Fields David A, Krishnan Sowmya, Wisniewski Amy B
Department of Pediatrics Section of Endocrinology and Diabetes, Children's Medical Research Institute's Diabetes & Metabolic Research Program, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, USA.
Gend Med. 2009 Jul;6(2):369-75. doi: 10.1016/j.genm.2009.07.003.
Early development of the percentage of fat and muscle is rarely considered, but is important because excessive fat is related to the development of diabetes and other morbidities later in life. In pediatric medicine, there are few to no data comparing sex differences in body composition in the first months of life despite the fact that males are typically longer and weigh more than girls at birth.
The purpose of this study was to determine whether observed sex differences in body composition at birth persist through the first 6 months of life.
Participants were healthy, full-term, male and female newborns. Children throughout the Oklahoma City, Oklahoma, metropolitan area were enrolled. The inclusion criteria were: mothers aged 18 to 45 years at the time of delivery; a term pregnancy lasting >or=37 weeks of gestation (determined by mother's physician); weight adequate for gestational age; and a hospital stay for the infant of <3 days following delivery. The exclusion criteria were: maternal tobacco use or alcohol consumption (>1 drink per week) during pregnancy; gestational diabetes; preeclampsia; and infants with presumed or known congenital birth defects. Baseline assessment at birth included length and weight. Newborns had their body composition (percent fat [%fat], total fat, and fat-free mass) determined at approximately 1 month of age using whole body plethysmography. Mothers were invited to have their children take part in a 5-month extension that conducted additional body composition measurements at 3 and 6 months of age.
Sixty-four girls (mean [SD] age at time of testing, 20.9 [7.9] days; birth weight, 3500 [388] g; birth length, 49.9 [2.4] cm; white race, 73.4%) and 53 boys (mean age at time of testing, 20.2 [7.3] days; birth weight, 3353 [413] g; birth length, 51.0 [2.4] cm; white race, 69.8%) were assessed and included in the study. At birth, girls were significantly shorter and weighed more than boys (both, P < 0.05). At ~1 month of age, body composition revealed that girls had significantly greater %fat (15.1% vs 12.7%; P < 0.05) and less fat-free mass (3182 [303] vs 3454 [361] g; P < 0.001) than did boys. At 3 months of age, girls continued to have significantly less fat-free mass (4379 [347] vs 4787 [310] g; P < 0.01) than did boys; however, by 6 months of age, no significant sex difference was observed in any body composition variable studied.
In this small sample of healthy, full-term newborns, at ~1 month of age, statistically significant differences in %fat and fat-free mass existed between girls and boys; however, by 6 months of age, these differences no longer existed.
脂肪和肌肉比例的早期发育很少被考虑，但这很重要，因为过多脂肪与日后生活中糖尿病及其他疾病的发生有关。在儿科学中，尽管男性出生时通常比女孩更长、更重，但关于出生后最初几个月身体成分性别差异的比较数据很少甚至没有。
本研究的目的是确定出生时观察到的身体成分性别差异在出生后的前6个月是否持续存在。
参与者为健康的足月男、女新生儿。招募了俄克拉荷马城大都市地区的儿童。纳入标准为：分娩时母亲年龄在18至45岁之间；足月妊娠持续≥37周（由母亲的医生确定）；体重符合孕周；婴儿出生后住院时间<3天。排除标准为：母亲在孕期吸烟或饮酒（每周>1杯）；妊娠期糖尿病；先兆子痫；以及有假定或已知先天性出生缺陷的婴儿。出生时的基线评估包括身长和体重。新生儿在大约1月龄时使用全身体积描记法测定其身体成分（脂肪百分比[%fat]、总脂肪和去脂体重）。邀请母亲让其孩子参加为期5个月的随访，在3个月和6个月时进行额外的身体成分测量。
评估并纳入研究的有64名女孩（测试时平均[标准差]年龄为20.9[7.9]天；出生体重3500[388]g；出生身长49.9[2.4]cm；白人种族占73.4%）和53名男孩（测试时平均年龄为20.2[7.3]天；出生体重3353[413]g；出生身长51.0[2.4]cm；白人种族占69.8%）。出生时，女孩比男孩明显更矮但更重（均P<0.05）。在约1月龄时，身体成分显示女孩的%fat显著更高（15.1%对12.7%；P<0.05），而去脂体重比男孩更少（3182[303]对3454[361]g；P<0.001）。在3月龄时，女孩的去脂体重仍显著低于男孩（4379[347]对4787[310]g；P<0.01）；然而，到6月龄时，在所研究的任何身体成分变量中均未观察到显著的性别差异。
在这个健康足月新生儿的小样本中，在约1月龄时，女孩和男孩在%fat和去脂体重方面存在统计学上的显著差异；然而，到6月龄时，这些差异不再存在。
