Postpartum Body Mass Research Articles

Heterogeneity of glycometabolism in patients with gestational diabetes mellitus: Retrospective study of 1,683 pregnant women.

Aims/IntroductionTo evaluate the glycometabolism and outcomes of gestational diabetes mellitus (GDM) patients according to the International Association of Diabetes and Pregnancy Study Group (IADPSG) criteria in China.Materials and MethodsAccording to the results of a 75‐g oral glucose tolerance test, 1,683 pregnant women were divided into three groups: (i) an increment GDM group (patients meet the IADPSG criteria, but not the previous Chinese criteria); (ii) a stock GDM group (patients meet both criteria); and (iii) a normal glucose tolerance group. Their glycometabolism outcomes, prepregnancy and postpartum body mass index were compared, as were maternal–fetal outcomes.ResultsThe IADPSG and previous Chinese criteria diagnosed 12.4% and 5.5% of women with GDM. Pairwise comparison showed significant differences in 1‐h plasma glucose, 2‐h plasma glucose, HbA1c values and area under curve of glucose among all groups (P < 0.01). The fasting plasma glucose and postpartum body mass index of the stock group were significantly higher than those of the other two groups (P < 0.01). The incidences of hypertensive disorder complicating pregnancy and cesarean section of the normal glucose tolerance group were significantly lower than those of the other two groups (P < 0.001). No significant differences in patient age, prepregnancy body mass index, duration of pregnancy, prevalence of premature labor, premature rupture of membranes, neonatal jaundice, neonatal asphyxia or Ponderal Index were observed, but significant differences in macrosomia and neonatal hypoglycemia were observed (P < 0.05).ConclusionsThe IADPSG criteria doubled the number of GDM patients. The cases of the increment patients were mild. The IADPSG criteria should be discussed fully before implementation in China.

The association between maternal nutrition and lifestyle during pregnancy and 2-year-old offspring adiposity: analysis from the ROLO study

AimTo examine the association between maternal nutrition and lifestyle factors and offspring adiposity, using baseline and 2-year postpartum follow-up data from a randomised control trial of low glycaemic index diet.Subject and methodsFood diaries and lifestyle questionnaires were completed during pregnancy and infant feeding and maternal lifestyle questionnaires 2 years postpartum for 281 mother and infant pairs from the ROLO study. Maternal anthropometry was measured throughout pregnancy and infant and maternal anthropometry was measured 2 years postpartum.ResultsMaternal 2 year postpartum body mass index (BMI) was positively associated with offspring BMI-for-age z-score (B = 0.105, p = 0.015). Trimester 2 saturated fat intake was positively associated with offspring subscapular:triceps skinfold ratio (B = 0.018, p = 0.001). Trimester 1 glycaemic index was also positively associated with offspring sum of subscapular and triceps skinfolds (B = 0.009, p = 0.029).ConclusionsMaternal BMI 2 years postpartum was positively associated with offspring BMI. Pregnancy saturated fat intake was positively and polyunsaturated fat negatively associated with offspring adiposity. While further research is necessary, pregnancy and the postpartum period may be early opportunities to combat childhood obesity.Electronic supplementary materialThe online version of this article (doi:10.1007/s10389-016-0740-9) contains supplementary material, which is available to authorized users.

A novel system dynamics model of female obesity and fertility.

Our objective was to create a system dynamics model specific to weight gain and obesity in women of reproductive age that could inform future health policies and have the potential for use in preconception interventions targeting obese women. We used our system dynamics model of obesity in women to test various strategies for family building, including ovulation induction versus weight loss to improve ovulation. Outcomes included relative fecundability, postpartum body mass index, and mortality. Our system dynamics model demonstrated that obese women who become pregnant exhibit increasing obesity levels over time with elevated morbidity and mortality. Alternatively, obese women who lose weight prior to pregnancy have improved reproductive outcomes but may risk an age-related decline in fertility, which can affect overall family size. Our model highlights important public health issues regarding obesity in women of reproductive age. The model may be useful in preconception counseling of obese women who are attempting to balance the competing risks associated with age-related declines in fertility and clinically meaningful weight loss.

Dietary polyunsaturated fatty acid intake during late pregnancy affects fatty acid composition of mature breast milk

ObjectiveThe aim of this study was to investigate how maternal polyunsaturated fatty acid intake at different periods during pregnancy affects the composition of polyunsaturated fatty acids in mature human milk. MethodsA prospective study was conducted involving 45 pregnant women, aged between 18 and 35 y, who had full-term pregnancies and practiced exclusive or predominant breast-feeding. Mature breast milk samples were collected after the 5th postpartum week by manual expression; fatty acid composition was determined by gas chromatography. Fatty acid intake during pregnancy and puerperium was estimated through multiple 24-h dietary recalls. Linear regression models, adjusted by postpartum body mass index and deattenuated, were used to determine associations between estimated fatty acids in maternal diet during each trimester of pregnancy and fatty acid content in mature human milk. ResultsA positive association was identified between maternal intake of eicosapentaenoic acid (β, 1.873; 95% confidence interval [CI], 0.545, 3.203) and docosahexaenoic acid (β, 0.464; 95% CI, 0.212–0.714) during the third trimester of pregnancy, as well as the maternal dietary ω-3 to ω-6 ratio (β, 0.093; 95% CI, 0.016–0.170) during the second and third trimesters and postpartum period, with these fatty acids content in mature breast milk. ConclusionsThe maternal dietary docosahexaenoic acid and eicosapentaenoic acid content during late pregnancy may affect the fatty acid composition of mature breast milk. Additionally, the maternal dietary intake of ω-3 to ω-6 fatty acid ratio, during late pregnancy and the postpartum period, can affect the polyunsaturated fatty acid composition of breast milk.

Body Image Among Turkish Women During the First Year Postpartum

In this study, we investigated the body image of Turkish women in their first year postpartum. We recruited 440 postpartum women who had applied to the outpatient clinics of the Maternity and Children's Hospital in the city of Ordu, Turkey. The mean of the women's body image scores was over the “middle level.” The women's body image scale (BIS) score showed a significant negative relation with age, number of births, weight before pregnancy, weight gain, during pregnancy, weight soon after childbirth, present weight, postpartum weight gain, and postpartum body mass index (BMI).

Timing of Stage II Lactogenesis Is Predicted by Antenatal Metabolic Health in a Cohort of Primiparas

Time to onset of stage II lactogenesis varies widely, and delayed onset of lactogenesis (OL) is common among first-time mothers in the United States. Higher body mass index, older age, and larger infant birth weight are identified risk factors for delayed OL; all are known correlates with glucose metabolism. Our objective was to prenatally assess maternal biomarkers related to metabolic health and determine the extent to which these biomarkers predict timing of OL. We enrolled a population-based sample of expectant primiparas attending a single prenatal clinic. We obtained a blood sample 1-hour post-glucose load from an antenatal oral glucose challenge test and assayed for the following biomarkers: serum insulin, glucose, adiponectin, leptin, C-reactive protein, interleukin-6, resistin, and tumor necrosis factor-α. Our outcome measure was timing of OL, based on maternal report at 3-5 days postpartum. We used linear regression to model OL hour. Twenty-six of 29 (90%) agreed to screening, 18 delivered at term and initiated breastfeeding, and 16 have complete data. Median (minimum-maximum) postpartum body mass index was 27.4 (21.8-34.7) kg/m(2), and median time to OL was 64 (10-121) hours. The model, OL = 232 - 34.9(ln[ratio insulin/glucose]) - 1.4(adiponectin), explained 56% of the variation in OL hour (p = 0.005) and was not weakened by potential confounders. Higher serum insulin secretion relative to serum glucose after a glucose challenge and higher serum adiponectin are associated with earlier onset of OL. These findings suggest that factors associated with better glucose tolerance predict earlier OL.

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Interventions to Increase the Duration of Breastfeeding in Obese Mothers: The Bassett Improving Breastfeeding Study

Maternal obesity is associated with poor breastfeeding outcomes, yet no intervention has been developed to improve them. To ascertain whether increased breastfeeding support or provision of a breast pump is a feasible, effective intervention to improve breastfeeding, we enrolled obese women who intended to breastfeed in two randomized trials. In Bassett Improving Breastfeeding Study (BIBS) 1, 40 women received targeted breastfeeding support in the hospital and via telephone or usual care. Information regarding breastfeeding was collected via telephone for 7 days after delivery and at 30 and 90 days postpartum. In BIBS 2, 34 obese mothers received a manual or electric breast pump to use for 10-14 days or no pump; data collection was similar. In both experiments, randomization failed to distribute women of differing postpartum body mass index adequately among the treatment groups. When analyses were adjusted for this, there was no difference in BIBS 1 between targeted and usual care groups and in BIBS 2 among the treatment groups in the proportion of women still breastfeeding at the times studied. In future studies of obese women, stratified randomization may be necessary. Further development of interventions to help obese women achieve optimal breastfeeding outcomes is required.

Maternal Stress, Physical Activity, and Body Mass Index During New Mothers' First Year Postpartum

We evaluated associations of parenting stress, including depressive symptoms, with 51 first-time mothers' light and moderate physical activity and body mass index during the first year postpartum. The Parenting Stress Index and 24-hour physical activity recalls were completed during the first year postpartum (mean time elapsed since birth: 6 months). Direct relationships between identified variables were tested, and then hierarchical linear regression was used to assess hypothesized relationships among body mass index, physical activity, and parenting stress. Effects of parenting stress on the relationships between postpartum body mass index, light physical activity, and moderate physical activity were evaluated after controlling for factors known to be associated with overweight and low levels of physical activity in women. Mean postpartum body mass index = 27.4 kg/m2 ± 7.7, range = 18–50 kg/m2. Mean reported hours of light physical activity = 11.2 ± 3.0, and moderate physical activity = 4.5 ± 3.0 per day. Postpartum body mass index was not associated with parenting stress, but was positively related to higher pre-pregnancy body mass index (r = .89, p < .01) and light physical activity (r = .32, p < .05), and was negatively related to moderate physical activity (r = −25, p < .08). Higher postpartum body mass index (β = .27, p < .05), less concern regarding parenting competence (β = −.95, p < .001), and more depressive symptoms (β = .66, p < .01) were associated with more light physical activity (R2 = .48, p < .001). More moderate physical activity (R2 = .45, p < .001) was associated with lower postpartum body mass index (β = −.27, p < .05), more concern about parenting competence (β = 1.0, p < .001), and less depressive symptoms (β = −.68, p < .01). Higher postpartum body mass index (R2 = .89, p < .001) was associated with higher pre-pregnancy body mass index (β = .99, p < .001), more pregnancy weight gain (β = .22, p < .001), less attachment (β = −.68, p < .01), and less social isolation (β = −.13, p < .02). These data suggest that interventions that target parenting stress and depressive symptoms in addition to physical activity are needed to prevent development of overweight in new mothers.

Family matters: Maternal and litter-size effects on immune parameters in young laboratory rats

A functional immune system is important for the survival of mammalian young, particularly at weaning when they lose the immunological support provided by the mother’s colostrum and milk. In altricial mammals, litter size and maternal characteristics are important components of an animal’s early environment, which affect postnatal growth and development. In a study of unculled litters of Long-Evans laboratory rats ( Rattus norvegicus), we asked whether such parameters are also associated with the immune status of the young shortly before weaning. On postnatal day 17, we assessed numbers of several leukocyte and lymphocyte subsets, the activity of the complement system, and immunoglobulin G (IgG) concentrations in the serum. Averaging the values of all pups per litter, we found negative correlations between litter size and lymphocyte counts, complement system activity and IgG concentration. Maternal effects were seen in the positive correlation between maternal postpartum body mass and granulocyte and monocyte counts. In addition, lymphocyte and monocyte counts as well as complement activity were lower for the young of multiparous than of primiparous mothers. This suggests a trend towards a better developed immune system in such offspring, which may be relevant for their immediate and long-term survival. The effects described here have potential implications for the design and interpretation of biomedical studies of immune parameters in laboratory rats.

Cord Blood Lipids in Infants Born to HIV-1-Infected Women Treated with Combination Antiretroviral Therapy

To investigate the effect of exposure to protease inhibitor (PI) therapy in utero on cord blood lipids in infants born to mothers enrolled in AIDS Clinical Trials Group protocol 5084, a prospective, multicentre, observational study of antiretroviral therapy (ART) during pregnancy. Clinical outcome was determined in 80 infants born to women treated with PIs and 73 infants born to women treated with other antiretrovirals during pregnancy. Cord blood serum from 117 of these infants was assayed for total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol, triglyceride, apolipoprotein A1 (apoA1), apolipoprotein B100 (apoB) and lipoprotein (a). Covariates considered in the analysis included race/ethnicity, gestational age, infant gender, infant birth weight, mode of delivery, maternal tobacco and alcohol use, post-partum body mass index, and ART duration. Cord blood total and HDL cholesterol, triglyceride, apoA1, apoB, lipoprotein (a) and apoB/apoA1 ratio were not different between the two groups. Cord blood lipid levels in these HIV-exposed infants were similar to those reported in other neonatal cohorts. Controlling for race/ethnicity, infants born to women treated with PIs had higher LDL cholesterol than those born to women not treated with PIs (29 mg/dl versus 27 mg/dl, P = 0.006). Only LDL cholesterol was significantly higher in the cord blood of PI-exposed infants versus those not exposed to PIs in utero. As the difference between the two groups was small, the clinical relevance of the effect of maternal PI treatment on infant LDL cholesterol levels at birth is not clear.

Optimal litter size for individual growth of European rabbit pups depends on their thermal environment

In altricial mammals and birds, the presence of a large number of litter or brood mates often affects the development of individual offspring by reducing the share of resources provided by the parents. However, sibling presence can also be favourable, conferring thermoregulatory benefits when ambient temperatures are low. Consequently, shifts in the relation between costs and benefits of sibling presence can be expected as a function of the thermal environment. In a study of a European rabbit population (Oryctolagus cuniculus) living in a field enclosure, we investigated the effects of litter size and soil temperature on pup growth over 7 years. Temperatures inside the subterranean nests were positively correlated with soil temperature and with litter size. Soil temperature varied strongly across the breeding season, ranging from 3 to 21 degrees C. Under warmer soil temperature conditions (10-15 degrees C and >15 degrees C), pup growth decreased with increasing litter size, where litters of two pups (smallest litter size considered) showed the highest growth rates. In contrast, under colder soil temperature conditions (<10 degrees C), the highest growth rates were found in litters of three pups. We also asked if such temperature-dependent differences in the optimal pup growth rates might be explained by differences in maternal characteristics, which might affect lactational performance. We assessed maternal performance using females' postpartum body mass and social rank. However, we did not find consistent differences in maternal characteristics between females giving birth to different-sized litters during different soil temperature conditions, which would have provided an alternative explanation for the observed differences in litter size-dependent pup growth. We conclude that under colder soil temperature conditions, the thermal benefits of a greater number of littermates outweigh the negative consequences of competition for milk, leading to an environment-dependent shift in the optimal litter size for individual growth in this species.

Activity levels in pregnant New Zealand women: relationship with socioeconomic factors, well-being, anthropometric measures, and birth outcome

Activity during pregnancy has health implications for mother and child. The aim of this prospective cohort study was to examine changes in activity levels during pregnancy; the influence of socioeconomic factors and well-being on activity, and the influence of activity on maternal anthropometric measures and birth outcome. Twenty-four hour activity diaries were collected for 3 d in months 4 and 7 of pregnancy in 197 volunteers. Anthropometric measures and questionnaires to determine personal details were collected at these times and 2 months post-partum. Health records were used to supply infant measures. The time spent on each activity category was calculated, and used to calculate overall daily metabolic equivalents (METs). Low socioeconomic (SES) group 24 h activity levels were significantly higher than for high SES or welfare groups (p = 0.013). Activity declined throughout pregnancy in all groups (p = 0.002). Women with children had higher 24 h activity, spending 41% more time walking and (or) on housework than nulliparous women (p = 0.013). Reduced well-being was associated with lower levels of activity. Sleep and lying down time influenced 2 month post-partum body mass (upper quartile gained 2.54 kg, lower quartile lost 0.24 kg, p < 0.001). Mean infant gestational age increased with increasing 24 h activity (p = 0.047). No infants were born prematurely to mothers who spent more than 190 min/d walking or doing housework activities in month 4. Probability of infant admission to the neonatal intensive care unit (NICU) declined with time spent walking or doing housework in month 4 (p = 0.007). Mean (SE) birth weight was 3883 (+/-165) g in the 10% of women spending less than 530 min sleeping or lying down per day, compared with 3413 (+/-104) g in the 10% of women spending 725 min or more sleeping or lying down. Socioeconomic factors were therefore important influences on activity levels during pregnancy. Inactivity, especially in early pregnancy, was associated with more maternal weight retention at 2 months post-partum and a greater probability of admission to NICU and premature delivery.

Trajectory of Weight Changes in the First 6 Weeks Postpartum

To determine the trajectory of postpartum weight changes and to examine associations between weight change in the first 6 weeks postpartum and demographic, clinical, psychosocial, and behavioral variables. Prospective, longitudinal design. Community hospital and university research setting. 26 low-income women (9 White, 8 Black, and 9 Hispanic) with uncomplicated term pregnancies. Body mass index measured weekly. Among White women, body mass index decreased significantly for the first 3 weeks of the postpartum period. Black women experienced a significant reduction in body mass index for only the first 2 postpartum weeks. Similarly, the postpartum body mass index decreased for the first 2 weeks for Hispanic women. Prepregnancy body mass index and gestational weight gain each had a significant positive effect on postpartum body mass index. Perception of social support at 4 weeks had a significant positive effect on postpartum body mass index in Black women. The trajectory of weight change was nonlinear with large initial weight losses during the first 2 to 3 weeks postpartum followed by weight plateaus for the remainder of the first 6 weeks postpartum.

Gestation temperature affects sexual phenotype, morphology, locomotor performance, and growth of neonatal brown forest skinks, Sphenomorphus indicus

We maintained pregnant Sphenomorphus indicus under four thermal conditions for the whole gestation period to assess the effects of gestation temperature on offspring phenotypes. Parturition occurred between late June and early August, with females at high body temperatures giving birth earlier than those maintained at low body temperatures. Litter size, litter mass, and postpartum body mass did not differ among treatments, and females with relatively higher fecundity produced smaller offspring. Females gave birth to predominantly female offspring (85.7% of the 14 sexed offspring were females) at 24 °C and to predominantly male offspring (76.5% of the 17 sexed offspring were males) at 28 °C. Females with the opportunity to regulate body temperature produced a mix of sexes that did not differ from equality. Offspring produced in different treatments differed in head size, hind-limb length, and tympanum length, but not in snout-vent length, tail length, body mass, fore-limb length, and eye length. Offspring produced at 28 °C were not only smaller in head size, but also shorter in hind-limb length and tympanum length than those offspring produced at lower temperatures. Offspring produced at 28 °C performed more poorly in the racetrack and grew more slowly than offspring produced in the other three treatments. Taken together, our results show that S. indicus might be a temperature-dependent sex determination species and that offspring phenotypes are impaired at high gestation temperatures but maximized at relatively low gestation temperatures.

Weight and Behavioral and Psychosocial Factors Among Ethnically Diverse, Low-Income Women After Childbirth: II. Trends and Correlates

ABSTRACT Objective: This paper presents a longitudinal analysis of behavioral and psychosocial correlates of weight trends during the first postpartum year. Data are derived from the Austin New Mothers Study (ANMS), a longitudinal study of a low-income, tri-ethnic sample of postpartum women that incorporated serial assessment of weight and behavioral and psychosocial variables. Method: Postpartum body mass index (BMI) was measured prospectively (post-delivery, 6 weeks, and 3, 6, and 12 months postpartum). The analytic sample consisted of 382 White, African American, and Hispanic women receiving maternity care funded by Medicaid who had at least three measured postpartum weights. Behavioral and psychosocial variables included energy intakes, fat intakes, physical activity, health-related lifestyle, smoking, breastfeeding, contraception, depressive symptoms, emotional eating, body image, and weight-related distress. Results: Using hierarchical linear modeling to incorporate baseline only and time-varying effects, significant associations with postpartum BMI were found for the following variables: ethnicity (p = .001), time of weight measurement (p < .001), the interaction of ethnicity and time (p = .005), prepregnant BMI (p < .001), gestational weight gain (p < .001), weight-related distress (p < .001), and energy intakes (p = .005). After adjusting for covariates, ethnic groups displayed differing trends in postpartum BMI resulting in White women having significantly lower BMIs at 12 months postpartum compared to ethnic minority women (p's < .01). Conclusion: Behavioral and psychosocial variables contribute to a fuller understanding of BMI status of low-income women during the first postpartum year.

Lactational amenorrhea is associated with child age at the time of introduction of complementary food: a prospective cohort study in rural Senegal, West Africa

In Africa, lactational amenorrhea is the major reason for birth spacing. We studied whether the early introduction of complementary food to infants is associated with an increased risk of menstruation resumption in rural African women. Senegalese women (n = 855) were included at 2-3 mo postpartum and followed up at 4-5 and 6-7 mo in dispensaries. A subsample of 502 women were followed up at 9-10 mo and twice yearly at home thereafter. Risk factors for menstruation resumption were assessed with logistic regression, with control for maternal parity, occupation, education, postpartum body mass index, child sex and weight-for-age, and season. The risk of menstruation resumption was 4.2% (95% CI: 2.8%, 5.6%) at 6-7 mo and 6.5% (4.0%, 8.9%) at 9-10 mo. Compared with the introduction of complementary food after 6-7 mo, introduction at 2-3, 4-5, or 6-7 mo was associated with a greater odds of menstruation resumption at 6-7 mo [odds ratios (ORs): 5.08 (1.01, 25.5), 6.00 (1.29, 27.4), and 4.45 (0.96, 20.6; NS), respectively]. Introduction of food at 4-5 or 6-7 mo compared with that after 6-7 mo was associated with significantly greater odds of menstruation resumption at 6-7 mo (5.13; 1.16, 22.6) but not at 9-10 mo (3.07; 0.65, 14.4; NS) or year 2. Child age at introduction of complementary food was significantly associated with the odds of menstruation resumption at 6-7 mo postpartum.

13C]Linoleic acid oxidation and transfer into milk in stunted lactating women with contrasting body mass indexes

The fat concentration of human milk is associated with maternal adiposity, but there is no clear understanding of the mechanisms controlling milk fat concentration. We evaluated the effect of postpartum body mass index (BMI; in kg/m(2)) on the metabolic distribution of an oral dose of [13C]linoleic acid in lactating women. Ten lactating women stratified by BMI (either <22.5 or >23.5) at 5 mo postpartum received orally 2.5 mg [13C]linoleic acid/kg body wt. Exhaled air, milk, and plasma samples were collected in relation to tracer administration. Linoleic acid was determined by gas chromatography. Dietary intake, serum, milk composition, [13C]linoleic acid enrichment in milk and plasma, and exhaled 13CO2 (by isotope ratio mass spectrometry) were assessed. Women with a higher BMI exhaled more 13CO2 than did women with a lower BMI (22.8 +/- 9.4% compared with 8.6 +/- 3.5% of dose, P < 0.03). Cumulated 72-h transfer of [13C]linoleic acid to milk was not significantly different between groups (14.8 +/- 6.5% compared with 17.7 +/- 6.7% of dose). Within the first 9 h after dose administration, 51.6 +/- 4.9% of the total isotope transfer into milk had passed in women with a higher BMI, but only 24.0 +/- 15.3% had passed in those with a lower BMI (P = 0.02). Women with a lower BMI, who were reputed as having less body fat, oxidized and secreted into milk less dietary linoleic acid within 12 h after tracer administration than did women with a higher BMI. In both groups, a large proportion of [13C]linoleic was retained in the maternal compartment, most likely fat tissue, in a slow turnover pool, and released slowly in later hours.

Foraging effort, food intake and lactation performance depend on maternal mass in a small phocid seal

Summary Female mammals increase energy expenditure during lactation to support the high cost of milk production. The extent to which lactation in a small phocid species, the Harbour Seal Phoca vitulina L., was fuelled by food vs body stores, how this allocation varied with maternal body mass and the consequences of maternal expenditure on offspring growth were studied. The proportional body composition of 30 females was independent of initial postpartum body mass, but larger females had absolutely more stored energy than smaller ones. Females lost 32% of postpartum body mass and 62% of body energy by late lactation; 97% of energy loss was derived from body fat. Percentage loss of body energy was independent of initial body mass, indicating that females limit their allocation of body stores to offspring by expending a constant proportion of stores rather than a constant amount. Females spent more time diving and individual dives were deeper and longer as lactation progressed. By late lactation, these characteristics of diving were inversely proportional with initial postpartum mass. During early lactation, female expenditures were covered mainly by a reduction in body energy stores. By late lactation, food intake increased six‐fold but the extent of this increase varied inversely with postpartum mass. Pup growth rate and weaning mass were positively related to postpartum mass and total daily energy expenditure of females, but were independent of the source of energy used by females during lactation. Pups of heavy females had higher survival than pups of light females. Our results support the hypothesis that maternal body mass is an important determinant of lactation strategies in pinnipeds.

MATERNAL EFFECTS ON OFFSPRING MASS AND STAGE OF DEVELOPMENT AT BIRTH IN THE HARBOR SEAL,PHOCA VITULINA

We studied effects of maternal age, body mass, and parturition date on birth mass and stage of development at birth in harbor seals (Phoca vitulina) on Sable Island, Nova Scotia, over a 10-year period. As predicted, effects of maternal mass and age on pup traits varied with maternal age. Premature pups, characterized by extensive fetal pelage termed lanugo, weighed 20% less than newborns without lanugo and were born early in the season to lowbody-mass females 4‐6 years of age. Among intermediate-age females (7‐10 years old), percentage of lanugo on pups was correlated negatively with female postpartum body mass but not with female age. Thus, maternal condition rather than age had stronger effects on stage of development of offspring at birth. Overall, maternal age explained 54% of the variance in birth mass, whereas postpartum mass of females explained only 20% of the variance. These relationships did not differ with sex of the pup, although male pups were 3.7% heavier than female pups. Effects of maternal age were strongest among young females; however, reproductive parity was more important than age itself in determining offspring birth mass.