Small-for-gestational-age births in the United States: an age-period-cohort analysis

BACKGROUND: During the last 2 decades, the rate of low birthweight has increased, as has the rate of preterm delivery, among both whites and blacks. Examination of causes for these secular trends has focused largely on changes in the distributions of maternal age and, less commonly, on birth cohort. Little is known as to how age, period, and birth cohort interact on trends in small births at term. METHODS: The U.S. natality files were used to assess trends in term (>/=37 weeks gestation) small-for-gestational age (SGA) births for 7 5-year maternal age groups (15-19 through 45-49 years), 6 delivery periods (1975, 1980, 1985, 1990, 1995, and 2000), and 12 5-year maternal birth cohorts (1926-1930 through 1981-1985). SGA births were defined as sex-specific birthweight below the 10th percentile for gestational age based on 1995 livebirths in the United States. Logistic regression models were fit to determine the independent effects of age, delivery period, and birth cohort on term SGA trends, separately for blacks and whites. RESULTS: Between 1975 and 2000, term SGA births declined by 23% (from 21% to 16%) among blacks and by 27% (from 12% to 9%) among whites. Term SGA births declined with increasing age up to 30-34 years, but increased among older women. Within strata of maternal age, the risk also declined with later maternal birth cohorts, among both blacks and whites. The strongest influence on SGA trends was from maternal age, followed by maternal birth cohort, and lastly by delivery period. In general, for any combination of age, period, and birth cohort, blacks showed 1.5- to 2-fold higher rates of term SGA than whites. CONCLUSIONS: The persistence of strong maternal age effects on risk of term SGA births suggests that the effect of age is at least partly the result of biologic factors. Term SGA trends were generally consistent for blacks and whites, although the magnitude of difference in the risks for combinations of age, period, or mother's birth cohort was higher among blacks than whites.     

Parental age difference and adverse perinatal outcomes in the United States

This study was undertaken to examine the relationship between paternal and maternal age differences and adverse perinatal outcomes in the United States. Data were obtained on singleton pregnancies delivering at >or=20 weeks gestation in the United States in 1995-97 from the National Center for Health Statistics data sets. Adverse perinatal outcomes that were evaluated included fetal death rate (>or=20 weeks), preterm delivery <37 weeks and small-for-gestational-age (SGA) births (birthweight <10th centile for gestational age and corrected for sex). Age difference was defined as paternal minus maternal age. The analysis included 8995274 pregnancies (11.3% blacks, 88.7% whites). An increase in fetal death rate, preterm delivery and SGA births was noted among white women who were older than their male partners. For black mothers older than their partners, there was an increase in fetal death rate when the women were <20 years old, but a decrease in fetal death rate when >35 years old. Neither rates of preterm delivery nor SGA births were increased much for black women with varying parental age differences. This demonstrates that race and maternal age both contribute to the effects of parental age difference on adverse perinatal outcomes.     

母亲出生体重与新生儿出生体重的关系研究

目的 探讨母亲出生体重与新生儿出生体重的关系,以便为研究母亲宫内发育不良对子代发育的影响提供线索。方法 通过巢式病例对照研究,采用多重线性回归分析了解母亲出生体重与新生儿出生体重的关系,并以非条件Logistic回归分析进一步探讨母亲出生体重对小于胎龄儿（small for gestational age,SGA）、大于胎龄儿（large for gestational age,LGA）的影响。结果 SGA的发生率为7.04%,LGA发生率为14.65%。多重线性回归分析结果显示,母亲出生体重与新生儿出生体重呈正相关,母亲出生体重每增加1 kg,新生儿出生体重增加174 g（β=0.174,95% CI:0.134~0.213）。随母亲出生体重的增加,SGA发生率递减（χ_趋势2=13.791,P<0.001）,LGA的发生率递增（χ_趋势2=7.900,P=0.005）,母亲低出生体重（<2 500 g）是SGA的危险因素（OR=2.458,95% CI:1.333~4.534）;以孕期增重分层分析后,结论一致,但出生体重较低的孕妇（＜2 500 g）孕期增重不足会导致SGA发生风险增高。结论 孕妇出生体重低是分娩SGA的危险因素,随着孕妇出生体重增加,新生儿出生体重增大,但未发现LGA与孕妇出生体重有关。     

Risk factors for low birthweight in the public-hospitals at Peshawar,NWFP-Pakistan

Background  

Low birthweight is a widely used indicator of newborn health. This study investigates the association of birthweight <2.5 kg (LBW) with a wide range of factors related to geo-demographics, maternal health and pregnancy history in public hospitals at Peshawar, North West Frontier Province (NWFP) Pakistan. It is noted that that Low birthweight may arise for two different reasons, one related to gestational age and the other corresponding to births that are small for gestational age (SGA).     

小于胎龄儿产科危险因素的病例对照研究

目的探讨产科因素及孕母文化程度与小于胎龄儿（SGA）之间的关系。方法采用病例对照方法，选取于2000年1月至2004年10月在第三医院出生的单胎活产SGA，全部病例共834例（男443例，女391例）作为病例组。以胎儿性别及出生胎龄进行频数匹配，按1：3的比例，采用完全随机抽样方法选取性别及胎龄别出生体重在10％～90％分位的适于胎龄儿2502名（男1329名，女1173名）为对照组，比较了病例组及对照组新生儿母亲年龄、文化程度及主要产科危险因素的比例。结果多因素logistic回归分析显示，SGA病例组母亲妊娠合并妊娠高血压综合征（妊高征）、羊水过少、有既往异常妊娠史和病毒性肝炎与对照组比较，OR值（95％Cj）分别为4．00（2．81～5．71）、2．95（2．27～3-83）、5．95（3．05～10．64）和0．50（0．30～0．84）；SGA母亲为初中及以下文化程度者与大专或以上文化程度者比较OR=3．46（95％CI：2．75～4．24）。其他因素与SGA无统计学意义的关联。结论孕母文化程度低、孕期合并妊高征、羊水过少、不良妊娠史可显著增加SGA发生的危险性。     

Risk factors for small-for-gestational age births among infants in Brazil

OBJECTIVE: To assess the risk factors for small-for-gestational-age (SGA) births. METHODS: All live births occurring in the city of Pelotas, Brazil, between October and December 1993 were identified and mothers interviewed soon after delivery. Birthweight was recorded by the maternity staff. Gestational age was obtained from the mothers' recall of their date of last menstrual period. SGA was defined as a birthweight below the 10th percentile for gestational age and sex, according to the reference developed by Williams. Chi-square test and logistic regression were used in the crude and multivariate analysis, respectively. RESULTS: In all, 1082 births were identified. The prevalence of SGA was 13.1%. Even after adjusting for possible confounding variables, the odds ratio for SGA among those infants whose family income was <1 minimum wage was 8.81 (95% CI, 1.12-69.46) times higher than among those for infants with a family income > or = minimum wage. An antenatal care of low quality was associated with an odds ratio of 3.28 (95% CI, 1.09-9.91) for SGA. Short maternal stature and maternal smoking during pregnancy were also associated with SGA births. CONCLUSIONS: Low socioeconomic status, maternal smoking during pregnancy, maternal height and an antenatal care of low quality are the main risk factors for SGA births.     

Intergenerational and environmental factors influencing pregnancy outcomes

PURPOSE: Factors that relate to the mother's own course of growth and development might influence later reproductive performances. This study examines the effect of maternal birth weight and maternal height and maternal weight gain, on term-small for gestational age (SGA) and preterm delivery.METHODS: Data used for this study were from the South Carolina Pregnancy Risk Assessment Monitoring System (PRAMS) and birth certificate files for 1993-1995. Since PRAMS data were weighted to adjust for sampling probabilities, non-response and survey design, Survey Data Analysis (SUDAAN) software was used in all analyses.RESULTS: Maternal birth weight was strongly associated with term SGA (OR = 3.65; 95% CI = 1.83-7.29), but not preterm delivery among black mothers; it was associated with preterm delivery (OR = 1.86; 95% CI = 1.09-3.17), but not term-SGA for white mothers. Maternal birth weight was associated with term SGA among nonsmokers only (OR = 2.34; 95% CI = 1.33-4.11). Maternal weight gain modified the effect of height on birth outcomes. Among women with inadequate weight gain, there was a 3-fold increase in risk for term-SGA (OR = 3.06; 95% CI = 2.41-3.89) for short maternal height, but not for preterm delivery. Among women with adequate plus weight gain, the association between short maternal height and term-SGA was 2.7 (95% CI = 0.55-9.43) compared to 3.67 (95% CI = 0.1.41-9.56) between short maternal height and preterm delivery. Maternal weight gain also modified the effect of maternal height on both outcomes for black mothers and for nonsmokers only.CONCLUSIONS: Findings indicate the need for interventions directed to those women who can benefit most from appropriate targeted weight gain recommendations. Therefore, prevention methods should be implemented to encourage short stature women to gain adequate weight during pregnancy.     

Uptake and safety of hepatitis A vaccination during pregnancy: A Vaccine Safety Datalink study

IntroductionInfection with hepatitis A virus (HAV) during pregnancy, although uncommon, is associated with gestational complications and pre-term labor. Hepatitis A vaccine (HepA) is recommended for anyone at increased risk for contracting hepatitis A, including women at risk who are also pregnant. Limited data are available on the safety of maternal HepA vaccination.ObjectivesAssess the frequency of maternal HepA receipt and evaluate the potential association between maternal vaccination and pre-specified maternal and infant safety outcomes.MethodsA retrospective cohort of pregnancies in the Vaccine Safety Datalink (VSD) resulting in live births from 2004 through 2015 was included. Pregnancies with HepA exposure were compared to those with other vaccine exposures, and to those with no vaccine exposures. Risk factors for contracting hepatitis A were identified up to one-year prior to or during the pregnancy using ICD-9 codes. Maternal and fetal adverse events were evaluated according to maternal HepA exposure status. Adjusted odds ratio (OR) were used to describe the association.ResultsAmong 666,233 pregnancies in the study period, HepA was administered at a rate of 1.7 per 1000 (n = 1140), most commonly within the first six weeks of pregnancy. Less than 3% of those exposed to HepA during pregnancy had an ICD-confirmed risk factor. There were no significant associations between HepA exposure during pregnancy and gestational hypertension, gestational diabetes, pre-eclampsia/eclampsia, cesarean delivery, pre-term delivery, and low birthweight. There was a statistically significant association between HepA exposure during pregnancy and small-for-gestational age (SGA) infants (aOR 1.32, [95% CI 1.09, 1.60], p = 0.004).ConclusionsThe rate of maternal HepA vaccination was low and rarely due to documented risk factors for vaccination. HepA vaccination during pregnancy was not associated with an increased risk for a range of adverse events examined among pregnancies resulting in live births, but an identified association between maternal HepA and SGA infant outcomes, while likely due to unmeasured confounding, warrants further exploration.     

The intergenerational relationship between mother's birthweight, infant birthweight and infant mortality in black and white mothers

Summary. The relationship between the birthweight of white and black mothers and the outcomes of their infants were examined using the 1988 National Maternal and Infant Health Survey. White and black women who were low birthweight themselves were at increased risk of delivering very low birthweight (VLBW), moderately low birthweight (MLBW), extremely preterm and small size for gestational age (SGA) infants. Adjustment for the confounding effects of prepregnant weight and height reduced the risks of all these outcomes slightly, and more substantially reduced the maternal birthweight associated risk of moderately low birthweight among white mothers. There was little effect of maternal birthweight on infant birthweight-specific infant mortality in white mothers; however, black mothers who weighed less than 4 lbs at birth were at significantly increased risk of delivering a normal birthweight infant who subsequently died. Although the risks for the various outcomes associated with low maternal birthweight were not consistently higher in black mothers compared with white mothers, adjustment for prepregnant weight and height had a greater effect in white mothers than in black mothers. We suggest that interventions to reduce the risks for adverse pregnancy outcomes associated with low maternal birthweight should attempt to optimise prepregnant weight and foster child health and growth.     

Risk factors in term children for visual impairment without a known prenatal or postnatal cause

Risk factors were studied for visual impairment in children without known pre- or postnatal cause, for a decrease of visual acuity. Children born at term 1979-98 and with a visual impairment were identified from the Swedish Register of Visually Impaired Children and data were linked with the Swedish Medical Birth Registry. Maternal characteristics such as maternal age, parity, maternal smoking habits in early pregnancy, maternal education, nationality, and subfertility were studied as well as maternal diagnoses such as pre-eclampsia, prolonged second stage of labour, abruptio placentae, and placenta praevia. Mode of delivery was analysed as well as birthweight, and birthweight in relation to gestational age. Abruptio placentae turned out to be the strongest risk factor (OR = 8.24 [95% CI 5.01, 13.51]). Smoking did not give a statistically significant increased risk. There is an increased risk with breech delivery (OR = 2.01 [95% CI 1.28, 3.17]). Pre-eclampsia was associated with an increased risk (OR = 2.22 [95% CI 1.46, 3.38]). There is also an increase in risk at low birthweight and small-for-gestational-age as well as birthweight > 4 kg and large-for-gestational-age. In this study we found that risk factors particularly worth noticing in term children with a presumed perinatal cause of visual impairment are abruptio placentae, pre-eclampsia, excessively low as well as excessively high birthweight, and breech delivery, a fact worth noticing in current discussion on risks, advantages or excessive exploitation of caesarean section.     

Maternal night blindness during pregnancy is associated with low birthweight, morbidity, and poor growth in South India

Maternal night blindness is common during pregnancy in many developing countries. Previous studies have demonstrated important consequences of maternal night blindness during pregnancy on the health of the mother and newborn infant. We compared birthweight, 6-mo infant mortality, morbidity, and growth among infants of women who did and did not report a history of night blindness from a community-based, randomized trial of newborn vitamin A supplementation in south India. Birthweight was measured within 72 h of delivery. Infants were followed until 6 mo of age for mortality and morbidity was assessed at household visits every 2 wk. Anthropometry was assessed at 6 mo of age. A total of 12,829 live-born infants were included, 680 of whom were infants of mothers with night blindness during the index pregnancy. Maternal night blindness was associated with an increased risk of low birthweight in a dose-dependent fashion based on birthweight cut-offs: <2500 g, adjusted relative risk (RR) = 1.13 (95% CI = 1.01, 1.26); <2000 g, adjusted RR = 1.70 (95% CI = 1.27, 2.26); <1500 g, adjusted RR = 3.38 (95% CI = 1.18, 6.33); with an increased risk of diarrhea (adjusted RR = 1.16, 95% CI = 1.03, 1.30), dysentery (adjusted RR = 1.25, 95% CI = 1.03, 1.53), acute respiratory illness (adjusted RR = 1.32, 95% CI = 1.21, 1.44), and poor growth at 6 mo; underweight (adjusted RR = 1.14, 95% CI = 1.02, 1.26), stunting (adjusted RR = 1.19, 95% CI = 1.05, 1.34). Maternal night blindness was not associated with 6-mo infant mortality or wasting at 6 mo. This study demonstrates that there are important consequences to the infant of maternal vitamin A deficiency during pregnancy.     

Effect of multiple micronutrient supplementation on pregnancy and infant outcomes: a systematic review

Supplementation with multiple micronutrients (MM) during pregnancy may result in improved pregnancy and infant outcomes. We conducted meta-analyses of randomised controlled trials that evaluated the effects of prenatal supplementation with MM (defined as containing at least five micronutrients and typically included iron or iron and folic acid). The outcomes of interest were low birthweight (<2500 g), birthweight, small-for-gestational age (SGA), gestational age, preterm birth (<37 weeks' gestation), stillbirth and neonatal death, maternal morbidity and mortality. We identified eligible studies through PubMed and EMBASE database searches. Meta-analyses were performed by pooling results for outcomes that were reported from more than one trial and sub-analyses were conducted to evaluate the effect of timing of intervention and amount of iron. We included published results from 16 trials in this review. Compared with control supplementation that was usually iron plus folic acid in most studies, MM supplementation resulted in a significant reduction in the incidence of low birthweight [pooled risk ratio (RR) 0.86; 95% confidence interval (CI) 0.81, 0.91] and SGA (pooled RR 0.83 [95% CI 0.73, 0.95]) and an increase in mean birthweight (weighted mean difference (WMD) 52.6 g [95% CI 43.2 g, 62.0 g]). There was no significant difference in the overall risk of preterm birth, stillbirth, and maternal or neonatal mortality, but we found an increased risk of neonatal death for the MM group compared with iron-folate in the subgroup of five trials that began the intervention after the first trimester (RR 1.38 [95% CI 1.05, 1.81]). None of the studies evaluated maternal morbidity. Compared with iron plus folic acid supplementation alone, prenatal maternal supplementation with MM resulted in a reduction in the incidence of low birthweight and SGA but increased risk of neonatal death in the subgroup of studies that began the intervention after the first trimester.     

Weight loss during pregnancy is associated with adverse pregnancy outcomes among HIV-1 infected women

In a prospective study of 1002 pregnant, HIV-1 infected Tanzanian women, we examined the incidence of fetal death, preterm delivery, low birth weight (LBW), and small for gestational age (SGA) births in relation to maternal anthropometry at the first prenatal visit, weight loss, and low weight gain during pregnancy. Anthropometric measurements were obtained monthly during the 2nd and 3rd trimesters. Low maternal height and weight at the first visit were significantly related to lower mean birth weight and increased risk of SGA, but not to preterm delivery. Maternal stature < 150 cm was significantly related to fetal death. Weight loss during pregnancy, defined as a negative slope of the regression of weight measurements on the week of gestation, occurred in 10% of the women. It was related to increased relative risk (RR) of fetal death (RR = 1.83, 95% CI = 0.93, 3.57), preterm delivery (RR = 1.85, 95% CI = 1.40, 2.44), and LBW (RR = 2.85, 95% CI = 1.69, 4.79) after adjusting for multivitamin supplementation, height, primiparity, baseline weight, malaria, CD4 cell count, HIV disease stage, and intestinal parasitoses. The significant association with fetal death was stronger for weight loss during the 2nd trimester, whereas increased risks of preterm delivery and LBW were higher for weight loss during the 3rd. Similar but weaker associations were found with low weight gain during pregnancy (slope < 25th percentile). We conclude that poor anthropometric status at the first prenatal visit and weight loss during pregnancy among HIV-1 infected women are strong risk factors for adverse pregnancy outcomes.     

Factors affecting birth weight in Kuwait. Part I, Maternal, dietary and socioeconomic factors.

The aim of this study was to determine the effect of maternal nutrition, vitamin supplementation and socioeconomic status on infants birth weight in Kuwait. The weight of 1995 newborn Kuwaiti infants was recorded shortly after delivery. Data on mothers' bodyweight just before pregnancy, height, weight gain during pregnancy and vitamin intake were recorded. Mothers were interviewed to collect data in family income, educational level and employment during pregnancy. The results show that mean birth weight in Kuwait (3.50 Kg) compares favourably with any country. The birth weight was affected by several factors. Maternal body weight, height and weight gain during pregnancy were positively correlated with birth weight. The results also show that the intake of vitamin supplement during pregnancy did not have a significant inference on birth weight. Obese mothers consuming a reducing diet delivered babies with birth weight slightly above normal. The results show that mothers from high income families had heavier babies when compared with a low income group. On the other hand, educated and employed mothers were more liable to have slightly smaller babies when compared with illiterate or unemployed mothers.     

Can we explain why Brazilian babies are becoming lighter?

BACKGROUND: We tried to explain why a marked decrease in birthweight of 122 g occurred over a 15-year period in Ribeir?o Preto, Brazil. METHODS: Factors reflecting biological, social, and health care characteristics (infant gender, parity, maternal age, marital status, type of hospital, maternal smoking, preterm birth, small for gestational age [SGA], and prenatal care) were assessed on 6711 newborns in 1978/1979 and 2838 in 1994 using multiple linear regressions. RESULTS: The birthweight distribution shifted to the left and the residual distribution of small preterm babies increased from 1.9% to 3.4%. Only marital status and preterm delivery would have decreased the difference in birthweight over time, explaining for each of them around 30 g of the 122 g. Increasing levels of attendance at antenatal care over time might have decreased the birthweight difference by 40 g. Maternal age and SGA explained little of the decreasing trend. Reductions in maternal smoking would have increased mean birthweight slightly. In stratified analysis the downward trend was more marked among mothers with high education (-202 g) and those delivered by caesarean section (-194 g). After adjusting for all those significant variables mean birthweight was still 74 g (95% CI: -97, -50 g) lower in 1994 than in 1978/1979. CONCLUSION: The trend could be explained in part by factors related to marital status that might reflect dysfunctional families in the Brazilian context and the preterm increase that might be associated with advances in medical technology. The high attendance at antenatal clinics or factors associated with it might have prevented a further decrease in birthweight. Our results may be compatible with the high economic development of Ribeir?o Preto within Brazil, together with factors associated with its unfavourable lifestyle.     

5 012名单胎活产儿小于胎龄儿和大于胎龄儿发生率及其影响因素研究

目的 了解湖南省两市小于胎龄儿(SGA)和大于胎龄儿(LGA)的发生率,并分析其影响因素,为预防SGA和LGA的发生提供理论依据。方法 采用分层整群抽样方法,选择2016年1-6月在湖南省株洲市和湘潭市当地助产机构住院分娩的孕妇作为研究对象,收集孕妇及其丈夫的社会人口学特征、家庭经济情况和妊娠情况,记录新生儿出生结局。运用χ²检验和Fisher确切概率法进行单因素的SGA和LGA发生率比较,采用无序多分类Logistic回归模型进行多因素SGA和LGA的影响因素分析。结果 SGA发生率为6.5%(328/5 012),LGA发生率为7.9%(394/5 012)。无序多分类Logistic回归模型显示,孕妇孕期进行规范产前检查为SGA和LGA共同的保护因素,孕期贫血和妊娠期高血压疾病是SGA的危险因素,妊娠糖尿病、孕妇年龄≥35岁、丈夫年龄≥30岁是LGA的危险因素。结论 孕妇孕期进行规范产前检查可降低SGA和LGA的发生风险,孕期贫血和妊娠期高血压疾病会增加SGA的发生风险,妊娠糖尿病、孕妇高龄和丈夫高龄会增加LGA的发生风险。     

Determinants of developmental delay in infants aged 12 months

The aim of this study was to determine which demographic, maternal, obstetric and postnatal variables were associated with achievement of developmental milestones at the age of 12 months in term infants. Mothers and babies were enrolled in the Auckland Birthweight Collaborative Study shortly after birth. All infants were full term (gestation >or= 37 weeks). Approximately half of the sample were small for gestational age (SGA = birthweight 10th percentile). A maternal interview was conducted soon after birth. Phase 2 of the study occurred 12 months later when mothers were sent a postal questionnaire requesting information about the child's health and development during the first year of life using the Denver Prescreening Developmental Questionnaire. Seven hundred and forty-four (85.4%) European mothers returned the postal questionnaire. SGA children were not at increased risk of developmental delay at 12 months of age. In a sample representative of New Zealand European children, after adjustment for the effects of potential confounders, maternal smoking during pregnancy (OR = 2.1 [95% CI 1.1, 4.0]), maternal smoking during the first year of life (OR = 1.9 [95% CI 1.0, 3.8]) and low levels of satisfaction with parenting (OR = 2.4 [95% CI 1.1, 5.2]) were associated with significantly increased risk of developmental delay. In the subgroup of SGA children, maternal smoking during pregnancy (OR = 2.9 [95% CI 1.4, 6.2]), high levels of stress associated with parenting (OR = 2.2 [95% CI 1.2, 4.0]), and low levels of satisfaction with parenting (OR = 4.3 [95% CI 1.3, 13.5]) were significantly associated with developmental delay after adjustment for the effects of potential confounders. In conclusion, maternal and postnatal factors were better predictors of developmental delay than demographic variables.     

Modulation off birthweight through gestational age and fetal growth

Summary Several factors are known to affect birthweight and their effects are variously mediated through gestational duration or through fetal growth conditional on this gestation, in order to quantify independent associations of birthweight conditional and unconditional on gestational age, all 2538 mothers of singleton babies delivered during 1993 in two Maternity Hospitals in Athens were interviewed and their obstetric records abstracted. Birthweight was modelled as outcome variable through multiple regression including 32 potentially predictive factors. The regression model was fitted with and without gestational age as an additional independent variable in order to apportion birthweight associations into those independent of, or mediated through, gestational length. The factors studied were found to be classifiable into the following categories: factors associated with birthweight mostly through increases in gestational duration, either positively (age at menarche, long menstrual cycles, parity 4 or higher), or negatively (single motherhood, maternal age, tobacco smoking); those associated with birthweight mostly through increase of birthweight conditional on gestational duration, either positively (male gender, short menstrual cycles, maternal pre-pregnancy weight, anaemia, oedema) or inversely (employment during pregnancy, stillbirth, primiparity, pregnancy induced hypertension, coffee drinking); and those associated with birthweight through apparently dual effects, either positively (maternal education) or inversely (perceived stress, bleeding during pregnancy). The other studied factors were not demonstrably related to birthweight in this data set. Identification and quantification of these relations is useful for understanding underlying physiological and pathophysiological processes and for increasing specificity in exploring the association of birthweight with adult onset diseases, like coronary heart disease or cancer.     

Determinants of Small for Gestational Age Birth at Term

Background: Being born small for gestational age (SGA) is an indicator of intrauterine growth restriction (IUGR) and later health risks. This study investigated determinants of severe and moderate SGA (respectively, birthweight <3rd percentile and 3rd to <10th percentile for gestational age and sex). Methods: A total of 2195 term pregnancies from a prospective cohort were studied. Prenatal data arose from maternal interview at 10–22 weeks of gestation and perinatal data were collected from hospital charts. Severe and moderate SGA were classified by Canadian population standards. Risk factors for SGA were identified from fitting multivariable logistic regression models. Results: Multivariable associations with severe SGA were: maternal age ≥ 35 [odds ratio (OR) 3.2 [95% confidence interval (CI) 1.4, 6.9]], maternal smoking during pregnancy (OR 5.3 [95% CI 2.4, 11.7]), preeclampsia (OR 4.6 [95% CI 1.6, 13.2]) and threatened preterm labour (OR 3.9 [95% CI 1.3, 11.4]). Primiparity was associated with both severe and moderate SGA with OR 2.4 [95% CI 1.1, 5.1] and OR 1.9 [95% CI 1.3, 2.9] respectively. Underweight pre‐pregnancy body mass index was associated with moderate SGA (OR 2.4 [95% CI 1.2, 5.0]). Inclusion of placental weight, in the final model attenuated the associations. Conclusions: This study demonstrated different determinants for severe and moderate SGA. We speculate that the majority of severe SGA infants are IUGR while moderate SGA infants may be a mixture of IUGR and constitutionally small newborns. This study has also contributed evidence linking preterm labour and SGA as two, potentially related, outcomes of overlapping causal mechanisms reflective of ischaemic placental disease.     

Maternal Dietary Selenium Intake during Pregnancy Is Associated with Higher Birth Weight and Lower Risk of Small for Gestational Age Births in the Norwegian Mother,Father and Child Cohort Study

Selenium is an essential trace element involved in the body’s redox reactions. Low selenium intake during pregnancy has been associated with low birth weight and an increased risk of children being born small for gestational age (SGA). Based on data from the Norwegian Mother, Father and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN), we studied the association of maternal selenium intake from diet and supplements during the first half of pregnancy (n = 71,728 women) and selenium status in mid-pregnancy (n = 2628 women) with birth weight and SGA status, according to population-based, ultrasound-based and customized growth standards. An increase of one standard deviation of maternal dietary selenium intake was associated with increased birth weight z-scores (ß = 0.027, 95% CI: 0.007, 0.041) and lower SGA risk (OR = 0.91, 95% CI 0.86, 0.97) after adjusting for confounders. Maternal organic and inorganic selenium intake from supplements as well as whole blood selenium concentration were not associated with birth weight or SGA. Our results suggest that a maternal diet rich in selenium during pregnancy may be beneficial for foetal growth. However, the effect estimates were small and further studies are needed to elucidate the potential impact of selenium on foetal growth.