Total Amount and Pattern of Weight Gain: Physiologic and Maternal Determinants

total weight change during pregnancy can vary from a weight unit personnel casualty to a reach of more than 30 kilogram ( 66 pound ). This wide variation in profit among healthy fraught women appears to be attributable to several physiologic and environmental factors. For exercise, changes in the secretion of parental hormones and early physiologic adjustments associated with pregnancy undoubtedly affect the utilization of energy sources and therefore the total of weight gained. Certain parental characteristics and health habits may besides exert an influence. In this chapter, the subcommittee reviews these physiologic factors and evaluates the relationship between selected maternal characteristics and the amount and practice of reach. A discussion of relationships between dietaryand auxiliary energy intake and weight derive is found in chapter 7. Weight gain attributable to body water is the most variable of the components. A report positive kinship between the increased full torso water and baby give birth weight ( Hytten, 1980b ) suggests that water accretion is beneficial. An estimate of the pattern of weight composition for each quarter of pregnancy is depicted in. version in the composition of gain is discussed in chapter 6. Hytten ( 1980b ) estimated that, on average, water contributes approximately 62 % of the sum acquire at term, fat contributes 30 %, and protein contributes 8 % ; but there is considerable variation in these values. Of the sum fatten reach, 90 % is deposited as enate stores. About 60 % of the full protein accretion is located in the products of conception ; the remainder is accounted for by the profit of enate uterine, mammary, and blood tissues. In early nitrogen counterweight studies, reported protein retentions were higher than could be accounted for by those fetal and maternal tissues. however, holocene studies conducted in metabolic wards have reported protein retentions comparable to the estimated want for pregnancy. Women normally accumulate fat during pregnancy. Hytten ( 1980b ) estimated that pregnant women who gain 12.5 kilogram ( 27.5 pound ) without edema acquire about 3.5 kg ( 7.5 pound ) of fat. ( See Chapter 6 for other, more late estimates. ) The aim of the fat shop is uncertain : it may be a maternal energy reserve for use when the food add is limited during either pregnancy or lactation.

In women without generalize edema or with lone stage edema, an expansion of the extracellular, extravascular fluid volume accounts for approximately 13 % of the total profit. The memory of extracellular fluid can be highly variable ; some women accumulate more than 5 liters ( 5 kilogram, or 11 pound ). The physiologic footing for extracellular fluent retention is changeable. placental estrogens may increase the affinity for water of mucoor glycopolysaccharides in conjunction weave ( Hytten, 1980b ), resulting in an expanded, softer tissue. expansion of the blood volume accounts for 10 % of the entire addition. The increase in plasma volume ( approximately 50 % ) is greater than that of the red blood cellular telephone multitude increase, but expansion of both is related to fetal size ( Hytten, 1980b ). Most of the increase in plasma volume occurs before week 34 of gestation ; the increase in red blood cell aggregate is believed to be linear from the end of the first spare to term. Iron supplementation increases the expansion of the red lineage cellular telephone batch ( see Chapter 14 ). expansion of maternal tissues accounts for approximately two-thirds of the sum gain. In addition to increases in uterine and mammary tissue mass, there is an expansion of maternal blood book, extracellular fluid, fatten stores, and possibly early tissues. In lab animals, an increase in liver and intestinal mucosal mass during pregnancy is apparent, but there is no evidence that these tissues increase in fraught women. The components of acquire can be divided into two parts—the products of conception and maternal tissue accretion. The products of creation constitute the fetus, placenta, and amniotic fluid. On the average, the fetus represents approximately 25 % of the entire derive, the placenta about 5 %, and the amniotic fluent about 6 % ( Hytten, 1980b ). cross-sectional data indicate that fetal growth follows a sigmoid wind, with emergence slowing in the concluding week of gestation. The rate of placental emergence declines toward the end of pregnancy. To determine a physiologic norm for rate of addition during the final half of pregnancy, Hytten and Leitch ( 1971 ) extracted weight gain data from records maintained by the Aberdeen Maternity Hospital for 486 healthy women aged 20 to 29 and at least 160 centimeter ( 63 in. ) tall, who delivered their infants between weeks 39 and 41 of pregnancy ( between 1950 and 1955 ). No try was made to control weight profit by food limitation in this population. The most park value for the rate of gain during the last half of pregnancy was between 0.41 and 0.45 kilogram ( ~1 pound ) per workweek, but the range of advance was identical wide—from less than 0.1 to 0.9 kg ( 0.2 to 2 pound ) per workweek. The datum from this study are shown in, which has been used widely to evaluate the rate and total come of system of weights gained by meaning woman. Hytten and Leitch emphasized, however, that considerable variation of this radiation pattern is reproducible with good pregnancy outcomes. The lowest incidence of preeclampsia, abject parentage weight, and perinatal death was associated with gaining 0.45 kg/week during the stopping point 20 weeks of pregnancy. The following rates were established for each quarter of pregnancy among primigravid women : In 1971, Hytten and Leitch established physiologic norms for total slant gain, the rate of acquire in the concluding half of pregnancy, and the rate of profit associated with the best generative performance. Using data from two british studies ( Humphreys, 1954 ; Thompson and Billewicz, 1957 ) of more than 3,800 women, they concluded that the physiologic average total profit of “ healthy primigravid women eating without restriction ” is 12.5 kilogram ( 27.5 pound ) —approximately 1 kg ( 2.2 pound ) in the inaugural clean-cut and the remainder during the last two trimesters. For multigravid women, they made no specific estimates but suggested that a slightly lower acquire could be expected. standard errors for the rates of weekly gain were given in alone one published report that included a big sample size ( Thomson and Billewicz, 1957 ). From these data, the subcommittee estimated the system of weights advance at the 15th and 85th percentiles of advance for scottish primigravid women at different stages of pregnancy, as follows : There are no datum on rates of burden gain by shipshape that are representative of the U.S. population. however, given the remarkable similarity in the rates that can be interpreted from, it is likely that a congressman sample of the U.S. population would have rates like to those represented by most other population groups. Studies suggest an average gain of approximately 0.45 kg ( 1 pound ) per week during the second clean-cut and a slightly lower gain of about 0.40 kg ( 0.9 pound ) per workweek during the third tailored. Thomson and Billewicz ( 1957 ) reported that 40 % of their population gained their suggest amount of 3.6 to 5.4 kg ( 8 to 12 pound ) during the second trimester, whereas about 25 % gained less. The investigators did not relate the pattern of amplification to pregnancy result. however, only 14 % of their sample gained amounts within the ranges the investigators considered to be ideal for both the second and third trimesters. thus, the individual experience of many meaning women is improbable to fit the convention depicted in. few investigators have evaluated slant acquire during the foremost shipshape in detail. Clapp et aluminum. ( 1988 ) weighed 20 physically active, well-fed women serially from before concept to week 15 of pregnancy and showed that parental reach averaged 2 kilogram ( 4.5 pound ) at 7 weeks and 4.3 kilogram ( 9.5 pound ) at 15 weeks ; the average rate of gain from 0 to 15 weeks of gestation was 0.29 kilogram, or 0.6 pound, per week. Weights beyond this period were not given. only four reports of the rate of derive have appeared since 1971. In a 1977 study of weekly weights of 2,000 meaning japanese women, the mean rate of profit was 0.45 kilogram ( 1.0 pound ) per workweek between 16 and 24 weeks and 0.48 kg/week between 24 and 32 weeks of gestation ( Kawakami et al., 1977 ). Meserole and colleagues ( 1984 ) constructed a graph of the weight addition pattern of 80 meaning girls aged 19 or less. The gradient of the rate of gain for the adolescents was described as steeper than that for pornographic fraught women. In a survey of 1,000 pregnant women in Indonesia ( Husaini et al., 1986 ), the rate of gain and total advance were lower than those reported in the other studies. The mean prepregnancy weight for the indonesian women was 44.5 kilogram ( 98 pound ), well less than that of women in the United States. Brown and coworkers ( 1986 ) studied the form of gain of 459 low-income women who delivered infants weighing between 3,000 and 4,500 g. The weekly rates of enate weight gain by this group were higher during the beginning two trimesters than has been reported in early studies ( ), namely, 0.22 kilogram ( 0.5 pound ) per week during the inaugural clean-cut and 0.52 kilogram ( 1.1 pound ) per week during the second spare, but they were comparable ( 0.40 kilogram, or 0.9 pound, per week ) during the third base clean-cut. A deceleration of weight profit or a flimsy weight loss has been systematically reported as women approached term ( Cummings, 1934 ; Kuo, 1941 ; Robinson et al., 1943 ; Scott and Benjamin, 1948 ). Although the report designs and populations differed among these studies, the slopes of the lines representing accumulative weight gains were quite like. As mentioned above, Hytten and Leitch ( 1971 ) suggested a addition of 0.41 to 0.45 kg ( ~1 pound ) per week as a citation for the survive half of pregnancy. similarly, Thomson and Billewicz ( 1957 ) concluded from their cogitation of 2,868 normotensive Scottish primigravid women that an average profit of about 0.45 kg ( 1 pound ) per workweek during the second base half of pregnancy was a ”sound and realistic average to aim at ” ( p. 247 ). Rates of derive observed by Thomson and Billewicz ( 1957 ) were 0.467 kg/week ( criterion deviation [ SD ] = 0.161 ) between 20 and 30 weeks of gestation and 0.395 kg/week ( SD = 0.213 ) during weeks 30 to 36. Reported rates of gain of U.S. women during the lapp time time period were lower than those observed in the United Kingdom ( Robinson et al., 1943 ; Tompkins and Wiehl, 1951 ). Robinson and coworkers stressed that convention and fleshy patients were told to limit their inhalation of carbohydrates and fat. The highest rate of gain occurred during the one-seventh lunar calendar month of gestation ( Robinson et al., 1943 ) ; between 20 and 28 weeks of gestation, the rate of gain averaged approximately 0.455 kg ( 1 pound ) per week. not lone did total weight gain disagree among studies, as mentioned above, but there were besides differences in the amount of weight gained at specific points during gestation ( ). In the study by Brown et aluminum. ( 1986 ), mean weight gains were higher at each gestational menstruation. Patterns of amplification are illustrated in, which shows the accumulative gain reported in the 12 studies, and in, which provides data from selected studies of well-fed women with uncomplicated pregnancies in the United States and the United Kingdom. In the studies summarized in, women were weighed when they entered prenatal care ( at 13 or 16 weeks of gestation ), then normally once per month until about workweek 30 of gestation, and more frequently after that. Weight change at particular weeks of gestation was observed or interpolated from these data. In most studies, weight change was based on mensural system of weights at the first base visit ; in others, it was based on recall prepregnancy weight. few studies collected data on weight amplification during the first shipshape. Most of them excluded women with obvious pregnancy complications, but some studies provided few descriptive data about their samples. baffling characteristics of some studies include prescribed weight limitation, limitations of samples to hapless women, and a dispatch lack of information about sample excerpt. Infant birth weight, an important standard for healthy pregnancy consequence, was rarely considered. Data from 12 other studies on gestational weight addition are shown in. These studies were selected because they provided data on accumulative addition in maternal weight at versatile times during pregnancy, frankincense permitting weight profit patterns to be estimated. These data were obtained from six countries and cover a cross from 1925 to 1982. Three of the studies ( Brown et al., 1986 ; Husaini et al., 1986 ; Kawakami et al., 1977 ) were reported after release of the Food and Nutrition Board ‘s report, Maternal Nutrition and the Course of Pregnancy ( NRC, 1970 ). The study by Brown et alabama. ( 1986 ) provides the most holocene data regarding women living in the United States. Reported average sum gains ranged from 10.1 to 14.9 kg ( 22 to 33 pound ) across samples in these studies. From the published datum, it is extremely difficult to identify a physiologic average for sum system of weights gain during pregnancy. The most spokesperson data for sum weight profit in the U.S. population are from the 1980 National Natality Survey ( NNS ) ( Taffel, 1986 ), which is a probability sample of all live births to U.S. women in 1980. Because of the express sum of information available from published reports, the subcommittee relied heavily on the datum from the 1980 NNS to determine the independent effects of maternal characteristics on total system of weights derive ( Kleinman, 1990 ; Taffel, 1986 ). The distribution of gains among white, non-Hispanic, married mothers by body mass index ( BMI ) ( Kleinman, 1990 ) is shown in and. In compendious, the net effects of the hormonal changes during pregnancy are increased tendencies to store overindulgence energy as maternal fat after meals and to mobilize these energy-dense stores in the fast state. Amino acid uptake is increased after meals, but amino acid spill is reduced during fast, causing a net conservation of enate lean weave. Adjustments in adipose tissue utilization occur between meals to provide for maternal department of energy needs while conserving glucose and amino acids for fetal fuel and synthesis of enate and fetal tend weave. The hormonal adjustments of pregnancy may alter use of energy sources, resulting in a reduce energy monetary value for the synthesis of fatten or protein. The energy price of weave deduction has not been measured in meaning women. The fetus requires an uninterrupted source of glucose and amino acids for increase. The placenta produces hormones, for example, human placental lactogen, whose major metabolic effects are to promote greater practice of lipids as an energy source by the beget. This may increase the handiness of glucose and amino acids for fetal use. Following a meal, maternal glucose uptake is reduced, despite increased plasma concentrations of insulin ( Kitzmiller, 1980 ). Human chorionic somatomammotropin, progesterone, and hydrocortisone levels increase during pregnancy and contribute to a rise in parental peripheral insulin resistance. This insulin resistance seems to be specific for maternal glucose consumption ; amino acid consumption and the pace of liverwort conversion of glucose to triglycerides are not impaired. Following a meal, plasma amino acid concentrations are lower in pregnant women than they are in nonpregnant women, probably because of placental uptake and insulin-mediated increases in protein synthesis. The liverwort conversion of glucose to triglycerides besides is increased in pregnant women after a meal. This increased inclination to synthesize triglycerides promotes energy storage. With fast, these fat reserves are mobilized. At the same time, mobilization of parental brawn multitude remains moo because of the higher insulin-to-glucagon ratio, and maternal tilt tissue is conserved. It is unsealed whether a change in food consumption is all-important for a gain of maternal and fetal weave. A convinced energy balance and, consequently, a issue of energy for weight gain may be achieved by an increase in department of energy intake, a decrease in department of energy outgo, an addition in the efficiency with which energy is used to synthesize new weave, or some combination of these factors. ( For a more detail discussion of energy proportion during pregnancy, see chapter 7. ) It is unmanageable to measure food consumption precisely, but longitudinal studies of well-fed fraught women on unrestricted diets show a modest, but not constantly significant or universal, increase in energy intake. To estimate the energy monetary value for weight gain during pregnancy, the theoretical energy necessitate ( approximately 85,000 kcal ) ( Hytten, 1980a ) was divided by the common weight derive ( 12,500 gigabyte ), yielding an department of energy cost of 6.4 kcal for every gram of slant derive. however, the measured energy prerequisite for pregnancy and weight profit in the late Five Nation Study totaled 55,000 kcal for a 11,800-g gain ( Durnin, 1987 ), or 4.7 kcal/g of weight gain. Both estimates of the energy cost of gain during pregnancy are lower than the 8.0 kcal/g required for weight profit by nonpregnant women ( Forbes, 1988 ). The lower energy need for weight unit profit in pregnancy probably reflects the higher body of water content of the lean weave that is gained .

Maternal Determinants of the Pattern and Amount of Weight Gain

As mentioned earlier, gestational weight reach differs widely among healthy women delivering single, full-term infants, partially because of differences in parental characteristics such as prepregnancy weight-for-height status, long time, parity, ethnic origin, socioeconomics status, substance misuse, and physical natural process level. The influence of these characteristics on gestational system of weights addition is discussed below .

Prepregnancy Weight-for-Height Status

The weight-for-height status of the beget before creation is frequently used as a marker for the mother ‘s nutritional express before a pregnancy. A depleted weight-for-height is assumed to reflect fringy tissue reserves, whereas a high prize is believed to be indicative of excessive reserves. Methods of expressing weight-for-height status are discussed in chapter 4. Kleinman ( 1990 ) presented the distribution of total slant gains according to four BMI groups : < 19.8, 19.8 to 26.0, 26.1 to 29.0 and > 29.0, i.e., low, moderate, senior high school, and identical high system of weights for height. The subcommittee located 10 reports published between 1970 and 1989 on the kinship between maternal prepregnancy weight-for-height condition and weight profit ( see ). The sample distribution sizes ranged from 20 to approximately 1,500 women. Most studies included lone women who were registered for prenatal worry in the first spare. Prepregnancy weight-for-height status normally was based on hark back prepregnancy weight and on height measured at the beginning prenatal visit. In a few cases, weight at the first visit was used. In some studies, the patients were classified by the 1959 Metropolitan Life Insurance Company ‘s ( MLI ) standards ( Metropolitan Life Insurance Company, ( 1959 ). Otherwise, the subcommittee calculated BMI from the reported data, and the women were assigned to one of the five groups identified in. All the studies excluded women with multiple births, preterm deliveries ( < 37 weeks of gestation ), and women with obvious pregnancy complications. In several studies with fewer than 100 women per group, data collection was prospective. In the larger studies, the data were abstracted from clinic charts. Women from both populace health clinics and private practices are included in the data presented in.

TABLE 5-3

Gestational Weight Gain Reported by Maternal Prepregnancy Weight-for-Height Status in Different Studies of U.S. Women. shows that the sum gained by women in the five groups differed among the studies. For exercise, women in the low and normal weight-for-height groups studied by Mitchell and Lerner ( 1989 ) gained the least ( 9.3 and 8.4 kilogram, or 20.5 and 17.5 pound ), whereas those studied by Haiek and Lederman ( 1989 ) gained the most ( 15.5 and 15.8 kilogram, or 34 and 35 pound ). This discrepancy suggests that other differences in these two samples of women influenced total weight gain more than did their prepregnancy weight-for-height status. Divergent socioeconomic status may account for some of the differences : Haiek and Lederman ( 1989 ) studied women from public health clinics, including a high symmetry of teenagers, whereas Mitchell and Lerner ( 1989 ) studied women from a private practice. Given the disparate characteristics of the study samples, comparison of the influence of prepregnancy weight-for-height condition can be made entirely within single studies. only three of the studies ( Abrams and Laros, 1986 ; Brown et al., 1981 ; Mitchell and Lerner, 1989 ) provide data from women in more than two of these five weight-for-height groups. Mitchell and Lerner ( 1989 ) found that the gain of women in the broken and very low weight-for-height groups was significantly greater than that of normal-weight women ( 9.3 compared with 8.5 kg, or 20.5 versus 19 pound ). Brown and coworkers ( 1981 ) did not find any differences in gain between scraggy and normal-weight women. Abrams and Laros ( 1986 ) compared the burden addition of women in low, normal, high, and very high weight-for-height groups. No statistically significant differences in mean weight profit were found among women in the four groups, but the sum gain of women in the identical corpulence group tended to be slenderly lower than that of women in the normal and high groups ( 14.1 compared with 15.2 kg, or 31 versus 33 pound ). These investigators noted that the gains of the women in the very corpulence class were more variable than those of women in the early groups. Their coefficient of variation for acquire was 55 % compared with approximately 31 to 35 % in the other three groups. Among the very fleshy women in that study, there was a higher share of women with broken weight gains, which lowered the group median. The very corpulence women in this clinic were not told to limit their food inhalation or to restrict their system of weights gain. In these 10 studies, weight amplification by women in each of the five groups varied substantially ( ), and coefficients of pas seul of reach for women with normal prepregnancy weights ranged from 31 to 63 %. This degree of variation in amplification after controlling for differences in maternal body size shows that maternal prepregnancy weight-for-height condition accounts for only a humble part of the version in burden acquire. An analysis of the 1980 NNS data ( Kleinman, 1990, and ) showed that as parental prepregnancy BMI increased from chasten to very high, base full weight gain fell by about 5 kg ( 11 pound ), and the variation in addition increased. More than 10 % of the women in the very corpulence group lost weight during gestation, and more than one-third of the women in that group met the standard for depleted weight advance, i.e., a reach of less than 6.8 kilogram ( 15 pound ). The proportion of women with a low entire weight gain was about four times greater among women in the very high BMI group than among women in the low and moderate BMI groups. As shown in, only 25 % of those with a low BMI, 20 % of those with moderate and senior high school BMIs, and 13 % of those with very high BMIs had weight gains finale to the gain suggested by Hytten and Leitch ( 1971 ), i.e., between 11.8 and 13.6 kilogram, or 26 and 30 pound. The 1980 NNS report is compatible with the observations of Abrams and Laros ( 1986 ) that the gains of very fleshy women are lower on average and are more variable than those of early women, but it provided no attest that scraggy women were at an increased gamble of depleted weight amplification. This is an interest find, and follow-up studies are needed. There are entirely a few studies of the consequence of prepregnancy consistency weight on the pattern of slant profit. In one late report, Meserole and coworkers ( 1984 ) compared the blueprint of gain of scraggy, convention, or fleshy adolescents ( full sample size, 80 ). The only dispute observed was a gain by the normal-weight adolescents in the first clean-cut in comparison with short or no derive by adolescents in the other two groups, but the methods used to ensure the accuracy of the estimates of prepregnancy system of weights, and thus of early slant advance, were not described. The rate of advance by the normal-weight adolescents was slenderly lower in the second and third trimesters than that of the scraggy and fleshy adolescents ; sum weight unit gains did not differ. There was no far interpretation of these data, and the differences in weight derive radiation pattern were not tested for meaning. Results from studies conducted in the 1940s and 1950s of the effect of prepregnancy system of weights for stature on the rate of gain were inconsistent ( Robinson et al., 1943 ; Scott and Benjamin, 1948 ; Stander and Pastore, 1940 ; Thomson and Billewicz, 1957 ) .

Maternal Height

In a comprehensive revue of the literature, the subcommittee located alone one survey ( Kleinman, 1990 ) designed to determine whether there is an freelancer effect of parental stature on full weight amplification. In this cogitation, data from the 1980 NNS were analyzed by using multiple analogue regression techniques to control for BMI, historic period and parity, education tied, alcohol use, ethnic origin, and cigarette smoking ; a meaning impression of height on weight unit profit was observed. short-change women ( < 157 centimeter, or < 62 in. ) gained about 1 kg ( 2 pound ) less, on average, than did taller women ( > 170 curium, or > 67 in. ), but there was no evidence that brusque women had an increased risk of low weight reach. An earlier study focused on the relationship between stature and the form of gain ( Thomson and Billewicz, 1957 ), but no impression was identified. The independent effect of stature on the come and pace of gain needs far probe .

Ethnic Origin

Differences in the entire total of weight gained by black and white women during gestation were foremost reported by Eastman and Jackson ( 1968 ) in a study of clinic patients in Baltimore, Maryland, between 1954 and 1961. The full weight acquire of the egg white women averaged 9.9 kilogram ( 21.8 pound ), whereas that of the black women averaged 9.0 kilogram ( 19.8 pound ). The statistical significance of this deviation was not determined. The report beggarly weight gains of the women of both races was the lapp if the prepregnancy system of weights was greater than 82 kilogram ( 180 pound ). In two other big studies of weight reach conducted in the 1950s and 1960s, no dispute in weight advance between black and ashen women was detected ( Niswander and Jackson, 1974 ; Simpson et al., 1975 ). Both black women and white women in the collaborative Perinatal Project gained an average of 9.9 kg ( 21.8 pound ) ( Niswander and Jackson, 1974 ). similar gains were reported for black angstrom well as flannel wives of military men studied in San Antonio, Texas, between 1946 and 1966 ( Simpson et al., 1975 ). Multivariate analysis was not used in either of these studies to determine whether there was a statistically significant, independent impression of race on gestational weight advance. More holocene studies have focused on the effect of cultural beginning on weight addition in populations including white, black, Southeast Asian, and hispanic women. In an obstetric clinic for teenagers in San Diego, California, there was no significant remainder in the beggarly slant advance of white, black, and hispanic mothers ( Felice et al., ( 1986 ) ; but hispanic mothers tended to gain the most system of weights. In another study, Puerto Rican teenagers in New Jersey gained significantly less than white or black teenagers did ( Scholl et al., 1988 ). In Minnesota, Swenson et alabama. ( 1986 ) studied the burden gains of white, black, Hmong ( a Laotian tribe ), and other Southeast Asian meaning adolescents and adults. The entire derive of the Hmong and the other Southeast asian adolescents and adults was about 5 kg ( 11 pound ) less than that of their white and black counterparts. Different attitudes about food practices during pregnancy among Southeast asian women may contribute to their lower system of weights gains. The modal weight advance of white women in the 1980 NNS was significantly greater than that of black women ( 13.2 versus 12.2 kilogram, or 29.1 versus 26.8 pound ) ( Taffel, 1986 ). After controlling for the effects of prepregnancy weight, marital condition, education, and age combined with parity, ashen women hush gained about 0.5 kg more than black women did. The gestational period of egg white women tended to be approximately 0.5 week longer than that of black women, but this deviation only partially explained the higher gains of the ashen women. The mean weight gain of married hispanic women and white women did not differ, but the risk of low weight profit was twice equally high in Hispanics as it was in whites. Black women besides were at a 70 % greater risk for first gear levels of weight profit compared with whites. In compendious, a consistent effect of heathen origin on gestational weight gain is not apparent in the literature. Black women in the 1980 NNS gained importantly less than white women did. Differences in the gestational period did not account for all this dispute. The effect of parental heathen origin on the rate of weight gain has not been studied .

Age and Parity

There are many reports of weight gain and pregnancy consequence in adolescent women, but most do not control for parity, prepregnancy weight for height, gestational length, heathen origin, or alcohol and tobacco consumption when evaluating the effect of age on weight unit acquire. The results of nine studies of burden gain among adolescents published since 1970 are summarized in. adolescent mothers in Lima, Peru, gained from 1 to 7 kg ( 2 to 15 pound ) less than U.S. adolescents on the modal ( Frisancho et al., 1983 ), but the study is of value because of the big number of fraught teenagers of each class of age between 12 and 17. The mean weight gains of the peruvian teenagers between ages 14 and 17 did not differ. only 28 girls were between the ages of 12 and 13, but these girls gained about 0.8 kg ( 1.8 pound ) less than the older girls did. This dispute was not tested for statistical meaning. No consistent relationship between parental long time and weight gain was observed in the six studies of U.S. women. Three groups reported that young mothers gained more weight ( Ancri et al., 1977 ; Endres et al., 1985 ; Muscati et al., 1988 ), two reported that young mothers gained less burden ( Haiek and Lederman 1989 ; Meserole et al., 1984 ), and two found no dispute ( Horon et al., 1983 ; Loris et al., ( 1985 ). One group reported a kinship between gynecological long time and slant gain ; young girls had lower gains than the more mature girls did ( Meserole et al., 1984 ). This find, plus the notice that 12- to 13-year-old peruvian mothers gained less weight ( Frisancho et al., 1983 ), suggests that the slant gains of very young adolescents ( < 2 years after menarche ) may be lower than those of older adolescents. Further research is needed to confirm this ending .

TABLE 5-4

effect of Chronological Maternal Age on Gestational Weight Gain. multiple linear arrested development analysis was used to evaluate the effect of long time and parity on weight profit among women who participated in the 1980 NNS ( Kleinman, 1990 ). primiparous women in all historic period groups gained about 1 kg ( 2 pound ) more than multiparous women of the lapp old age did, and the risk of first gear weight gains was about one-third lower among primiparous women. After controlling for parity bit, differences in weight gain by long time were small. primiparous women of all ages gained more ( about 1 kg, or 2 pound ) than multiparous women of the lapp age. In compendious, the limited data hint that identical young mothers have lower gains than other women do. The effect of pregnancy after the historic period 35 or 40 on gestational weight acquire has not been studied. Thomson and Billewicz ( 1957 ) studied the relationship between enate age and the form of weight unit gain, and no relationship was found .

Cigarette Smoking

Results of multivariate analysis showed that the think of system of weights profit of marry smokers and nonsmokers in the 1980 NNS were exchangeable, but mothers who smoked cigarettes were 50 % likelier to gain less than 6.8 kilogram ( 15 pound ) than were nonsmoking mothers. Rush ( 1974 ) and Davies et aluminum. ( 1976 ) reported that female nonsmokers gain less burden than female smokers do, but early investigators have not found this effect ( Carruth, 1981 ; Meyer, 1978 ; Picone et al., 1982 ). It appears that smoke has a minor effect, if any, on mean gestational weight gain but a larger effect on hazard of low weight gain .

Alcohol and Illegal Substances

There are many reports on the effect of parental alcohol consumption on fetal growth and development, but few on the relationship between alcohol consumption and gestational weight gain. In a study of 204 alcohol abusers and 11,123 alcohol nonabusers ( Sokol et al., 1980 ), no differences were found in parental prepregnancy weight, stature, or gestational weight gain between the two groups. In another study of 270 pregnant women ( Tennes and Blackard, 1980 ), there was no correlation between alcohol use and gestational weight profit. In the 1980 NNS ( Kleinman,1990 ), alcohol consumption was found to have little effect on mean burden gain. Mean weight advance of control users of alcohol ( defined as those who drank more than once per month or more than two drinks per drink occasion ) was 0.2 kilogram ( 0.4 pound ) higher than that of women who consumed no alcohol. The risk of low weight profit was greatest among the nondrinkers. In a thorough review of the literature, the subcommittee found only one study ( Zuckerman et al., 1989 ) on the relationship between the manipulation of cocaine and marijuana and gestational weight unit gain. In that study, Zuckerman et aluminum. ( 1989 ) compared 202 marijuana users with 895 nonusers and 114 cocaine users with 1,010 nonusers among women attending the prenatal clinic at Boston City Hospital. The bastardly weight gain of marijuana users was 12.7 kilogram ( 28 pound ) compared with 14.1 kg ( 31 pound ) for nonusers. The use of these substances and early illegitimate drugs broadly is associated with a life style that is not supportive of good feed and health habits. therefore, it is not surprise that these women had lower intend system of weights gains during pregnancy .

Socioeconomic Status

information about family income was requested on questionnaires that were sent to marry mothers in the 1980 NNS ( Taffel, 1986 ). In a bivariate analysis, women from households with incomes above $ 30,000 per class gained 0.6 kilogram ( 1.4 pound ) more than did women from households with incomes of less than $ 9,000 per year. The hazard of low weight unit addition increased closely twofold as annual family income fell from $ 30,000 to $ 9,000. however, these results were not statistically controlled for other variables that could influence weight addition. marital status is besides linked with socioeconomic condition since female-headed households tend to have lower family incomes. On the average, marry mothers gained about 1 kg more than unmarried mothers did ( Taffel, 1986 ).

Data on the educational attainment of both married and unmarried mothers were analyzed in the multiple linear regression described by Kleinman ( 1990 ). mean weight reach was like for women in all educational groups, but compared with mothers with 13 or more years of education, the risk of gloomy slant gain was 50 % higher among mothers with < 12 years of education and 25 % higher among those with 12 years of education .

Work or Physical Activity

Studies on the effect of heavy function or forcible activity on weight gain should be interpreted with circumspection, because high energy consumption can be offset by increases in energy inhalation so that energy remainder is maintained. besides, it is unmanageable to determine whether the stress ( both physical and psychologic ) of work, alternatively of the increased energy expending, may have led to reduced weight gain. Some investigators have reported an lift risk of preterm manner of speaking among working women ( Mamelle and Munoz, 1987 ; Mamelle et al., 1984 ), whereas others have failed to identify such a kinship ( Berkowitz et al., 1983 ; Kaminski and Papiernik, 1974 ; Zuckerman et al., 1986 ). If work or physical activity reduced the length of gestation, sum weight profit would besides be reduced. measurement of the rate of gain could be used to adjust for differences in the duration of gestation. Although many studies have been conducted on the effects of work on pregnancy ( i.e., give birth weight, gestational duration, and complications of labor and manner of speaking ), those few that provide data on weight advance ( Naeye and Peters, 1982 ; Tafari et al., 1980 ) provide small utilitarian information about the effect of solve on burden amplification .

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