Effects of parity on breastfeeding: a study in the rural setting in northern Thailand.

UNLABELLED: This analysis was undertaken to see whether or not previous successful breastfeeding has any influence on subsequent breastfeeding behavior. Lactational outcomes were compared between those with and without breastfeeding experience. METHODS: Amount of breast milk transferred, frequency of breastfeeding, and time spent on the breast, as well as infant's weight, were recorded on days 15, 45, 90, 180, 270, and 360 postpartum in 30 primiparae and 30 multiparae. Outcomes of the primiparae were found to be similar to those of the more experienced breastfeeding multiparous mothers with respect to infant growth, amount of breast milk transferred, and the frequency of breastfeeding or number of attachments to the breast. Though primiparae took somewhat longer to transfer similar amounts of breast milk to their infants during the initial 45 to 90 days postpartum, feed duration after 90 days was similar to that of the multiparae. Lactation performance of the rural northern Thai mothers in our sample was highly successful with or without previous breastfeeding experience. It may be that a cultural pattern of breastfeeding on demand, strong family support, and traditional practices that encourage close contact between mother and her newborn compensate for the absence of lactational experience. Unlike reports from Western countries, previous breastfeeding does not appear to be an important predictor of successful and prolonged breastfeeding in our population.

Energy intake, appetite and body mass in infancy.

Energy intake in infancy depends on the infant's appetite, which, in turn, depends to a considerable extent on the infant's size, as size is an important determinant of energy expenditure. Previous work on six-week old breast-fed infants has suggested that, at this age, milk intake in infants is proportional to the square root of body weight (wt.(0.5)). In this paper, the form of the relationship between body weight and energy intake is examined in infants of different ages, using data from two longitudinal studies, one of initially breast-fed and one of initially bottle-fed infants. In the first data set, energy intake is proportional to body weight raised to powers ranging from 0.63 to 1.23 at different ages and, in the second, to body weight raised to powers ranging from 0.50 to 1.07 at different ages. No single value is consistent with all the data at all ages. In general, the powers decrease up to six months of age, and then increase again, a pattern that may be due to the pattern of changes in the adiposity of the infants, as reflected in their body mass indexes (BMIs).

Maternal behaviour and socio-economic influences on the bacterial content of infant weaning foods in rural northern Thailand.

The bacterial contamination of infant weaning foods was examined in the context of a longitudinal study of lactation and infant growth, the Chiang Mai Lactation Study. Sixty-two mother-infant pairs were selected by random sampling from a rural area outside the city of Chiang Mai and studied for 48 hours in their homes on six occasions over the first year of life. Data on food hygiene practices and maternal factors were related to the total bacterial count per gram and coliform content of weaning foods. Bottle feeding, premastication, and mashing were significantly related to an increased bacterial content of weaning foods, while boiling foods to make soups, preparing in and feeding from a banana leaf, and using boiled water to prepare foods all reduced their bacterial content. Storage also increased the bacterial contamination in foods and foods were more highly contaminated in the rainy season. Maternal age and education were also related to some feeding practices. By promoting the feeding of traditional, but less contaminated weaning foods, an intervention is put forward which would aim to reduce weaning food contamination and thereby reduce incidence of diarrhoea in this area of Northern Thailand.

The effect of oral contraceptives on protein metabolism.

The effect on protein and amino acid metabolism of combined oral contraceptives (OC) containing 150 micrograms of laevonorgestrel and 30 micrograms of ethinyl oestradiol was studied in a group of 34 healthy non-lactating women. This was compared to an identical study conducted in another group of 19 subjects who used IUCDs for contraception, and also in two other groups of subjects who were given an additional multivitamin preparation on a daily basis (29 subjects) and on the days when OC was not taken (29 subjects). Assessments were made prior to, and during the third week of the 4th, 7th, and the 13th cycles of OC treatment. Results indicated that the ceruloplasmin and retinol binding protein underwent significant increases with OC usage, while sex hormone binding globulin concentration, on the other hand, remained unaffected. At the same time, a significant reduction of several of the plasma amino acid and plasma albumin concentrations was observed, suggesting that the increase in the visceral and other types of protein concentrations previously noted was due to increased hepatic protein synthesis rather than increased breakdown or excretion as result of OC intake. Interesting biochemical alterations and metabolic effects previously observed may well be related to this altered synthesis and release of proteins and/or protein binders as well as induction of certain metabolic enzymes from the liver.

PIP: To assess the effects of combined oral contraceptive (OC) use on protein and amino acid metabolism, measurements were obtained from four groups of women: Group 1 (29 women who took OCs for 21 days followed by 7 days of multivitamin administration); Group 2 (29 women who took OCs and multivitamins concurrently for 21 days); Group 3 (34 women who took OCs and a placebo for 21 days); and Group 4 (19 IUD users). The OC used in this study contained 30 mcg of ethinyl estradiol and 150 mcg of levonorgestrel; 13 cycles were evaluated in the one-year study period. The fasting concentrations of ceruloplasmin and retinol binding protein increased by an average of 155% and 178%, respectively, above baseline in OC users but not in IUD controls. Fasting plasma concentrations of sex hormone binding globulin showed no changes over baseline in any of the four groups. Free amino acid concentrations were depressed in OC users by 13-33%, with the largest decreases occurring for tyrosine, glycine, ornithine, and proline. Finally, mean concentrations of alpha-1 and beta-globulins increased in OC users, while albumin and total protein decreased significantly. Overall, there was a trend toward increased hepatic protein synthesis with a resultant reduction in concentrations of plasma amino acids and albumin. Multivitamin supplementation did not alter any of these patterns.

A direct radioimmunoassay for free progesterone in saliva.

The direct radioimmunoassay using iodinated tracer (125I-HIS-3CMO) has been developed for the determination of salivary progesterone of healthy volunteers with regular menstrual cycles. Lack of significant diurnal variation either in the follicular or luteal phase indicated that collections of saliva could be tailored to the need of individuals making the study somewhat easier. Salivary progesterone has shown to correlate significantly with free serum progesterone reflecting the unbound biologically active progesterone fraction in blood. Moreover, salivary progesterone concentration ranges are similar to those found in other studies. Our findings indicated that determination of progesterone in saliva could be used in place of serum or plasma. Since firstly, it is non-invasive, easy for sample collection and a stress-free technique. Secondly, it is much more accurate in prediction of corpus luteum function and ovulation than the basal-body temperature or endometrial biopsy or other clinical predictors currently in use. Finally, determination of daily salivary progesterone levels throughout the menstrual cycle may be advantageously employed as a non-invasive serial sampling technique for the assessment of corpus luteum and ovarian functions.

Nursing frequency and the energy intake from breast milk and supplementary food in a rural Thai population: a longitudinal study.

A group of 60 infants representative of a rural Thai population were studied longitudinally over the first year of life. Their breast milk intake, supplementary food intake and nursing patterns were measured for 2 consecutive days at about 15, 45, 90, 180, 270 and 360 days of age. For the sample as a whole, the estimated peak value for energy intake from breast milk was 529 kcal (2213 kJ) and occurred at 34 days post-partum. Thereafter milk intake declined, with 40% of infants fully weaned by the end of the first year. Supplements were introduced early, with 15% of infants supplemented by 2 weeks and 68% by 6 weeks. Higher levels of supplementation were associated with lower breast milk intake. In addition there was an independent positive effect of nursing patterns (number of breast feeds per day). Interaction terms show that both supplementary feeding and number of feeds have quantitatively different effects at different ages: breast milk intake varies more with level of supplementation in younger infants than in older infants, and varies more with number of feeds in older infants than in younger infants. Higher peak levels of breast milk intake were followed by a steeper decline, and infants who took more breast milk at 15 days were more likely to be fully weaned by their first birthday.

Weaning practices and breast-feeding duration in Northern Thailand.

Current infant feeding guidelines recommend exclusive breast-feeding until the infant is about 4 months old to reduce the risks of early termination of breast-feeding, undernutrition and infection. In many societies, however, supplementary foods are given well before 4 months of age. The present paper describes weaning practices, factors associated with early supplementation and the effects of supplementation on duration of breast-feeding in a random sample of sixty northern Thai breast-fed infants studied prospectively from birth to 2 years of age. Composition of supplementary foods, energy and protein intake from supplements and changes in the supplementary diet with increasing infant age are also described. Rice-based foods were given from soon after birth; 81% of the sample had received supplements by 6 weeks of age. Early supplementary feeding was significantly associated with rural residence, large household size, maternal employment in agriculture and maternal age. Girls and infants with lower birth weights tended to be supplemented earlier. Despite early feeding of supplements, breast-feeding was prolonged, with median duration of 12 months. Early introduction of supplements and quantity of supplements consumed in the first 3 months were not associated with duration of breast-feeding. However, mothers who gave infant formula as the first supplementary food stopped breast-feeding slightly earlier, as did younger mothers living in households with more children.

Successful sustained lactation following postpartum tubal ligation.

This study was undertaken to see whether tubal ligation performed within days postpartum, and associated with a delay in the initiation of breastfeeding, exerts a disruptive influence on successfully establishing lactation among the rural population of northern Thailand. Lactational performance of 12 rural northern Thai mothers was not affected by the delay in reunion of mothers with their babies as a result of postpartum tubal sterilization procedure when compared with a group of 8 other healthy mothers and babies. The volume of breast milk transferred, frequency of breastfeeding and the total feeding time spent on the breast were similar on days 15, 45, 90, 180 and 360 postpartum. This finding suggests that the pattern of intense breastfeeding activity as practiced by this group of mothers has a stronger influence on prolonged and successful lactation than early contact in the immediate postpartum period.

The Chiang Mai lactation project: study design and implementation.

The Chiang Mai lactation project is a longitudinal field study of human lactation carried out among northern Thai women living in the Sanpatong area of Chiang Mai Province. Its aim was to measure the volume and composition of breast milk transferred from mothers to their infants in the first year postpartum, and to relate it to predictors of milk production, and to the growth of the child. Breast milk and supplementary food intake, and nursing patterns, were recorded over two consecutive 24-hour periods six times during the first year. Samples of breast milk and of supplementary foods were analysed for energy and protein. Supplementary foods were also analysed for bacterial contamination. The growth of the child was measured, and health assessed using a combination of health diaries and examination by a physician. Recruitment to the study was excellent. After recruitment, two subjects left the study area, but otherwise only two dropped out, so complete sets of data covering these variables are available for 58 of the 62 recruited subjects.

PIP: In the Sanpatong area of Chiang Mai Province in Thailand, 50% of infants began solid foods by 6 weeks old. Further almost 50% of mothers 1 year postpartum used progestogenic injectables. The Chiang Mai Lactation Project consisted of a 1984-1985 cross sectional pilot study with 65 12 month old infants, a 1985-1987 longitudinal study with 62 cases and 55 control infants, and a 1987-1988 follow up study at the end of the 2nd year. The project aimed to relate volume and composition of breast milk transferred from mothers to infants during the 1st year to predictors of milk production and to growth. Health workers measured breast milk intake over 24 hours by test weighing using a K Tron electronic balance during the day. They adjusted this procedure to measure night breast milk intake. The balance weighed foods before and after each feed to measure supplementary food intake. Laboratory staff analyzed breast and supplementary food samples for energy and protein. Health workers recorded to the nearest minute the time when each infant attached to the breast and when it detached to measure duration. Health workers weighed the infants either every 30 or 60 days depending on the study, kept health diaries, and a physical examination to assess growth and health. 90% of the intended sample took part in the cross sectional study. At the end of this study, however, researchers identified other infants during a 2nd survey so the original subject list only covered 75% of the intended sample. They used this double survey procedure to improve identification of births for the longitudinal study which resulted in superb recruitment (only 2 subjects dropped out and 2 left the area). The study resulted in complete sets of data on all subjects. The researchers found the 1 tailed t test at the 5% level to have enough power if the population correlation coefficient was .3-.4.

Relationships between nursing patterns, supplementary food intake and breast-milk intake in a rural Thai population.

Relationships between nursing patterns, supplementary food intake and breast-milk intake were examined in a group of 52 Thai babies under 1 year of age. All data were collected over two consecutive days, 24 h/day. Total sucking time (min/day) and supplementary food intake (kcal/day) were significant predictors of breast-milk intake after allowing for the age of the baby: R-squared is 0.32 for sucking time and 0.39 for supplementary food intake. The two variables were themselves correlated (r is -0.47). The number of breastfeeds per day and their mean duration was determined for each case, counting each episode of attachment to the breast as a separate feed. Number and mean duration of breastfeeds were then evaluated as predictor variables. The duration of feeds had no predictive power. Number of feeds was linearly related to milk intake and combined with age was as good a predictor of milk intake as total sucking time (with R-squared 0.34). These results suggest that a simple count of breastfeeds is as valuable as more complex measures of sucking duration in predicting to breast-milk intake.

Oral contraceptives: effect of long-term use on liver vitamin A storage assessed by the relative dose response test.

Vitamin A status measured by the relative dose response (RDR) test was determined among groups of Northern Thai women who had used estrogen-containing oral contraceptives (OCs) with or without multivitamin supplements through 13 cycles. Mean serum vitamin A values were elevated approximately 40% above those of control subjects (intrauterine contraceptive device (IUCD) users) during OC usage. Daily (one capsule) or periodic (two capsules 7 d/mo) multivitamin supplementation that included 1700 micrograms vitamin A per capsule did not significantly influence vitamin A serum values. The RDR test after 13 cycles was elevated in one individual who had taken OCs and the periodic multivitamin supplement. It reverted to normal after supplementation with vitamin A. A single high-dose vitamin A supplement (68,000 micrograms) did not change circulating levels of the vitamin. Among this population there is little evidence that use of estrogen-containing OCs for greater than 1 y resulted in a physiologically significant deterioration of vitamin A status.

PIP: Vitamin A status measured by the relative dose response (RDR) test was determined among groups of Northern Thai women who had used estrogen- containing oral contraceptives (OCs) with or without multivitamin supplements through 13 cycles. Mean serum vitamin A values were elevated approximately 40% above those of control subjects (IUD users) during OC usage. Daily (1 capsule) or periodic (2 capsules 7 days/month) multivitamin supplementation that included 1700 mcg vitamin A/capsule did not significantly influence vitamin A serum values. The RDR test after 13 cycles was elevated in 1 individual who had taken OCs and the periodic multivitamin supplement. It reverted to normal after supplementation with vitamin A. A single high-dose vitamin A supplement (68,000 mcg) did not change circulating levels of the vitamin. Among this population there is little evidence that use of estrogen-containing OCs for more than 1 year resulted in a physiologically significant deterioration of vitamin A status.

Predictors of breast milk intake in rural northern Thailand.

A random sample of 52 mothers and infants from a rural area of Northern Thailand were studied in their homes for 48 h. Infants were breast fed on demand. Daytime feeds were test weighed with electronic averaging balances and nighttime intake estimated using a new method, Indirect Test Weighing. All feeds, both day and night, were timed to the nearest minute. Other variables measured by direct observation were infant weight, and supplementary food and water intake. Mean 24-h breast milk intake was 579 g (range 78-1,011 g) with a median between day coefficient of variation of 8.8%. The proportion of 24-h breast milk intake consumed at night ranged from 8 to 91%, and increased with increasing infant age. Significant positive associations were found between breast milk intake, and sucking time and infant weight. There were significant negative associations between breast milk intake and age, and supplementary food and water intake.

Infant weight in relation to nutritional intake and morbidity in northern Thailand.

A cross-sectional study of 58 infants (age range 2-53 weeks) was carried out in a rural area of northern Thailand. Total dietary intake (energy and protein from breastmilk and supplementary food) was measured directly during continuous observation over 48 h of randomly selected study subjects in their homes. Associations between infant weight and total energy intake, total protein intake and morbidity were analysed by multiple regression analysis. Up to 6 months of age, heavier infants had larger energy intakes, when age and birthweight were taken into account. In the 7-12 months age group, heavier infants consumed more protein and had fewer respiratory infections. Weaned infants older than 6 months were significantly heavier and consumed more protein than infants of similar age who were still receiving breastmilk. The lower protein intakes of the latter infants were due to the low protein concentration of breastmilk compared with supplementary food.

Indirect test weighing: a new method for measuring overnight breast milk intakes in the field.

Indirect test weighing (ITW), a new method for measuring nighttime breast milk intake, is based on separate weighings of the mother and infant at the start and end of the nighttime sleep period. All other incidental weight changes overnight are measured, so that the corrected infant's overnight weight gain and the mother's overnight weight loss are then accounted for by breast milk transfer and evaporative water loss (EWL) alone. The combined EWL is partitioned between mother and infant on the basis of metabolic body size (body weight raised to the power of 0.73). The infant's EWL is added onto the corrected overnight weight gain to give nighttime milk intake. A field validation study on 24 northern Thai infants, conducted in the subject's homes, in which ITW was compared with nighttime direct test weighing (DTW) on the same night, gives 95% confidence intervals for the method of +/- 39 g for a range of milk intakes of 77-344 g. Confidence intervals for estimates using feeding patterns alone, or multiplying 12 h intakes by a constant, range from +/- 104 to 180 g, indicating that these methods are insufficiently accurate for individual estimates.

Circadian variation in fat concentration of breast-milk in a rural northern Thai population.

1. Twenty-five northern Thai mothers, breast-feeding their infants on demand, were studied in their homes for 24 h. All breast-feeds were test-weighed and pre- and post-feed expressed breast-milk samples (0.5 ml) taken at each feed. 2. The fat concentration of milk taken during a feed showed significant circadian variation, with maximum values between 16.00 and 20.00 hours and minimum values between 04.00 and 08.00 hours. Fat concentration at the start and at the end of a feed also varied significantly over 24 h. 3. Multiple regression analysis showed that the most important predictor of fat concentration at a feed was the length of time elapsed since the previous feed--the longer this interval, the lower the subsequent fat concentration. Other significant predictors were the fat concentration at the end of the previous feed, and the milk intake at the previous and at the current feed. 4. Fat concentration declined between feeds in proportion to the length of time between feeds, but the decline was less between sleep feeds than between waking feeds. This would appear to be a reflection of the lower post-feed fat concentration and higher pre-feed fat concentration of sleep feeds compared with waking feeds, when other variables relating to feeding pattern are taken into account. 5. The larger the milk intake at a feed, the greater was the increase in fat concentration from the start to the end of the feed. The change in fat concentration was less in feeds taking place during the sleep period than in daytime feeds.

Estimation of 24 h breast-milk fat concentration and fat intake in rural northern Thailand.

1. The present study assesses the accuracy with which mean 24 h breast-milk composition can be estimated if milk samples can only be collected during the daytime. 2. Twenty-five northern Thai mothers, feeding their infants on demand, were studied in their homes for 24 h. All feeds were test-weighed and 0.5 ml pre- and post-feed expressed milk samples taken at each feed. 3. If daytime sampling was restricted to two breast-feeds, it was found that the best estimate of 24 h fat concentration was given by two randomly chosen daytime feeds, predicting 24 h fat concentration with 95% confidence limits of +/- 7.0 g/l (equivalent to 21% of mean 24 h fat concentration). 4. Alternative sampling methods using the mean fat concentration of the feed after 08.00 hours and after 18.00 hours, or the first two feeds after 12.00 hours, predicted fat concentration with 95% confidence limits of +/- 9.7 g/l and +/- 8.9 g/l (28 and 26% of mean 24 h fat concentration) respectively. 5. If well-tolerated by mothers, it would be preferable to sample all daytime feeds, since this reduces the 95% confidence limits to +/- 3.3 g/l, equivalent to 10% of the mean 24 h fat concentration.

A study of adrenal corticol function and its reserve activity in long-acting injectable contraceptive users.

Adrenal function and its reserve capacity were studied in eighteen healthy non-lactating women who received depot-medroxyprogesterone acetate (DMPA: 9 subjects) and norethisterone enanthate (NET-EN: 9 subjects) as long-acting injectable contraceptives. Methodological assessments included: (i) morning fasting concentration of serum cortisol; (ii) diurnal variation of adrenal corticol activity as evidenced by cortisol concentration in serum samples taken at 0700 and 1600 hours; (iii) urinary free cortisol excretion; and (iv) cortisol response to insulin-induced hypoglycaemia. None of these assessments was significantly altered by contraceptive administration. This finding indicates that the subject's ability to release cortisol in response to a stressful situation, as well as to normal day-to-day activity, was not impaired by these contraceptive steroids.

PIP: Adrenal cortical function and its reserve capacity were studied in 9 women who received depot medroxyprogesterone acetate (DMPA) and in 9 women who received norethisterone enanthate (NET-EN) as long acting injectable contraceptives. Adrenal function was assessed by means of morning fasting concentration of serum cortisol, diurnal variation of adrenal corticol activity, and measurement of free urinary cortisol, and cortisol release in response to insulin-induced hypoglycemia. These assessments were made both prior to and at intervals after the initiation of contraceptive treatment. Data were combined and presented in 4 blocks: before treatment; 30 days after 1st injection; during treatment (data from 3rd, 4th, and 5th assessments); and after treatment (6th assessment made 6 months after the last injection). Neither the fasting concentration nor the circadian rhythm of cortisol were significantly altered by the use of either form of gestagens, not even when subjects were exposed to a relatively high level of these steroids during the first 30 days of their injection. It seems likely that the slight but insignificant decrease in the mean levels of cortisol following the introduction of gestagen injectable contraceptives is related primarily to reduction of the plasma binding protein. The mean level of free cortisolin 24-hour urine collections remained unchanged in both groups of subjects, confirming that adrenal function remained essentially unchanged in injectable contraceptive users.

Indirect test weighing: a non-intrusive technique for estimating night-time breast milk intake.

Indirect test weighing (ITW), for estimating night-time breast milk intake, is based on separate weighings of mother and infant before and after night-time sleep. Weight changes due to the exchange of milk overnight are reciprocal, so that if all other sources of weight change (eg, urine loss, supplementary fluid intake) are either controlled or measured, the difference between the mother's overnight weight loss and her infant's overnight weight gain represents their combined net evaporative water loss (EWL). The proportion of the combined EWL due to the infant is partitioned out as a function of the relative metabolic body sizes (kWt0.73) of mother and infant, and added to the infant's net overnight weight gain to provide an estimate of night-time breast milk intake. Validation studies, conducted in Northern Thailand, in which ITW was compared with direct test weighing (DTW) at each night feed, are reported for 13 infants over 3 nights at 5 d of age, and for 19 infants over 2 nights at 6 weeks of age or more. The regression equation for estimated milk intake against measured milk intake across all ages was y = 0.988x + 2.75, r = 0.927, n = 69 with 95 per cent prediction intervals of +/- 36 g for a range of intakes of 0-250 g. Rigorous control of data collection and taking account of the infant's age suggest that the prediction intervals for individual estimates can be improved to +/- 18 g at 5 d, and +/- 27 g at 6 weeks and over. Theoretical aspects of the relationship of EWL to body weight are discussed with a view to optimizing the accuracy of the technique.

The automatic sampling shield: a device for sampling suckled breast milk.

The automatic sampling shield uses the negative pressure exerted by the breast-feeding baby during sucking to withdraw a series of small samples from the milk stream. Shield performance was studied at four feeds for each of 13 babies. Acceptance of the shield was good (96% of feeds) and samples were obtained in 88% of feeds. Sample weight was large enough for micro-biochemical analysis of composition (median weight 1.3 g), without depriving the baby of important amounts of milk (median percentage of weight of milk intake was 4.3% and sample weight was less than 5 g in all cases). The shield should sample a constant proportion throughout the feed, in order to obtain a sample that is representative of the infant's nutrient intake. Fractional test-weighing of feeds showed a tendency for a larger proportion of the feed to be collected at slower flow rates. Modelling on the basis of the observed flow profiles in conjunction with a theoretical fat concentration profile showed that the observed 'disproportionality' would have over-estimated fat intake by a mean of 2.6% per feed (S.D.9.1 range -18.9% to + 16.9%). Using the shield in random sequence at two out of the first four feeds after 0800 h, showed that an infant's mean milk intake with the shield was on average 32% less than on control feeds. Allowing for possible compensation by the infant when control feeds followed low shield intakes, mean milk intakes with the shield were 17% smaller than without the shield.