Skip to main content

Currently Skimming:

5 Effects of Diet and Physical Activity in Pregnant Human Populations
Pages 143-174

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 143...
... Far more studies have focused on fetal growth and gestational duration than on the other outcomes; consequently, these will receive more attention here. Feml growth and gestational duration are the two determinants of birth weight, and from an international health perspective, birth weight is the most readily available index of pregnancy outcome.
From page 144...
... TABLE 5-la Methodologic Standards Used To Assess Published Studies Bearing on Maternal Energy Intake, Physical Amity, and Gestational Weight Gain Gestational Ph~ical Energy Weight Gain Activity Intake Definition of Target Population and Stud`'r Sample Description of Study Participation and Follaw-Up Rates Demonstration of Appropnate Tempom1 Sequence Between Factor and Outcome X Use of Detrimental Design X X X X X X X X TABLE 5-lb Confounding Variables Requiring Control Used To Assess Published Studies Bearing on Maternal Energy Intake, Physical Activity, and Gestational Weight Gam l Racial/Ethnic Origin X X Maternal Height X X Prepay Weight X X X MaternalAgea X X X S~nomic Status X X X Energy Intake X Physical Activity X Protein Intake X Cigarette Smoking X X X Alcohol Consumption X X X a Parity was accepted as a prosy control variable for maternal age. EllECrS OF ENERGY INCAS Background An important issue In studying energy intake is the difEalltr in measuring it.
From page 145...
... In addition to its role as a potential confounding variable, prepregnant nutritional status, as reflected ~ prepregnangy weight, weight-for-height, or skinfold thickness, is also likely to mod the erect of energy intake on fetal growth. In other words, it might be expected that thin women would derive a greater increase in birth weight for a given intake of energy than would well-nounshed or overnounshed women.
From page 146...
... fond a significant association, and those, though more recent and based on a larger sample, contradicted two previous reports of the same study of energy supplementation in Guatemala (Habicht et aL, 1974; Lechtig et al., 1975~. No effect on mean gestational age or rate of preterm delivery was reported in other energy supplementation trials (McDonald et al., 1981; Rush et al., 1980~.
From page 147...
... Quantitative estimates of the effect of energy supplementation on fetal duration and fetal growth are summ~ed in Table 5-~ TABLE 5-2 Effect of Energy Supplementation on Gestationa1 Age, Preterm Birth, Birth Weight, and Intrauterine Growth Retardation Outcome Erect Gestational Age None Preterm Birth None Birth Weight In women poorly nourished 99.7 g/100 kcaUday supplemented before pregnancy throughout pregnangya Lit women well-nounshed 34.6 g/100 kcaVday supplemented before pregnancy th~ughotat pr~n~ Intrauterme In women poorly nourished RRb: 0.47 GO before pregnancy Retardation In women well-nounshed PRb: 0.g2 before pliancy a Throughout pregnancy indicates that the supplement is given for 2~ days. Durations of supplementation shorter than 280 days would require proportion~teh,r more calories per day.
From page 148...
... South comments on the data presented by saying There is no reason to assume they are accurate or that conclusions can be drawn from them.n A hospital-based study from New York City tried to identify relationships between prepregnant nutritional status and all forms of spontaneous abortions, including those of a particular chromosomal type. It found no associations (Stein, 1989~.
From page 149...
... Thus low intake would be expected to reduce the Ask of high birth weight (> 4,000 g) and the corresponding increased Ask of dysfunctional labor, forceps delivery, both trauma, and Caesarean section (Hoff and Potter, 1979; Modanlou et al., 1980; Boyd et al., 1983)
From page 150...
... Other factors that may confound the effect of energy expenditure include age, panty, height, prepregnan~y weight, general health status, racial or ethic origin, socioeconomic status, and smoking and alcohol consumption. In considering the ejects of posture, fatigue, stress, physical fitness, hyperthermia, or other aspects of maternal physical activity on pregnancy, energy intake nabs not be controlled; however, other potential confounding famors would be similar to those mentioned above.
From page 151...
... found that Vermont women who continued endurance-type exercise, including jogging, moss counny swing, or aerobic dancing, during the third trimester of pregnancy had significantly shorter gestations than those who were either sedentary or stopped vigorous exercise of this kind before the third semester. These results should be interpreted with caution, however, since they are based on only 29 women who continued exercising, and several potentials confounding variables were incompletely controlled Barrett and Spellapy (1983)
From page 152...
... (1983) found no elevation in risk of delivery in working mothers aver potential confounding vanables were controlled, and there were no bivanate associations among preterm delivery and any of the following: physical position dig work, lifting or carrying, weights of loads, frequent of lifting, number of hours worked, hours of housework per week, the apse of an assistant for housework, climbing stairs, or hours of child care per work weed In fact, light and moderate leisuretime physical activity was associated with a significantly reduced Ask of preterm bum.
From page 153...
... In a recent study of nonphysician hospital workers earned out by the same group of French investigators, the duration of the work week and commuting time had no effect on the preterm birth rate (SaurelCubizolles et al., 1985~. Ancillary workers involved in strenuous cleaning, carrying heavy loads, and prolonged standing had higher preterm delivery rates; however, after controlling for differences ~ ethnic one, these differences were no longer statistically significant A more recent report by the same group of French researchers found that employed immigrant women, most of whom work in manual and seance jobs requinug that they carry heavy loads or remain in a standing position or both, had no increased risk of preterTn delivery (Stengel et al., 1986~.
From page 154...
... also was associated with higher birth weights and raises the question of whether errors In assessing gestational age may have led to the observed findings. A recent observational study from a U.S.
From page 155...
... has reviewed several studies from the late nineteenth and the twentieth centuries indicating that birth weights were higher in women who worked in a sitting position dig pregnancy than in those who worked standing and were higher in indigent working women who rested during the latter part of gestation than in those who continued world und1 the time of delivery. This combined evidence led Bnend to hypotheses that the posture-related eject on uterine blood flow is the physiological mechanism that inhibits fetal growth.
From page 156...
... Several reports from The Gambia document lower birth weight dunog the labor-~ntensive wet season, but this effect is likely to be confounded by lower food availability and higher Cadence of malarial disease during the wet season (Prentice et al., 1981; Whitehead et al., 1978~. The evidence from developed countries is mixed Two recent, wellcontrolled studies from Boston reported no effect of maternal work on fetal growth (MarbuIy et al., 1984; Zuckerman et al., 1986~.
From page 159...
... They should also distinguish, whenever possible, between the effects of energy expenditure, posture, fatigue, and stress and as for energy intake, should control for differences ~ wiechons morbidity that may be associated with both differences in physical activity and eject on fetal growth. Energy intake should be held constant when trying to isolate the effect of energy expenditure, and net energy balance should be held constant when eying to examine non-energy-related effects.
From page 160...
... None of these studies is definitive, and none provides sufficient evidence on which to base quantitative risk estimates. As with spontaneous abortion, no direct evidence pouts to exercise or other physical activity as the cause of the hyperthe~a among these women, and infection may well have been responsible for both the hyperthermia and the reported malformations.
From page 161...
... associated with increased duration and intensity of le~sure-time physical activity, even after controlling for prepregnanc~r physical activity and work dig pregnancy, diastolic blood pressure before 20 weeks, and a variety of other covanates. A similar, albeit nons~ficant, protective eject was seen with pregnanc,duced hypertension alone (i.e., without proteinuna)
From page 162...
... First, we can assess these effects indirectly by examining the evidence relating gestational weight gain (GWG) to pregnancy outcome bemuse GWG represents a net balance between maternal energy intake and energy expenditure.
From page 163...
... rather than the total number of kilograms gained over the pregnancy. In assessing the effect on fetal growth, overall GWG (or, preferably, net weight gain; be., after subtracting the infant's birth weight)
From page 165...
... The causal effect of maternal gestational weight gain on both weight may have been overestimated, however, since few of the examined studies subtracted the weight of the newborn from the maternal weight gem in assessing the association between GWG gain and birth weight Although most of the studies originated Mom pnvileged populations in developed countries, studies in Peru (Fnsancho et al., 1984) and in a sample of black women of low socioeconomic status in New York City (Rush et al., 1972)
From page 166...
... on Gestational Age, Preterm Birth, Birth Weight, and Intrauterine Growth Retardation for Women ninth Adequate Prepregnan~ Mutation Outcome Effect Ges,tat~onal Age Preterm Birth Birth Weight intrauterine Growth Retardation None None 20.3 g/kg total GWG Bra: 1.98 a RR: relative risk of intrauterine growth retardation in women with total ges,tational weight gain <7 kg versus, those with ges,tational weight gain > 7 lag. SOURCE: Kramer, 1987.
From page 167...
... DIRECT EVIDENCE OF COMBINED EFFECTS Previously cited studies from The Gambia have also provided some direct evidence concerning the combined effects of low energy intake and high energy expenditure (Prentice, 1980; Prentice et al., 1981~. As discussed earlier, these studies found a substantial decrement in birth weight during the wet season, when food availability is lowest and agricultural labor demands are highest.
From page 168...
... using data from the U.S. Collaborative Pennatal Project both found a greater reduction in birth weight attn~utable to maternal work in women with low prepregnant weight and gestaiional weight gain.
From page 169...
... 1984. Influence of growth status and placental function on birth weight of infants born to young still-growing teenagers.
From page 170...
... 1987. Determinants of low birth weight: A methodologic assessment and synthesis.
From page 171...
... 1989. Weight gain and pregnancy outcome in underweight and normal weight women.
From page 172...
... II. Effects of diet, cigarette smol;ing, stress, and weight gain on placentas, and on neonatal physical and behavioral charactenstics.
From page 173...
... 1980. Effects of maternal unde~nutntion and heavy physical work during pregnancy on birth weight.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.