinuation of full breastfeeding was insignificant.

CONCLUSION

The results obtained support the hypothesis that ETS may affect breastfeeding duration and support the avoidance of passive smoking as a necessary additional measure for breastfeeding promotion.

Maternal smoking and reduced duration of breastfeeding: a review of possible mechanisms

AIM

To systematically review the possible mechanisms by which maternal smoking affects lactation.

METHODS

Databases (Medline, CINAHL, Current Contents, Psychinfo, Sociological Abstracts and the Cochrane Library) were searched for smoking and breastfeeding or infant feeding. The Journal of Human Lactation and Birth were hand-searched, searches were also conducted at NMAA's Lactation Resource Centre and references cited were located where appropriate. Articles were divided into the various ways that smoking could affect breastfeeding and were tabulated.

RESULTS

Most studies were conducted on small samples of animals or humans; the majority were prior to 1985. Most animal studies exposed the animals to much greater levels of nicotine than those to which humans are exposed. Most studies did not examine if breastfeeding behaviour was similar in smokers and non-smokers, and did not consider that any physiological difference found could be the result of poor lactation practices, rather than the cause of poor lactation in smokers. The definition of breastfeeding infants was also problematic in many studies. The effect of smoking on oxytocin in women was only examined in one study, and no effect was found, yet a negative effect of smoking on oxytocin release is reported in the breastfeeding literature.

CONCLUSION

Although there is consistent evidence that women who smoke breastfeed their infants for a shorter duration than non-smokers, the evidence for a physiological mechanism is not strong.

Intention to use the female condom following a mass-marketing campaign in Lusaka, Zambia

OBJECTIVES

This report examines intention to use the female condom among men and women in Lusaka, Zambia, who were exposed to mass-marketing of the female condom.

METHODS

The study used data from a representative sample of consumers at outlets that sell or distribute the female condom and the male condom.

RESULTS

In spite of a high level of awareness of the female condom, use of this method in the last year was considerably lower than use of the male condom. Intention to use the female condom in the future was highest among respondents who had used only the female condom in the last year.

CONCLUSIONS

The female condom is likely to be most important for persons who are unable or unwilling to use the male condom.

Maternal smoking and the risk of early weaning: a meta-analysis

OBJECTIVES

This study reviewed evidence on the effect of maternal smoking on early weaning.

METHODS

The following databases and journals were searched: Medline, Scientific Citation Index, Pediatrics, Journal of Pediatrics, New England Journal of Medicine, and Lancet. Analysis was restricted to studies in which infants who had never been breastfed were excluded or the prevalence of breastfeeding initiation was more than 90%.

RESULTS

In smoking vs nonsmoking mothers, the random effects odds ratio for weaning before 3 months was 1.93 (95% confidence interval [CI] = 1.55, 2.40). An adjusted odds ratio of 1.50 (95% CI = 1.34, 1.68) was shown in studies that had lost-to-follow-up rates below 15% and included adequate adjustment for confounding.

CONCLUSIONS

Maternal smoking increases the risk of early weaning.

Smoking relapse and early weaning among postpartum women: is there an association?

BACKGROUND

Smoking in the postpartum period may contribute to early weaning, although the nature and temporal aspect of the relationship are poorly understood. The objective of this study was to examine the association between early weaning and smoking relapse among women who stopped smoking during pregnancy.

METHODS

A secondary analysis of data from a randomized controlled trial was conducted. The participants were 228 women who had stopped smoking for pregnancy, who participated in a smoking relapse prevention trial, and who breastfed. Women who relapsed to daily smoking postpartum were compared with those who remained abstinent or smoked occasionally. The dependent variable was breastfeeding for less than 26 weeks (early weaning). Potential covariates included intended duration of breastfeeding, parity, partner's smoking, nicotine dependence, emotional health, return to paid employment, and various sociodemographic variables.

RESULTS

Approximately two-thirds (65.1%) of the women who relapsed to daily smoking weaned before 26 weeks compared with 33.8 percent of the women who remained abstinent or smoked occasionally. Controlling for intended duration of breastfeeding, education, and return to paid employment, women who resumed daily smoking were almost four times more likely to wean early than those who abstained or smoked occasionally.

CONCLUSIONS

Early weaning may result from psychological or physiological changes associated with tobacco use. Smoking relapse prevention in the postpartum period may be one of the most effective interventions in ensuring that women who stop smoking for pregnancy remain stopped and breastfeed their babies for the recommended duration.

The World Health Organization Multinational Study of Breast-feeding and Lactational Amenorrhea. II. Factors associated with the length of amenorrhea. World Health Organization Task Force on Methods for the Natural Regulation of Fertility

OBJECTIVE

To determine the relation between infant feeding practices (and other factors) and the duration of postpartum amenorrhea, and to establish whether there are real differences in the duration of postpartum amenorrhea for similar breast-feeding practices in different populations.

DESIGN

Prospective, nonexperimental, longitudinal follow-up study.

SETTING

Five developing and two developed countries.

PATIENT(S)

Four thousand one hundred eighteen breast-feeding mothers and their infants.

INTERVENTION(S)

Breast-feeding women collected ongoing information about infant feeding and family planning practices, plus the return of menses. Fortnightly follow-up occurred in the women's homes.

MAIN OUTCOME MEASURE(S)

A multivariate analysis explored the association between the risk of menses return and 16 infant feeding variables and 11 other characteristics.

RESULT(S)

Ten factors (in addition to center effects) were significantly related to the duration of amenorrhea. Seven of these were infant feeding characteristics and the remaining three were high parity, low body mass index, and a higher frequency of infant illness.

CONCLUSION(S)

The breast-feeding stimulus is strongly linked to the duration of postpartum amenorrhea. Cross-cultural effects also are extremely important and may have caused the variations in feeding, the variation in amenorrhea, or both.

The World Health Organization Multinational Study of Breast-feeding and Lactational Amenorrhea. I. Description of infant feeding patterns and of the return of menses. World Health Organization Task Force on Methods for the Natural Regulation of Fertility

OBJECTIVE

To detect differences between populations in both infant feeding practices and the duration of lactational amenorrhea, if they exist.

DESIGN

Prospective, nonexperimental, longitudinal follow-up study.

SETTING

Five developing and two developed countries.

PATIENT(S)

Four thousand one hundred eighteen breast-feeding mothers and their infants.

INTERVENTION(S)

Breast-feeding women collected ongoing information about infant feeding and family planning practices, plus the return of menses. Fortnightly follow-up occurred in the women's homes.

MAIN OUTCOME MEASURE(S)

Breast-feeding frequency by day (and by night); 24-hour breast-feeding duration, percent of all infant feedings that were milk/milk-based (and solid/semisolid foods); time until the end of full breast-feeding; time until regular supplementation; and time until the end of lactational amenorrhea.

RESULT(S)

Differences between the centers in the duration of amenorrhea were substantial, ranging from a median of 4 months in New Delhi (India) to 9 months in Chengdu (China). Women in developed countries (but also women in Chengdu) were more likely to delay supplementation (for up to 5 months), whereas women in Santiago (Chile), Guatemala City (Guatemala), and Sagamu (Nigeria) started supplements much earlier, sometimes as early as 1 week after birth.

CONCLUSION(S)

Both breast-feeding behavior and the duration of lactational amenorrhea vary markedly across settings, indicating that breast-feeding promotion and family planning advice should be site- and culture-specific.

Lactation and fertility

Breastfeeding suppresses ovarian activity resulting in amenorrhea and infertility. The frequency of breastfeeds and their duration appear to be important in maintaining amenorrhea--and night-time sucking appears to be particularly crucial. Supplementary feeding may affect fertility by altering suckling behaviour, but the evidence is confusing as to whether feeding supplements reduces the duration of amenorrhea and increases the risk of conception. Mothers who are better nourished tend to have a shorter period of amenorrhea than the malnourished, possibly because the infant has to suckle for a shorter period to obtain the nourishment needed. Lactation has an important effect on fertility at the population level. However, it cannot be considered a reliable contraceptive at an individual level.

The feasibility of suppressing ovarian activity following the end of amenorrhoea by increasing the frequency of suckling

OBJECTIVE

To determine the feasibility of suppressing ovarian activity by increasing the frequency of suckling episodes.

METHOD

Prospective study was carried out with 19 exclusively breastfeeding volunteers. Ten subjects (experimental group) increased the suckling episodes by minimum 50% per day from the beginning of the first postpartum menses. Nine controls continued breastfeeding as before. Estradiol, progesterone, LH, FSH and prolactin were measured in blood samples, drawn twice a week up to the second postpartum menses or for 60 days, by RIA. Student's t-test was employed.

RESULT

The higher suckling frequency prevented ovulation in 7 of 10 cases examined according to the plasma progesterone concentration (< 9.5 nmol/l). Significantly higher average prolactin value could also be found in the experimental group (1038 (527) munits/l vs. 518 (245) munits/l; P < 0.05).

CONCLUSION

Results suggest that an earlier initiation of the increase in breastfeeding frequency may delay the resumption of ovulation. Frequent, full time lactation may reduce the risk of pregnancy.

Smoking and breastfeeding: an overview

This paper reviews what is presently known about the associations between cigarette smoking, breastfeeding and infant health. Smoking almost certainly reduces lactational capacity. Tobacco constituents and combustion by-products reaching the infant through breastmilk or by inhalation are cause for concern. But artificially-fed infants are similarly exposed to many such compounds, and they in addition are at greater risk of respiratory and gastrointestinal disease, allergic disorders, and cot death. Hence breastfeeding must continue to be encouraged, even for smoking mothers. Recommendations that may reduce infant morbidity from smoking by the breastfeeding mother are set out. The author concludes that the scientific literature indicates that it is far from ideal to smoke and breastfeed--but it is worse to smoke and not breastfeed.

The effect of ergometrine on breast feeding

A randomised, controlled trial of 1429 women was carried out to compare 'active' management of the third stage of labour, using i.v. Ergometrine 0.5 mgs, with a method of 'physiological' management, in women at 'low risk' to haemorrhage. A separate sub-study, with 168 women in each of the two groups, examined the possible effects of Ergometrine on serum prolactin levels and the duration of breast feeding. No difference was found in peak (post-suckling) serum prolactin levels taken from 126 women between 48 and 72 hours postnatal. Further studies with larger sample sizes would give a more dependable result. Women who did not receive the drug Ergometrine were more likely to continue breast feeding for longer than four weeks than those who did (p less than 0.05). It is recommended that this drug should not be given routinely to women intending to breast feed.

The antiestrogenic effect of cigarette smoking in women

Epidemiologic results indicate that women who smoke cigarettes are relatively estrogen-deficient. Smokers have an early natural menopause, a lowered risk of cancer of the endometrium, and an increased risk of some osteoporotic fractures. Moreover, women who smoke may have a reduced risk of uterine fibroids, endometriosis, hyperemesis gravidarum, and benign breast disease. Several possible mechanisms for these effects have been identified. Smoking does not appear to be clearly related to estradiol levels, at least in postmenopausal women, although levels of adrenal androgens are increased. Moreover, smoking appears to alter the metabolism of estradiol, leading to enhanced formation of the inactive catechol estrogens.

Risk of ovulation during lactation

60 breastfeeding mothers in Baltimore and 41 in Manila recorded their infant feeding patterns daily, and gave additional information at weekly interviews. Ovarian activity was monitored by assays for hormone metabolites in daily urine samples. On average, women in Baltimore breastfed less often but for longer at each feed than women in Manila, and the mean times until ovulation were 27 and 38 weeks post partum. 41% of first ovulations had luteal phase defects. Anovular first menses were common (45.1%) during the first 6 months post partum but the rate fell greatly thereafter. The risk of ovulation was reduced by a higher frequency of breastfeeds, longer duration of each feed, and less supplementary feeding. During the first 6 months post partum, amenorrhoeic women had low risks of ovulation (below 10%) with partial breastfeeding, and exclusive breastfeeding reduced the risk to 1-5% with either frequent short feeds or infrequent longer feeds. However, if the woman started menstruating before 6 months post partum, or if she continued breastfeeding beyond 6 months, the risk of ovulation rose, and contraception would be needed.

A study of breastfeeding and the return of menses and pregnancy in Karachi, Pakistan

A longitudinal study of breastfeeding women was conducted to determine whether breastfeeding frequency is associated with the length of postpartum amenorrhea. The data are also conducive to testing the guidelines of the "Bellagio Consensus" (i.e., that there is no more than a 2% chance of pregnancy during breastfeeding in the first six months postpartum in the absence of vaginal bleeding and regular supplements). Twenty-eight breastfeeding women were followed-up weekly in Karachi, Pakistan. The frequency of breastfeeding was found to be a poor correlate of the duration of amenorrhea. Thirty-six percent of the women became pregnant during the study. However, all were having menses and/or giving regular supplements before the estimated date of conception, consistent with the Bellagio Consensus. In countries such as Pakistan, where contraceptive use is low, active promotion is needed to prevent the further decline of breastfeeding in order to retain its contraceptive as well as other maternal and child health benefits.

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

Nuñoa 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.

The use of breastfeeding as a contraceptive

Breastfeeding generally is considered an ineffective method of birth control. Yet, in non-Western cultures breastfeeding has been shown to be a beneficial method for spacing births. The physiological effect of breastfeeding on ovulation, breastfeeding patterns that delay the return of ovulatory activity, and the practice of fertility awareness during the postpartum period are reviewed. Guidelines are suggested for assessing, teaching, and referring women desiring to use breastfeeding as a contraceptive method.

Lactational amenorrhea and the recovery of ovulation and fertility in fully nursing Chilean women

The probability of experiencing the first postpartum bleeding, the first ovulation and the risk of pregnancy during exclusive breastfeeding was assessed in a selected group of urban Chilean women. Admission criteria included having had a normal pregnancy and a vaginal term delivery of a healthy infant and the desire to maintain breastfeeding for as long as possible. The risk of bleeding and the recovery of ovulation was assessed in 48 women selected for being amenorrheic and fully nursing at day 75 postpartum and their willingness to participate in the blood sampling protocol. The first bleeding and ovulation was experienced while fully nursing by 28% and 26% of these subjects, respectively, at day 180 postpartum. The probability of experiencing the first bleeding and the probability of pregnancy during full nursing were calculated for 236 women not contracepting who were enrolled during the first month postpartum. The cumulative probability of bleeding and of pregnancy was 52% and 9.4% at day 180 postpartum, respectively. The risk of pregnancy was less than 2% in the subset of amenorrheic cases. In this urban population selected for having the highest motivation and best breastfeeding performance, the association of breastfeeding with infertility was too weak to serve as an effective birth spacer, except for the period of lactational amenorrhea. When the first postpartum bleeding took place before the sixth postpartum month in fully nursing women, it had a good predictive value to indicate the onset of a higher risk period.

A study on the feasibility of suppressing ovarian activity following the end of postpartum amenorrhoea by increasing the frequency of suckling

The aim of the study was to test the effect of increasing the frequency of breastfeeding upon ovarian function following the end of postpartum amenorrhoea. Women exclusively breastfeeding (n = 14) who experienced their first postpartum menstruation between the third and fifth month after delivery were randomly allocated to an experimental (n = 7) and a control (n = 7) group and studied during the next two cycles. Women in the experimental group agreed to increase the number of breastfeeding episodes per day throughout the second cycle. Blood samples were drawn twice a week from the first to the third postpartum menstruation for prolactin, oestradiol and progesterone determinations. The number of breastfeeding episodes per day and night and the length of each episode were recorded daily. An average frequency of 11 nursing episodes per 24 h was reported during the first study cycle in both groups. The experimental group increased by 50% the breastfeeding frequency after the second menstruation while the control group kept its spontaneous feeding pattern. The increase of suckling frequency occurred mainly during day hours. The total breastfeeding time per 24 h was not increased. The length of the menstrual cycle was not altered by the increased suckling frequency. The endocrine pattern differed neither between the first and second cycle of the experimental group nor between the experimental and control group, with the exception of PRL levels which were higher in the experimental group throughout both cycles. Twenty cycles (71%) showed progesterone values compatible with ovulation (greater than 9.5 nmol/l). The highest progesterone values and the highest oestradiol values observed in the ovulatory cycles of lactating women were within the range found in non-nursing fertile women. Plasma levels of PRL were significantly elevated in all cycles but one, in comparison with PRL levels in non-nursing women. It is concluded that if cyclic ovarian function is reestablished early in fully nursing women, a mere increase in the number of breastfeeding episodes, without augmenting total suckling time and the frequency of nocturnal episodes, does not provide a sufficient stimulus to resuppress the pituitary-ovarian axis.

Suckling patterns and post-partum amenorrhea in Bangladesh

The association between breast-feeding patterns and resumption of menses post-partum was examined in a longitudinal study initiated in March 1976 in Bangladesh. Information on suckling patterns and menstrual status was collected on 148 breast-feeding women who were still amenorrhoeic at 17–25 months post-partum at the beginning of the study. Suckling was measured during an 8-hr period once a month for up to 19 months of follow-up.

A high frequency of suckling was found, even at this late post-partum duration. Total suckling time and the number of suckling episodes declined with the age of the child but the mean duration of each episode did not change. The fact that regression analyses did not show a correlation between suckling patterns and return of menses post-partum may be related to the large individual variations in suckling patterns and in the duration of amenorrhoea in this population, and the need to study suckling patterns for longer than 8 hr per day.

Nursing behaviour, prolactin and postpartum amenorrhoea during prolonged lactation in American and !Kung mothers

In order to determine the effects of protracted nursing in American women, blood was collected hourly for 24 h and nursing periods recorded in 20 mothers, 10 amenorrhoeic, 3 3/4 to 17 1/4 months postpartum (PP), and 10 menstruating, 5 1/4 to 46 months PP. These data were compared to the daytime nursing behaviour and 1000-1100 h PRL of women among !Kung hunter-gatherers of Botswana, a non-contraceptive using population with a birth space interval of greater than 3 years. Intense nursing behaviour maintained amenorrhoea and hyperprolactinaemia for 1 to nearly 2 years PP in both American and !Kung mothers. Among Americans, 80 min of nursing per day, in conjunction with a minimum of six nursing episodes, was highly predictive of remaining amenorrhoeic up to 18 months PP. Amenorrhoea was always accompanied by hyperprolactinaemia, but delay in the onset of menses was related more to nursing behaviour than to a particular 24 h PRL level. The 1000-1100 h sample is equivalent to and about half of the 24 h mean in high and low intensity nursers, respectively. The !Kung women were similar to the high intensity nursing American women in 1000-1100 h PRL, percent amenorrhoeic, and the number of minutes of daytime nursing.

Cigarette smoking by pregnant women with particular reference to their past and subsequent breast feeding behaviour

1,790 postpartum women were asked about their smoking habits and baby feeding practices and about a number of other attitudes and physical attributes. For those variables not concerned with baby feeding, our findings generally support previous research; for example, smokers in comparison to non-smokers tended to have more emotional problems, more reproductive failures and babies with lower birth-weights. For baby feeding, we found that smokers tended to have little prior knowledge of breast feeding, favour bottle feeding, have been fed by bottle by their mothers, and wean earlier than non-smokers or ex-smokers. In fact, non-smokers as a group were similar to breast feeders as a group, and smokers like bottle feeders for over 20 characteristics. These similarities were mostly the result of features of smoking and baby feeding behaviour being found in a common personality type; for example, use of tobacco and choice of bottle feeding are probably attributes of nervous, insecure mothers. But some similarities were the result of the influence of tobacco smoke; for example smokers who do breast feed wean earlier, probably because chemicals in tobacco smoke inhibit milk production.

The prolactin response to suckling

Changes in prolactin concentration during single suckling episodes in twenty breast-feeding women from four to 40 weeks post partum have been investigated. Basal prolactin concentration and the increase in prolactin secretion in response to single suckling episodes and amount of milk taken by the infant were both independent of time post partum until the introduction of supplementary feeds, when a significant decrease with time was apparent. Basal concentrations of prolactin were dependent upon the interval between suckling episodes, and the magnitude of the prolactin response varied with the time of day when suckling took place. The relationship between acute suckling episodes and the long term pattern of prolactin secretion over time post partum is discussed.

Fertility after childbirth: pregnancy associated with breast feeding

During studies on the resumption of fertility postpartum in 12 breast feeding mothers who were using no contraception, eight pregnancies occurred. In seven cases these pregnancies occurred while the mothers continued to breast feed while in one it occurred within 2 weeks of weaning. In two cases pregnancy occurred prior to first postpartum menstruation but followed an abrupt decline in suckling frequency and duration resulting in resumption of follicular development and ovulation. In the remaining six cases, pregnancy was preceded by between 1 and 7 menstrual cycles, the majority of which (13/19) had deficient luteal phases or were anovular (4/19). In all mothers a significant decrease in the suckling frequency and duration observed during lactational amenorrhoea had occurred prior to the resumption of ovulation and conception. No mother conceived with a suckling frequency of greater than three times per day although some mothers ovulated without conceiving when suckling four times per day. The results suggests that if a breast feeding mother wishes to rely upon the infertility associated with lactational amenorrhoea, she must suckle at least five times per day with a total suckling duration of more than 65 min per day (more than 10 min per feed). Any reduction below either of these limits may result in a return of fertility.