Maternal Physical Activity Research Articles

Maternal Physical Activity And Birth Weight

The CDC/ACSM (1995) recommendations for moderate physical activity (PA) (3–5 METs, ≥30 min, ≥5 d·wk−1) in healthy adults are currently advocated for pregnant women by the American College of Obstetricians and Gynecologists (ACOG, 2002). However, further research on birth outcome may be needed before ACOG endorses theCDC/ACSM recommendations for vigorous PA (≥ 6 METs, ≥20 min, ≥3 d·wk−1) during pregnancy. PURPOSE Using meta-analysis, we examined whether the relationship between maternal PA and birth weight was moderated by PA intensity. Additionally we examined the impact of maternal weight gain on birth weight. METHODS The literature search was performed using NLM Medline, Embase, and manual searching of bibliographies. Studies were screened to ensure they included a measure of physical activity during pregnancy (with a sedentary control group) and reported birth weight as a continuous variable within the normal birth weight range. A random effects model was used to calculate the pooled effect size (ES) of birth weight by maternal PA. Pre-specified subgroups (e.g., maternal age, maternal weight gain, study design) were used to examine potential heterogeneity. Meta-regression was utilized to estimate the amount of variance in birth weight between physically active and sedentary pregnant women that can be accounted for by differences in maternal weight gain. RESULTS Of 2418 potentially relevant studies located, 23 satisfied inclusion criteria after full-text review. Study participants were mostly Caucasian, nonsmokers, and nulliparous. Significant heterogeneity was found between PA and birth weight across all studies (P<0.01). In subgroup analyses, moderate PA was not significantly related to birth weight (ES=0.05; P=0.49). There was evidence of a negative relationship between vigorous PA and birth weight (ES=0.27; P<0.01) (∼150 g difference); however, significant heterogeneity precludes further interpretation, i.e., the studies included in this subgroup were too disparate to compare. Differences in maternal weight gain significantly and positively accounted for ∼17% of the variance in birth weight between moderate and vigorous exercisers (P<0.01). CONCLUSIONS Moderate physical activity performed throughout pregnancy did not affect birth weight. The impact of vigorous PA on birth weight remains unclear due to significant heterogeneity of study results.

Maternal Physical Activity And Birth Weight

The CDC/ACSM (1995) recommendations for moderate physical activity (PA) (3–5 METs, ≥30 min, ≥5 d·wk−1) in healthy adults are currently advocated for pregnant women by the American College of Obstetricians and Gynecologists (ACOG, 2002). However, further research on birth outcome may be needed before ACOG endorses theCDC/ACSM recommendations for vigorous PA (≥ 6 METs, ≥20 min, ≥3 d·wk−1) during pregnancy. PURPOSE Using meta-analysis, we examined whether the relationship between maternal PA and birth weight was moderated by PA intensity. Additionally we examined the impact of maternal weight gain on birth weight. METHODS The literature search was performed using NLM Medline, Embase, and manual searching of bibliographies. Studies were screened to ensure they included a measure of physical activity during pregnancy (with a sedentary control group) and reported birth weight as a continuous variable within the normal birth weight range. A random effects model was used to calculate the pooled effect size (ES) of birth weight by maternal PA. Pre-specified subgroups (e.g., maternal age, maternal weight gain, study design) were used to examine potential heterogeneity. Meta-regression was utilized to estimate the amount of variance in birth weight between physically active and sedentary pregnant women that can be accounted for by differences in maternal weight gain. RESULTS Of 2418 potentially relevant studies located, 23 satisfied inclusion criteria after full-text review. Study participants were mostly Caucasian, nonsmokers, and nulliparous. Significant heterogeneity was found between PA and birth weight across all studies (P<0.01). In subgroup analyses, moderate PA was not significantly related to birth weight (ES=0.05; P=0.49). There was evidence of a negative relationship between vigorous PA and birth weight (ES=0.27; P<0.01) (∼150 g difference); however, significant heterogeneity precludes further interpretation, i.e., the studies included in this subgroup were too disparate to compare. Differences in maternal weight gain significantly and positively accounted for ∼17% of the variance in birth weight between moderate and vigorous exercisers (P<0.01). CONCLUSIONS Moderate physical activity performed throughout pregnancy did not affect birth weight. The impact of vigorous PA on birth weight remains unclear due to significant heterogeneity of study results.

Maternal recreational physical activity is associated with plasma leptin concentrations in early pregnancy

A limited amount of literature suggests that plasma leptin concentrations are reduced with habitual physical activity in men and non-pregnant women. We investigated the relationship between maternal physical activity and plasma leptin during early pregnancy. The study population included 879 normotensive, non-diabetic pregnant women who reported physical activity type, frequency, and duration in early pregnancy. Plasma leptin, measured in blood samples collected <16 weeks gestation, were determined using enzyme immunoassays. Weekly duration (h/week) and energy expended on recreational physical activity [metabolic equivalent score (MET)-h/week] were categorized by tertiles among active women. Physical activity intensity was categorized as none, moderate (<6 MET) and vigorous (> or =6 MET). Differences in leptin concentrations across categories were estimated using linear regression procedures. Mean leptin was 5.8 ng/ml lower among active versus inactive women (P=0.001). Mean leptin was lower among women in the highest levels (>12.8 h/week) of time performing physical activity (-8.1 ng/ml, P<0.001) and energy expenditure (>70.4 MET-h/week) (-8.3 ng/ml, P=0.001) compared with inactive women. Leptin was inversely associated with the intensity of physical activity. Our findings are consistent with other reports suggesting an independent inverse relationship between habitual physical activity and leptin concentrations. Our findings extend the literature to include pregnant women.

Relationships Between Maternal and Child Cardiovascular Risk Factors

To obtain information about the relationship between cardiovascular and diabetic risk factors of mothers and their children and to determine whether these relationships differ by physical activity or ethnicity. Prospective study. The Texas site of the Studies of Child Activity and Nutrition Program. A 1986 to 1989 triethnic sample (European American, African American, and Hispanic) of 133 mothers and their 6- to 7-year-old children. Maternal and child fasting insulin levels; total, high-density lipoprotein, and low-density lipoprotein cholesterol levels; triglyceride levels; waist circumference; systolic and diastolic blood pressures; height; weight; and body mass index. Maternal physical activity was assessed by means of a 7-day recall. Child physical activity was assessed by heart rate monitoring. Correlational methods were used to describe the relationships among metabolic risk factors and physical activity; chi2 tests of independence were used to examine the relationships between ethnic groups. Body mass index and waist circumference were significantly (P<.05) associated among Hispanic mothers and their children, but not in other ethnic groups. Insulin, high-density lipoprotein, and low-density lipoprotein levels were significantly associated among African American mothers and their children, but not in other ethnic groups. Maternal and child physical activity were not significantly associated with any of the risk variables or each other. The relationships between the risk factors of mothers and children differed by ethnicity, but not by physical activity.

Relation between Maternal Recreational Physical Activity and Plasma Lipids in Early Pregnancy

The authors examined the relation between recreational physical activity and plasma lipid concentrations in early pregnancy. Between 1996 and 2000, 925 normotensive, nondiabetic pregnant women in Washington State were interviewed at approximately 13 weeks' gestation regarding type, frequency, and duration of physical activity during the previous 7 days. Plasma triglyceride, total cholesterol, and high density lipoprotein cholesterol concentrations were measured in contemporaneous blood samples. After adjustment, mean triglyceride concentration was 12.7 mg/dl lower in women performing any physical activity versus none (95% confidence interval (CI): -22.7, -2.6). Mean triglyceride concentration was lower in women in the highest tertiles of time performing physical activity (-23.6 mg/dl, 95% CI: -34.9, -12.2), energy expenditure (-23.6 mg/dl, 95% CI: -35.1, -12.2), and peak intensity (-18.1 mg/dl, 95% CI: -29.5, -6.8) versus inactive women. Reductions in mean total cholesterol were also observed for women with the highest levels of time performing physical activity, energy expenditure, and peak intensity. Linear relations were observed across levels of physical activity measures for triglyceride and total cholesterol. No association was found between physical activity and high density lipoprotein cholesterol. These data suggest that habitual physical activity may attenuate pregnancy-associated dyslipidemia.

11- to 15-Year-Old Children of Women Who Danced during Their Pregnancy

Aim: To determine whether high levels of maternal physical activity (dancing during pregnancy), influenced the offspring. Materials and Methods: Sixty-four women (32 of whom had continued to dance for at least 2 months after the beginning of pregnancy) filled in a questionnaire to assess the health and behavior of their offspring, now 11–15 years of age. Results: More children born from women who had continued to dance during pregnancy needed to be rocked to sleep during their first year (p < 0.05). More children in the study group played musical instruments (p < 0.05). There were no significant differences between the groups regarding other parameters. Conclusions: The greater need to be rocked to fall asleep and the attitude to play musical instruments recorded in the children of dancers may be related to prenatal maternal movement. But they may also be due to other causes as discussed.

A case-control study of maternal recreational physical activity and risk of gestational diabetes mellitus

Despite the maternal and infant morbidity associated with gestational diabetes mellitus (GDM), few modifiable risk factors have been identified. We explored the relation between recreational physical activity performed during the year before and during the first 20 weeks of pregnancy and the risk of GDM. 155 GDM cases and 386 normotensive, non-diabetic pregnant controls provided information about the type, intensity, frequency, and duration of physical activity performed during these time periods. Women who participated in any recreational physical activity during the first 20 weeks of pregnancy, as compared with inactive women, experienced a 48% reduction in risk of GDM (odds ratio [OR]=0.52; 95% confidence interval [CI] 0.33–0.80). The number of hours spent performing recreational activities and the energy expended were related to a decrease in GDM risk. No clear patterns related to distance walked and pace of walking emerged. Daily stair climbing, when compared with no stair climbing, was associated with a 49–78% reduction in GDM risk ( P for trend <0.011). Recreational physical activity performed during the year before the index pregnancy was also associated with statistically significant reductions in GDM risk, but women who engaged in physical activity during both time periods experienced the greatest reduction in risk (OR=0.40; 95% CI 0.23–0.68). These data suggest that recreational physical activity performed before and/or during pregnancy is associated with a reduced risk of GDM.

Recommended Weight Gain, Maternal Physical Activity and Fetal Growth

0284 Both maternal physical activity and weight gain have been shown to Influence birth weight. However, there is little known about how maternal weight gain, with respect to recommended levels, may affect the relationship between maternal physical activity and birth weight. PURPOSE: Our purpose was to examine the Influence of maternal physical activity, in conjunction with recommended weight gain, on fetal growth. METHODS: Women (N = 49) were studied twice during pregnancy (20 and 32 weeks gestation). Physical activity was measured for two consecutive days at each time point by Caltrac accelerometry. Length of time the accelerometers were worn, kilocalories expended during that time, and women's body weights were used to calculate average MET intensities above resting values. Average METs at both time points represented mid-late gestation maternal physical activity. Maternal weight gain from 20 to 32 weeks was determined. Subjects were categorized into prepregnancy weight for height standards (using 12 week post-partum weight as a surrogate for prepregnancy weight) based on 1983 Metropolitan Life Tables (>10% below expected weight for height (n = 7), <10% below and <20% above (n = 29), >20% above (n = 13)). Appropriate rate of weight gain between 20 and 32 weeks gestation was determined using a weight gain grid adjusted for pregravid body size (Georgia Dietetic Association, 1987). Information on birth weight and gestational age at time of delivery was obtained from medical records. Birth weight was adjusted by gestational age, sex, and parity (Zhang & Bowes 1995) in order to calculate fetal growth rate (FGR) for each infant. RESULTS: None of the women, whether gaining more or less than recommended for their body size, delivered low birth weight babies (3720±512.5 g; range 2753g-4943g). FGR increased with increased weight gain, irrespective of pregravid body size (r = 0.46; P<0.001). Physical activity during pregnancy was associated with lower FGR (r = −0.44; P<0.001). Using simple regression analysis we found that maternal physical activity predicted ∼20% of the variance in fetal growth ratio (P<0.001). When weight gain (as a percent of recommended weight gain) was added to the model, an additional 9% of the variance in FGR was explained (r2 = 0.29; P<0.001). CONCLUSION: The amount/intensity of physical activity performed during gestation is inversely related to fetal growth ratio. However, birth weight at any physical activity level was adjusted upward if women gained more weight than recommended during mid-late gestation. Supported by NIH (RO3 HD 35080)

Recommended Weight Gain, Maternal Physical Activity and Fetal Growth

0284 Both maternal physical activity and weight gain have been shown to Influence birth weight. However, there is little known about how maternal weight gain, with respect to recommended levels, may affect the relationship between maternal physical activity and birth weight. PURPOSE: Our purpose was to examine the Influence of maternal physical activity, in conjunction with recommended weight gain, on fetal growth. METHODS: Women (N = 49) were studied twice during pregnancy (20 and 32 weeks gestation). Physical activity was measured for two consecutive days at each time point by Caltrac accelerometry. Length of time the accelerometers were worn, kilocalories expended during that time, and women's body weights were used to calculate average MET intensities above resting values. Average METs at both time points represented mid-late gestation maternal physical activity. Maternal weight gain from 20 to 32 weeks was determined. Subjects were categorized into prepregnancy weight for height standards (using 12 week post-partum weight as a surrogate for prepregnancy weight) based on 1983 Metropolitan Life Tables (>10% below expected weight for height (n = 7), <10% below and <20% above (n = 29), >20% above (n = 13)). Appropriate rate of weight gain between 20 and 32 weeks gestation was determined using a weight gain grid adjusted for pregravid body size (Georgia Dietetic Association, 1987). Information on birth weight and gestational age at time of delivery was obtained from medical records. Birth weight was adjusted by gestational age, sex, and parity (Zhang & Bowes 1995) in order to calculate fetal growth rate (FGR) for each infant. RESULTS: None of the women, whether gaining more or less than recommended for their body size, delivered low birth weight babies (3720±512.5 g; range 2753g-4943g). FGR increased with increased weight gain, irrespective of pregravid body size (r = 0.46; P<0.001). Physical activity during pregnancy was associated with lower FGR (r = −0.44; P<0.001). Using simple regression analysis we found that maternal physical activity predicted ∼20% of the variance in fetal growth ratio (P<0.001). When weight gain (as a percent of recommended weight gain) was added to the model, an additional 9% of the variance in FGR was explained (r2 = 0.29; P<0.001). CONCLUSION: The amount/intensity of physical activity performed during gestation is inversely related to fetal growth ratio. However, birth weight at any physical activity level was adjusted upward if women gained more weight than recommended during mid-late gestation. Supported by NIH (RO3 HD 35080)

Prospective Study of Gestational Diabetes Mellitus Risk in Relation to Maternal Recreational Physical Activity before and during Pregnancy

Physical activity has been associated with a reduced risk of gestational diabetes mellitus, but inferences have been hampered by recall and selection bias. The authors examined the relation between recreational physical activity before and during pregnancy and risk of gestational diabetes mellitus in a prospective cohort study. In 1996-2000, 909 normotensive, nondiabetic women in Seattle and Tacoma, Washington, were questioned during early gestation about physical activity performed during the year before and 7 days prior to the interview during pregnancy. Compared with inactive women, women who participated in any physical activity during the year before experienced a 56% risk reduction (relative risk (RR) = 0.44, 95% confidence interval (CI): 0.21, 0.91). Women spending >/=4.2 hours/week engaged in physical activity experienced a 76% reduction in gestational diabetes mellitus risk (RR = 0.24, 95% CI: 0.10, 0.64), and those expending >/=21.1 metabolic equivalent-hours/week experienced a 74% reduction (RR = 0.26, 95% CI: 0.10, 0.65) compared with inactive women. Physical activity during pregnancy was also associated with reductions in gestational diabetes mellitus risk. Women who engaged in physical activity during both time periods experienced a 69% reduced risk (RR = 0.31, 95% CI: 0.12, 0.79). Findings suggest that efforts to increase maternal physical activity may contribute to substantial reductions in gestational diabetes mellitus risk.

Women's behaviour, beliefs and information sources about physical exercise in pregnancy

Objective: to examine the potential effect of low-risk pregnancy on women's recreational activity patterns and to explore pregnant women's beliefs and information sources regarding physical exercise participation. Design: preliminary, prospective survey Setting: participants’ homes in the East Midlands, UK. Participants: fifty-seven nulliparous, pregnant women. Measurements: levels of maternal physical activity participation were assessed by semi-structured interview at 16, 25, 34 and 38 weeks gestation. The modified Baecke questionnaire provided a measure of women's habitual sport and leisure activities in the 12 months prior to pregnancy. A 10-item scale assessed maternal beliefs regarding the importance of physical activity in pregnancy. The fetal health locus of control scale measured the extent to which women believed their own behaviour, the behaviour of others and/or chance would influence fetal health. Open-ended questions assessed women's information sources. Findings: fourteen of the 36 (39%) women who reported participating in some form of weekly exercise before pregnancy did not report pursuing any similar activities during pregnancy. Rest and relaxation were perceived as being significantly more important during pregnancy than was regular exercise or the maintenance of an active lifestyle. Fifty-five respondents (96%) indicated that they had received advice about physical activity at least once during pregnancy. At 16 weeks gestation, women obtained most of their information from books and magazines. Between 25 and 38 weeks gestation, most advice came from family and friends. Participants who reported receiving this advice were significantly older, more educated and of a higher activity level pre-pregnancy. Key conclusions: levels of maternal exercise may decline during pregnancy both as a result of the physical changes of pregnancy and from a combination of social and psychological factors. Present health education may be failing to correct inaccurate perceptions of the risks associated with physical exercise in pregnancy. Implications for practice: improving the quantity and quality of information related to physical exercise has the potential to correct inaccurate perceptions and confer several benefits on maternal and fetal health. Effective intervention strategies should focus not only on the pregnant woman but also extend to her family, friends and exercise provider.

PTH/PTHrP activity and the programming of skeletal development in utero.

There is increasing evidence that nutritional deficiency in utero adversely affects bone development and the risk of developing osteoporosis in later life. Although the mechanisms involved are unknown, circumstantial evidence points to an important role of PTH/PTHrP activity. It is recognized that PTH and PTHrP are critically involved in regulating fetal calcium homeostasis, actions that are mediated at least in part by PPR. As well as playing a central role in the maintenance of calcium homeostasis in the fetus, studies in transgenic mice show that PTH, PTHrP, and PPR exert similar effects on skeletal development in utero, acting to increase the size of the trabecular envelope and decrease that of the cortical envelopes. Taken together, these observations raise the possibility that stimulation of PTH/PTHrP activity in the fetus in response to calcium deficiency acts to increase the size of the trabecular envelope but to reduce that of the cortical envelope. Although any increase in trabecular bone at birth is likely to be relatively transient, a decrease in size of the cortical envelope may have a persistent effect on the trajectory of bone growth in subsequent childhood. Consistent with this proposal, preliminary findings from birth cohort studies suggest that maternal calcium intake and cord blood calcium levels are positively related to bone mass of the offspring as assessed later in childhood. Further studies are justified to determine whether alterations in fetal PTH/ PTHrP activity caused by calcium stress lead to a reduction in size of the cortical envelope at birth that persists into childhood and later adult life and to identify modifiable maternal factors that are responsible for these changes.

Umbilical venous IGF-1 concentration, neonatal bone mass, and body composition.

IGF-1 is a key growth factor during fetal life. Using DXA, we found that the concentration of IGF-1 in umbilical cord serum is strongly related to neonatal whole body bone mineral content, lean mass, and fat mass. However IGF-1 did not explain the relationships of maternal smoking, fat mass, and physical activity with neonatal bone mass. The study supports a direct role for circulating IGF-1 in growth of the fetal skeleton. Evidence is accumulating that the risk of osteoporosis in later life may be determined in part by environmental influences during intrauterine and early postnatal life. We previously reported that maternal birthweight, smoking, fat stores, and physical activity during pregnancy predict neonatal bone mass. While the growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis is an important determinant of postnatal skeletal growth, there are few data relating the concentration of growth factors in umbilical cord blood to bone mineral content (BMC) and other indices of body composition in the newborn infant. We conducted a population-based study in a cohort of full-term, newborn infants whose mothers were characterized for lifestyle, body composition, and nutrition through their normal pregnancies. In a sample of 119 infants from the cohort, we related cord serum IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 concentrations to neonatal body composition measured by DXA and evaluated the extent to which this cytokine mediates the previously reported effects of maternal diet and lifestyle on neonatal bone mass. There were strong positive associations between cord serum IGF-1 concentration and whole body BMC (r = 0.38, p < 0.001), whole body lean mass (r = 0.40, p < 0.001), and whole body fat mass (r = 0.50, p < 0.001) after adjusting for gestational age and sex. There was no association between cord serum IGF-1 and BMC adjusted for bone size. Neither cord serum IGF-1 nor IGFBP-3 explained the relationships that we previously reported between maternal influences and neonatal bone mass. Cord serum IGF-1 is more closely related to the size of the neonatal skeleton than to its degree of mineralization. Documented maternal determinants of neonatal bone mass seem to mediate their effects independently of variations in cord serum IGF-1 in healthy pregnancies.

Prenatal and childhood influences on osteoporosis.

Osteoporosis is a major cause of morbidity and mortality through its association with age-related fractures. Although most effort in fracture prevention has been directed at retarding the rate of age-related bone loss, and reducing the frequency and severity of trauma among elderly people, evidence is growing that peak bone mass is an important contributor to bone strength during later life. The normal patterns of skeletal growth have been well characterized in cross-sectional and longitudinal studies. It has been confirmed that boys have higher bone mineral content, but not volumetric bone density, than girls. Furthermore, in both genders there is a dissociation between the peak velocities for height gain and bone mineral accrual. Puberty is the period during which volumetric density appears to increase in both axial and appendicular sites. Many factors influence the accumulation of bone mineral during childhood and adolescence, including heredity, gender, diet, physical activity, endocrine status and sporadic risk factors such as cigarette smoking. Measures for maximizing bone mineral acquisition, particularly through encouraging physical activity and adequate dietary calcium intake, are likely to affect the risk of fracture in later generations. In addition to these modifiable factors during childhood, evidence has also accrued that the risk of fracture might be programmed during intrauterine life. Epidemiological studies have demonstrated a relationship between birthweight, weight in infancy and adult bone mass. This appears to be mediated through modulation of the set-point for basal activity of pituitary-dependent endocrine systems such as the hypothalamic - pitutiary - adrenal (HPA) and growth hormone/insulin-like growth factor I (GH/IGF-I) axes. Maternal smoking, diet and physical activity levels appear to modulate bone mineral acquisition during intrauterine life; furthermore, both low birth size and poor childhood growth are directly linked to the later risk of hip fracture. The optimization of maternal nutrition and intrauterine growth should also be included within preventive strategies against osteoporotic fracture, albeit for future generations.

Physical activity and risk of neural tube defects.

Owing to its association with known risk factors for neural tube defects (NTDs) and its impact on physiologic processes relevant to fetal development, physical activity was identified as a potential risk factor for NTD-affected pregnancy. Using data from a population-based case-control study of deliveries occurring in California from 1989 to 1991, we estimated the potential risk of having an NTD-affected pregnancy associated with variation in maternal physical activity. In-person interviews were conducted with 538 (88% of eligible) mothers of NTD cases and with mothers of 539 (88%) nonmalformed controls on average 5 months from the term delivery date. An index reflecting reported frequency and exertion level for six activity groups (e.g., jogging and running) was used to summarize each woman's physical activity level in the periconceptional period. Unadjusted analyses indicated that compared to women considered inactive by this index, physically active women had 30-50% lower risk for NTD-affected pregnancies. After adjustment for several potential confounders and an evaluation of potential effect modification, results suggested that the association was restricted to women who did not take multivitamin/mineral supplements during the periconceptional period. Excluding mothers with reported medical problems did not substantially alter findings. This study suggests that the benefits of physical activity may extend to reduction of NTD risk among certain subgroups of women.

Relationship between maternal physical activities and preterm birth.

A cross-sectional study was conducted in three Municipal Health Centers located in Aichi prefecture, central Japan. The main purpose of this study was to verify the interaction between maternal leisure-time physical activities prior to and/or during pregnancy and preterm birth and also, to determine the risk factors related to preterm birth. In this study of the 2,682 questionnaires delivered within one year to mothers or relatives at the Municipal Health Centers, 1,714 questionnaires were analyzed. In a univariate analysis the results showed that mothers who had a previous low birthweight or a premature baby, or who were hospitalized during pregnancy before the 37(th) week of gestation, or had an occupational activity, or carried out their household chores, or were sick, or received much medical advice and did not exercise were more likely to have a preterm baby. In multivariable logistic regression analyses, maternal hospitalization before the 37(th) week of gestation and occupational activities were significant determinants associated with preterm birth. Thus, it was verified that maternal leisure-time physical activities prior to and/or during pregnancy were not related to preterm birth.

Relationship between Maternal Physical Activities and Preterm Birth.

Relationship between Maternal Physical Activities and Preterm Birth.

Maternal leisure-time physical activities are not determinant risk factors of low birthweight babies: A cross-sectional study of 1,714 pregnant women

There is a general recognition of the role of low birthweight (LBW) as a major determinant of infant mortality rates. Since the rate of LBW has been increasing over the past fifteen years in Japan, we decided to ascertain the risk factors related to it, and also to verify whether or not maternal leisure-time physical activities including sports activities, before pregnancy and during gestation, affected the rate of LBW babies. In our study of the 2,682 questionnaires delivered within a year to the Municipal Health Centers of the three cities chosen for this study, 1,714 questionnaires were analyzed. The results in a univariate analysis showed that maternal height, pre-pregnancy weight, length of gestation, smoking, hospitalization before the 37th week of gestation, a history of LBW, and occupational activities were significantly associated with LBW. In logistic regression analyses, mothers of smaller stature, less pre-pregnancy weight, less length of gestation and mothers who were, furthermore, hospitalized before the 37th week of gestation, smoked, had previously delivered a LBW baby or had experienced stressful events during pregnancy were more likely to have LBW babies. The results showed that maternal leisure-time physical activities before and/or during pregnancy had no bearing on the delivery of a LBW baby.

Physiology of pregnancy and nutrient metabolism

Pregnancy consists of a series of small, continuous physiologic adjustments that affect the metabolism of all nutrients. The adjustments undoubtedly vary widely from woman to woman depending on her prepregnancy nutrition, genetic determinants of fetal size, and maternal lifestyle behavior. Studies of protein and energy metabolism illustrate the potential of adjusting the use of those nutrients to conserve a fetal supply. Adjustments in the metabolism of nitrogenous compounds are in place by the second quarter of pregnancy. During the last quarter of pregnancy, when fetal demands are greatest, those adjustments allow a positive nitrogen retention. The energy requirement of basal metabolism is influenced by maternal prepregnant nutrition and by fetal size. If maternal energy reserves are low at conception, the basal metabolic rate is down-regulated to conserve energy. Also, women having larger babies tend to have greater increases in their basal metabolic rate and lower rates of maternal energy storage. Changes in maternal food and physical activity behaviors during gestation may augment the physiologic adjustments. However, the substantial variability in food intakes and physical activity makes it difficult to show those changes. Thresholds in the capacity to adjust nutrient use to the amount supplied exist for all nutrients. When intakes fall below the threshold, fetal growth and development is affected more than is maternal health. Efforts to achieve good maternal nutritional status preconception as well as throughout gestation best assure a good milieu for fetal growth and development.

Maternal Leisure-time Physical Activities are not Determinant Risk Factors of Low Birthweight Babies. A Cross-sectional Study of 1,714 Pregnant Women.

Maternal Leisure-time Physical Activities are not Determinant Risk Factors of Low Birthweight Babies. A Cross-sectional Study of 1,714 Pregnant Women.