The effect of multiple pregnancies on lumbar bone mineral density in Japanese women

The influence of lactation and its duration on bone mineral density in pregnancy and postpartum: A systematic review with meta-analysis

BACKGROUND

There is a plethora of research on the association of parity and duration of lactation with bone mineral density (BMD) during and after pregnancy. However, there are no consensus conclusions on the impact of the duration of lactation on BMD.

AIMS

The aim of this study was to examine the effect of pregnancy, and the duration of lactation on BMD during pregnancy, postpartum phase and 12 months post-delivery.

METHODS

The search terms 'parity' 'lactation' 'BMD' were searched for using PubMed, CINAHL, SCOPUS and EMBASE databases in English language. Two independent reviewers assessed the quality of the included studies using Critical Appraisal Skills Program (CASP) appraisal tool and extracted data on BMD (g/cm²) in Excel. A meta-analysis was conducted with a random effect model using Cochrane Review Manager (Rev 5.4) to analyse the outcome. Heterogeneity was assessed with Chi Squared and I² test. The duration of lactation was grouped into short lactation duration (SLD), ≤4 months and longer lactation duration (LLD) > 6 months.

RESULTS

Twenty-one studies were included in this review with four studies included in the meta-analysis. BMD reduced during pregnancy and lactation. Recovery and net gains in BMD followed weaning. However, at 12 months postpartum, women in the LLD group had significant losses at the lumbar spine while those in the SLD recovered BMD. Between the SLD and LLD groups, the change in BMD was not significant 0.48 g/cm² (95% CI -0.14, 1.10, p = 0.13). BMD losses were greater in primiparous women than multiparous women.

CONCLUSION

Women who breastfed for >6 months had significantly reduced BMD. However, compared to women that breastfed for a ≤4 months there was no significant change in BMD. Further investigation is needed to clarify the association between lactation and BMD in a postpartum population in those women extending breastfeeding beyond one year.

Quantitative ultrasound assessment of the effect of parity on bone mineral density in females

Background

The effect of pregnancy and breastfeeding on a female’s bone mineral density (BMD) is controversial. This prospective study aims to investigate the effect of parity on BMD among pre-menopausal multiparous females using quantitative ultrasound as a screening method and females with no pregnancies (nulliparous) as a control group.

Methods

A portable ultrasound-based bone densitometer (DMS PEGASUS SMART, Mauguio, France) was used to indirectly assess the BMD in 51 multiparous (29–45 years) and 51 nulliparous Arabic females (18–35 years) by quantifying the broadband ultrasound attenuation (BUA) from their right calcaneus bone. BUA > 70 db/mhz = normal, BUA 65–69.9 db/mhz = below average, BUA 55–64.9 db/mhz = osteopenia and BUA < 55 db/mhz = osteoporosis.

Results

There was a significant difference in mean BUA between multiparous and nulliparous females (74.1 db/mhz vs. 69.3 db/mhz, p = 0.006). The prevalence of normal BMD was significantly higher in the nulliparous group than in the multiparous group (70.6% vs. 47.1%, p = 0.02). Osteoporosis was found in the multiparous group only (3/51). Among the multiparous females who breastfed (43/51), a total of 51.2% (22/43) had normal BMD, 25.6% (11/43) had BMD below average, 18.6% (8/43) had osteopenia and 4.7% (2/43) had osteoporosis. No significant differences in mean BUA (p = 0.2) were found between the group of females who breastfed for one year (13/43; BUA: 70.5 ± 9.4), the group of females who breastfed for 6–11 months (8/43; BUA: 70.6 ± 10.0) and those who breastfed for less than six months (22/43; BUA: 71.6 ± 9.4). A binary logistic regression model built for predicting BMD normality showed significance for the variable parity (p = 0.03), while the effect of the possible confounding variables BMI and age on BMD normality was found to be non- significant (p = 0.1 and p = 0.6, respectively).

Conclusion

Parity affects the BMD, as assessed by a portable ultrasound-based bone densitometer, of young and middle-aged females as compared to the BMD of nulliparous females.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12905-021-01516-w.

Effect of parity on bone mineral density: A systematic review and meta-analysis

INTRODUCTION

Parity has been suggested as a possible factor affecting bone health in women. However, study results on its association with bone mineral density are conflicting.

METHODS

PubMed, EMBASE, the Cochrane Library, and Korean online databases were searched using the terms "parity" and "bone mineral density", in May 2016. Two independent reviewers extracted the mean and standard deviation of bone mineral density measurements of the femoral neck, spine, and total hip in nulliparous and parous healthy women.

RESULTS

Among the initial 10,146 studies, 10 articles comprising 24,771 women met the inclusion criteria. The overall effect of parity on bone mineral density was positive (mean difference=5.97mg/cm²; 95% CI 2.37 to 9.57; P=0.001). The effect appears site-specific as parity was not significantly associated with the bone mineral density of the femoral neck (P=0.09) and lumbar spine (P=0.17), but parous women had significantly higher bone mineral density of the total hip compared to nulliparous women (mean difference=5.98mg/cm²; 95% CI 1.72 to 10.24; P=0.006). No obvious heterogeneity existed among the included studies (femoral neck I²=0%; spine I²=31%; total hip I²=0%).

CONCLUSION

Parity has a positive effect on bone in healthy, community-dwelling women and its effect appears site-specific.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

During pregnancy and lactation, female physiology adapts to meet the added nutritional demands of fetuses and neonates. An average full-term fetus contains ∼30 g calcium, 20 g phosphorus, and 0.8 g magnesium. About 80% of mineral is accreted during the third trimester; calcium transfers at 300-350 mg/day during the final 6 wk. The neonate requires 200 mg calcium daily from milk during the first 6 mo, and 120 mg calcium from milk during the second 6 mo (additional calcium comes from solid foods). Calcium transfers can be more than double and triple these values, respectively, in women who nurse twins and triplets. About 25% of dietary calcium is normally absorbed in healthy adults. Average maternal calcium intakes in American and Canadian women are insufficient to meet the fetal and neonatal calcium requirements if normal efficiency of intestinal calcium absorption is relied upon. However, several adaptations are invoked to meet the fetal and neonatal demands for mineral without requiring increased intakes by the mother. During pregnancy the efficiency of intestinal calcium absorption doubles, whereas during lactation the maternal skeleton is resorbed to provide calcium for milk. This review addresses our current knowledge regarding maternal adaptations in mineral and skeletal homeostasis that occur during pregnancy, lactation, and post-weaning recovery. Also considered are the impacts that these adaptations have on biochemical and hormonal parameters of mineral homeostasis, the consequences for long-term skeletal health, and the presentation and management of disorders of mineral and bone metabolism.

Increased bone mineral density is associated with breastfeeding history in premenopausal Spanish women

INTRODUCTION

During lactation abundant calcium is lost from the mother as a result of the amount of breast milk produced. Lactation leads to transient fragility, with some women experiencing even fragility fractures, but nearly all of these women subsequently undergo a large increase in bone mineral density (BMD), confirming that the BMD must have declined during lactation but it increases after weaning. We have retrospectively examined the relationship between the duration of breastfeeding and bone properties in Spanish premenopausal healthy women, to identify the site-specific changes in BMD.

MATERIAL AND METHODS

Four hundred and thirty-three premenopausal healthy women, 295 with a mean of 7.82 ±6.68 months of exclusive breastfeeding and 138 control women, were studied. We examined total, trabecular and cortical volumetric BMD (mg/mm(3)) at the distal radius using peripheral quantitative computed tomography. Areal BMD (g/cm(2)) was measured using dual energy X-ray absorptiometry at the femoral neck, lumbar spine, trochanter and Ward's triangle. Phalangeal bone ultrasound was measured by amplitude-dependent speed of sound.

RESULTS

Areal BMD analysis at L2-L4 revealed significant intergroup differences (p < 0.05). There were significant intergroup differences in the volumetric BMD in both total and cortical bone (p < 0.05). The observed BMD of breast-feeders was higher than the BMD in non-breast-feeding women. Additionally, the lactation subgroup analysis revealed significant differences in the areal BMD at trochanter and L2-L4 (p < 0.05) and in the cortical volumetric BMD (p < 0.05).

CONCLUSIONS

This study adds to the growing evidence that breastfeeding has no deleterious effects and may confer an additional advantage for BMD in premenopausal women.

Adolescent fathers: knowledge of and involvement in the breast feeding process in Brazil

OBJECTIVE

to understand the ways in which adolescent fathers participate in the breast feeding process in the family environment in North-eastern Brazil.

METHODS

a descriptive, exploratory, qualitative study was undertaken involving 10 couples with infants aged 6-8 months living in a single community in Recife, Pernambuco, Brazil. Data were collected using semi-structured interviews with questions to guide the interviewer. Data were analysed using thematic content analysis, and interpreted under the theoretical reference of being an adolescent father within the context of breast feeding.

FINDINGS

from the data collected, three themes were identified: knowledge of the benefits of breast feeding for the child's health; discontinued participation of the father in breast feeding during the pregnancy-childbearing cycle; and exclusion of the adolescent father from the breast feeding process. The adolescent fathers knew about the benefits of breast feeding in terms of the child's health, but did not mention benefits for the mother, the family or society. For some adolescent fathers, their participation in the breast feeding process started during pregnancy, whereas for others, it was only initiated after the infant was born. One of the fathers was prevented, by his wife and mother-in-law, from participating in the breast feeding process.

CONCLUSIONS

the involvement of adolescent fathers in the breast feeding process oscillated during the pregnancy-childbearing cycle. This may be due to the patriarchal cultural heritage, Brazilian paternity laws, and the fact that these fathers were adolescents. This study showed that adolescent parents were knowledgeable about breast feeding. Finally, fathers want a new model of parenting in which the man participates in child care.

Role of calcium during pregnancy: maternal and fetal needs

Although the demand for additional calcium during pregnancy is recognized, the dietary reference intake for calcium was lowered for pregnant women in 1997 to amounts recommended for nonpregnant women (1,000 mg/day), and recently (November 2010) the Institute of Medicine report upheld the 1997 recommendation. It has been frequently reported that women of childbearing age do not consume the dietary reference intake for calcium and that calcium intake in the United States varies among ethnic groups. Women who chronically consume suboptimal amounts of calcium (<500 mg/day) may be at risk for increased bone loss during pregnancy. Women who begin pregnancy with adequate intake may not need additional calcium, but women with suboptimal intakes (<500 mg) may need additional amounts to meet both maternal and fetal bone requirements. The objective of this review is to elucidate the changes in calcium metabolism that occur during pregnancy as well as the effect of maternal calcium intake on both maternal and fetal outcomes.

Bone mineral density measurement in puerperal women as a predictor of persistent osteopenia

The clinical value of bone mineral density (BMD) measurement in puerperal women is uncertain. Our aim was to examine the effectiveness of BMD measurement in puerperal women for identification of persistent osteopenia and osteoporosis. We addressed cross-sectional and longitudinal changes in BMD, assessed using dual-energy X-ray absorptiometry (DXA), in a postpartum female cohort from a single center in Japan. We measured BMD of the lumbar spine (L2-L4) with DXA in 2,436 puerperal women within 7 days of delivery (study 1). For 210 of the women, the BMD was measured again after 5-10 years (study 2). In study 1, 8 (0.3%) of the women were osteoporotic, 37 (17.0%) were osteopenic, and 2,013 (82.6%) were normal. In study 2, 27 (71.1%) of the 38 osteoporotic or osteopenic women identified in the puerperal scan were still osteopenic at the scan after 5-10 years. Over the same period, only 7 (4.1%) of 172 initially normal women became osteopenic. The mean of the BMD change per year was 0.15 +/- 0.82%/year. Osteopenia was associated with a significantly lower body weight and body mass index at puerperium and after 5-10 years compared to normal women. The multiple regression analysis showed that BMD at the first scan negatively contributed and body weight changes between the scans positively significantly contributed to the BMD changes per year. Puerperal BMD remained static over the subsequent 5-10 years. If the women have a low BMD at this stage of their reproductive life, it tends not to improve over this time. Perhaps identification of this at-risk group may lead to effective interventions to reduce fracture risk in later life.

Influence of parity on bone mineral density and peripheral fracture risk in Moroccan postmenopausal women

The aims of the study were to determine: (1) the relationship between parity and bone mineral density (BMD); (2) the relationship between parity and osteoporotic peripheral fractures.

MATERIAL AND METHODS

The group studied included 730 postmenopausal women. Patients were separated into four groups according to the number of fullterm pregnancies, group 1: nulliparae, group 2: one to three pregnancies, group 3: four to five pregnancies, and group 4: six and more pregnancies. Additionally, patients were separated into three groups according to their ages, as <50 years, 50-59 years and >or=60 years.

RESULTS

The median parity was 4 [0-20]. All the patients with parity greater than six had spine and hip BMD values significantly lower than values in the other groups (p<0.001). After adjustment for age and body mass index (BMI), decreased lumbar and total hip BMD were still associated to increased parity (analysis of covariance (ANCOVA), p=0.04 and 0.023, respectively). The relation between parity and lumbar BMD was highly significant among women aged <50 years (age-adjusted p=0.022), while there was no parity-spine BMD association in the other age groups. The relation between parity and hip BMD was seen only in the group 50-59 years (age-adjusted p=0.042). A positive history for peripheral fractures was present in 170 (23%) patients. There was relationship between parity and peripheral fractures neither in the whole population nor in the sub-groups according to age.

DISCUSSION

The present study suggests that the BMD of the spine and hip decreases with an increasing number of pregnancies, and this situation shows variations in different age groups. However, there was no correlation between parity level and peripheral fractures.

Reproductive Factors Affecting the Bone Mineral Density in Postmenopausal Women

Osteoporosis has been defined as a metabolic bone disease characterized by a loss of bone mineral density (BMD) greater than 2.5 standard deviations below young adult peak bone mass or the presence of fracture. By considering that some factors related to female reproductive system might influence the ultimate risk of osteoporosis, we aimed to investigate if a relationship exists between the present BMD of postmenopausal women with their past and present reproductive characteristics. The present study focused on how BMD could be affected by the following factors in postmenopausal women, such as age at menarche, age at first pregnancy, the number of pregnancies and total breast-feeding time. We reviewed detailed demographic history of 303 postmenopausal women. According to the results of the present study, a negative correlation was found between the number of parities and BMD. The BMD values decreased as the number of pregnancies increased. When the BMD values for lumbar vertebrae 2 and Ward's triangle were investigated, it was observed that a significant difference exists between the women with no child birth and those with more than five parities. There was a significant relationship between age at first pregnancy and BMD values at the lumbar vertebrae 2 and Ward's triangle. Women who had five or more abortions were found to have significantly lower spine BMD values compared to women who had no abortions or women who had one or two abortions. These findings indicate that the increased risk of osteoporosis is associated with the increased number of pregnancies and abortions and higher age at first pregnancy.

Lactation and maternal bone health

Women lose bone during lactation, and this is an important mechanism to provide calcium for human milk. Bone loss during lactation occurs even in women with high calcium intakes. Lactation-induced bone loss is transient because bone density increases rapidly after weaning. Bone loss during lactation and recovery after weaning are related to ovarian function and the length of postpartum amenorrhea. The recovery of bone after weaning can occur with shortly spaced pregnancies. Women who have breastfed several infants do not have reduced bone density after menopause. Overall, the transient bone loss during lactation does not seem to increase a woman's risk of osteoporotic fracture in her elder years. Further research is needed on special subgroups of women, such as adolescents, women who are vitamin D deficient or have extremely low calcium intakes, and women who have simultaneously breastfed multiple infants to determine whether these women are able to regain sufficient bone mass after lactation to preserve their bone health.