Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester

Reported last menstrual period (LMP) is commonly used to estimate gestational age (GA) but may be unreliable. Ultrasound in the first trimester is generally considered a highly accurate method of pregnancy dating. The authors compared first trimester report of LMP and first trimester ultrasound for estimating GA at birth and examined whether disagreement between estimates varied by maternal and infant characteristics. Analyses included 1867 singleton livebirths to women enrolled in a prospective pregnancy cohort. The authors computed the difference between LMP and ultrasound GA estimates (GA difference) and examined the proportion of births within categories of GA difference stratified by maternal and infant characteristics. The proportion of births classified as preterm, term and post‐term by pregnancy dating methods was also examined. LMP‐based estimates were 0.8 days (standard deviation = 8.0, median = 0) longer on average than ultrasound estimates. LMP classified more births as post‐term than ultrasound (4.0% vs. 0.7%). GA difference was greater among young women, non‐Hispanic Black and Hispanic women, women of non‐optimal body weight and mothers of low‐birthweight infants. Results indicate first trimester report of LMP reasonably approximates gestational age obtained from first trimester ultrasound, but the degree of discrepancy between estimates varies by important maternal characteristics.     

Methods of gestational age assessment influence the observed association between antiretroviral therapy exposure,preterm delivery,and small-for-gestational age infants: a prospective study in Cape Town,South Africa

PurposeHeterogeneous findings exist on antiretroviral therapy (ART) use in pregnancy and preterm delivery (PTD) or infants born small-for-gestational age (SGA). Whether reported differences may be explained by methods used to ascertain gestational age (GA) has not been explored.MethodsWe enrolled consecutive pregnant women attending a large primary care antenatal clinic in South Africa. Public-sector midwives assessed GA by last menstrual period (LMP) and symphysis-fundal height (SFH). Separately, if clinical GA was less than 24 weeks, ultrasound (US) was performed by a research sonographer blinded to midwife assessments. In analysis, the impact of measurement error on the association between HIV/ART status and birth outcome by GA method was assessed, and factors associated with clinical GA underestimation or overestimation identified.ResultsIn 1787 women included overall, estimated PTD incidence was 36% by LMP, 17% by SFH, and 11% by US. PTD risk was higher for HIV-infected than HIV-uninfected women using US-GA (adjusted odds ratio [aOR] 1.95; 95% CI 1.10–3.46); for LMP/SFH-GA, the associations were smaller and not significant. These findings persisted after adjustment for age, parity, height, and previous PTD. PTD risk did not vary by timing of ART initiation (before or during pregnancy) for any method. Elevated BMI and older age were associated with decreased risk of underestimation by both LMP and SFH; HIV status and obesity were associated with increased risk of overestimation by SFH. There were no differences in SGA incidence across GA methods.ConclusionsFindings for an association between HIV/ART and birth outcomes are substantially influenced by GA assessment method. With growing public health interest in this association, future research efforts should seek to standardize optimal measures of gestation.     

Menstrual versus clinical estimate of gestational age dating in the United States: temporal trends and variability in indices of perinatal outcomes

Accurate estimation of gestational age early in pregnancy is paramount for obstetric care decisions and for determining fetal growth and other conditions that may necessitate timing the iatrogenic intervention or delivery. We sought to examine temporal changes in the distributions of two measures of gestational age, namely, those based on menstrual dating and a clinical estimate. We further sought to evaluate relative comparisons and variability in indices of perinatal outcomes. We utilised the Natality data files in the US, 1990–2002 comprising women that delivered a singleton livebirth between 22 and 44 weeks gestation ( n  = 42 689 603).
Changes were shown in the distributions of gestational age based on menstrual vs. clinical estimate between 1990 and 2002, as well as changes in the proportions of preterm (<37, <32 and <28 weeks) and post-term (≥42 weeks) birth, and small- (SGA; <10th percentile) and large-for-gestational-age (LGA; birthweight >90th percentile) births. While the absolute rates of preterm birth <37 weeks, SGA and LGA births were lower based on the clinical estimate of gestational age relative to that based on menstrual dating, the increases in preterm birth rate between 1990 and 2002 were fairly similar between the two measures of gestational dating. However, the decline in post-term births was larger, based on the clinical estimate (−73.8%), than on the menstrual estimate (−36.6%) between 1990 and 2002. While the clinical estimate of gestational age appears to provide a reasonably good approximation to the menstrual estimate, disregarding the clinical estimate of gestational age may ignore the advantages of gestational age assessment in modern obstetrics.     

Comparison of gestational age classifications: date of last menstrual period vs. clinical estimate

PURPOSE: The purpose was to compare the two different measures of gestational age currently used on birth certificates (the duration of pregnancy based on the date of last menstrual period [LMP] and the clinical estimate [CE] as related to health status indicators. We contrasted these measures by race/ethnicity. METHODS: NCHS natality files for 2000-2002 were used, selecting cases of single live birth to U.S. resident mothers with both LMP and CE gestational age information. RESULTS: Approximately 75% of the records had valid LMP and CE values and for approximately one-half of these, the LMP and CE values did not exactly agree. Overall and for each race and ethnic group, the LMP measures resulted in higher proportions of very preterm, preterm, postterm and SGA births. CE value provided preterm rates of 7.9% and for LMP, 9.9%. The odds ratio of preterm birth for African-Americans using the CE measure was 1.78 [95% Cl 1.77-1.79]. The odds ratio using LMP was 1.93 [95% Cl 1.92-1.94]. Whites were the referent population. CONCLUSIONS: Different measures of gestational age result in different overall and race-specific rates of very preterm, preterm, postterm, and SGA births. These findings indicate that substituting or combining these measures may have consequences.     

The research implications of the selection of a gestational age estimation method

There are three primary methods of gestational age estimation: dating based on last menstrual period (LMP), ultrasound-based dating and neonatal estimates. We review the strengths and limitations of each method as well as their implications for research. Dating based on LMP is a simple, low-cost method of estimating gestational age. Limitations associated with the use of menstrual-based dating include reporting problems such as uncertainty regarding the LMP date, possibly due to bleeding not associated with menses, as well as concerns about the incidence of delayed ovulation, which can result in invalid estimates of gestation, even for women with certain LMP dates. Given that most women in the US have at least one ultrasound during pregnancy, it is becoming increasingly common for clinicians to verify menstrual dates using early ultrasound. To calculate gestational age with the use of ultrasound, fetal measurements are compared with a gestational age-specific reference. The primary limitation of this method is the fact that the gestational age estimates of symmetrically large or small fetuses will be biased. Further, given that ultrasound references were developed using pregnancies that were dated according to reliable LMP dates, they are potentially biased in the same direction as dates calculated according to LMP. Neonatal estimates of gestational age have been shown to be the least precise dating method. To highlight the research implications of the choice of a gestational dating method, we used data from the Routine Antenatal Diagnostic Imaging with Ultrasound Study to identify risk factors for post-term delivery. Risk factors for post-term delivery are shown to vary according to the choice of a gestational dating method, suggesting that some findings are an artefact of the choice of a method rather than evidence of causality.     

Preterm birth: Case definition & guidelines for data collection,analysis, and presentation of immunisation safety data

Preterm birth is commonly defined as any birth before 37 weeks completed weeks of gestation. An estimated 15 million infants are born preterm globally, disproportionately affecting low and middle income countries (LMIC). It contributes directly to estimated one million neonatal deaths annually and is a significant contributor to childhood morbidity. However, in many clinical settings, the information available to calculate completed weeks of gestation varies widely. Accurate dating of the last menstrual period (LMP), as well as access to clinical and ultrasonographic evaluation are important components of gestational age assessment antenatally. This case definition assign levels of confidence to categorisation of births as preterm, utilising assessment modalities which may be available across different settings. These are designed to enable systematic safety evaluation of vaccine clinical trials and post-implementation programmes of immunisations in pregnancy.     

Optimal gestational age and birth-weight cutoffs to predict neonatal morbidity.

BACKGROUND: Gestational age (GA) and birth weight (BW) criteria are used to identify newborns at risk for neonatal morbidity. Currently, preterm is GA less than 37 weeks; low birth weight is BW less than 2,500 grams; and small for gestational age (SGA) is BW less than the tenth percentile weight for the infant's GA. The optimal classification system balances the misclassification cost of false negatives against the cost of false positives. OBJECTIVE: To calculate the relative misclassification costs implied by the current 37-week and 2,500-gram cutoffs, and to test the validity of the current definition of SGA as a predictor of term morbidities. METHODS: GA, BW, and morbidity information were collected for 22,606 infants born between July 1981 and December 1992. Using this dataset, logistic regression coefficients were obtained modeling GA or BW as predictors of morbidities associated with prematurity. For a subset of 18,813 infants with GAs between 37 and 41 weeks, coefficients were obtained modeling both GA and BW as independent predictors of term morbidities. The logistic regression coefficients were used to calculate optimal birth weight, gestational age, and birth-weight-for-gestational-age cutoffs. RESULTS: The current definitions of low birth weight and preterm imply that it is 18 to 28 times more costly to misclassify a sick infant as low-risk than to misclassify a well infant as high-risk. CONCLUSIONS: Gestational age alone is better than birth weight alone at predicting preterm morbidities. No birth-weight cutoff can adequately predict term morbidities. A single weight-percentile cutoff for all gestational ages should not be used to identify newborns at high risk for neonatal morbidity.     

Hospitalizations in adolescence and early adulthood among Swedish men and women born preterm or small for gestational age

BACKGROUND: Preterm birth and reduced intrauterine growth appear to be related to morbidity in childhood and later adulthood. We studied whether the risk of all-cause hospitalization in adolescence and early adulthood differed between individuals who were born preterm or small for gestational age (SGA) compared with those born at term and appropriate for gestational age. METHODS: Using Swedish registries, we followed 304,275 men and women born in 1973-1975 for any hospitalizations occurring in 1987-1996. Preterm birth was defined as <37 weeks of gestation and SGA as babies smaller than 2 standard deviations below the mean weight for gestational length, according to Swedish standards. We created 3 mutually exclusive categories: "preterm" (<37 weeks and not SGA), "SGA" (SGA and not preterm), and "both preterm and SGA." The comparison group was all term births not SGA. Childhood socioeconomic characteristics were accounted for in the analyses. RESULTS: The overall risk of hospitalization was higher for men and women born SGA (adjusted odds ratio = 1.16; 95% confidence interval = 1.12-1.21), for those born preterm (1.06; 1.02-1.10), and for those born both preterm and SGA (1.42; 1.26-1.59). In addition to higher risks for previously reported adverse health outcomes, such as neurodevelopment sequelae and congenital anomalies, men and women born SGA or preterm were more likely to be hospitalized due to unspecified symptoms. SGA also appeared to be associated with genitourinary diseases and drug use. CONCLUSIONS: Men and women born SGA or preterm were at higher risk for hospitalization during adolescence and early adulthood, with men and women born SGA more at risk than those born preterm.     

上海市0~6岁小于胎龄儿健康及生长发育状况普查

目的 了解上海市0~6岁小于胎龄(small for gestational age,SGA)儿生长发育特点,为其生后保健提供科学依据。方法 通过普查方法对所有于2004年9月1日-2011年10月1日出生的SGA建卡,回顾性调查收集SGA儿童的体检数据,包括身高(2岁以下为身长)、体重、头围、胸围四个指标;分男、女12个年龄点,共计25 431名。儿童SGA分为早产儿及足月儿两类,与适于胎龄儿比较其各年龄段发育水平及增长值。结果 上海市SGA总发病率3.15%,城区发病率约1.87%,郊区发病率约3.42%;SGA 0~6岁期间体格发育水平一直落后于正常儿童;0~6岁三组长速排序为早产儿SGA＞足月儿SGA＞AGA。结论 SGA儿童0~6岁期间均显示追赶生长模式,早产儿SGA具有更大的生长空间。     

Prenatal application of the individualized fetal growth reference

The individualized reference for defining small for gestational age (SGA) at birth has gained popularity in recent years. However, its utility on fetal assessment has not been evaluated. The authors compare an individualized with an ultrasound reference in predicting poor perinatal outcomes. Data from a large clinical trial in predominantly white US women (1987-1991) with singleton pregnancies (n = 9,526) were used. The individualized reference classified fewer SGA fetuses than the ultrasound reference, but the risks of adverse outcomes were similar between fetuses classified by both references. The risk increased substantially only when the percentiles fell below the 5th percentile (likelihood ratio positive at birth = 2.68 (95% confidence interval (CI): 2.00, 3.58) and 3.13 (95% CI: 2.34, 4.18) for ultrasound and individualized references, respectively). SGA fetuses defined by either the individualized or ultrasound reference alone had risk ratios of adverse outcomes of 1.91 (95% CI: 0.77, 4.77) and 1.18 (95% CI: 0.37, 3.77), respectively, compared with normal fetuses (the difference between these 2 risk ratios, P = 0.71). The authors conclude that neither the ultrasound-based nor the individualized reference does well in predicting adverse perinatal outcomes. The 5th percentile may be a better cutpoint than the 10th percentile in defining SGA.     

Variation between last-menstrual-period and clinical estimates of gestational age in vital records

An accurate assessment of gestational age is vital to population-based research and surveillance in maternal and infant health. However, the quality of gestational age measurements derived from birth certificates has been in question. Using the 2002 US public-use natality file, the authors examined the agreement between estimates of gestational age based on the last menstrual period (LMP) and clinical estimates in vital records across durations of gestation and US states and explored reasons for disagreement. Agreement between the LMP and the clinical estimate of gestational age varied substantially across gestations and among states. Preterm births were more likely than term births to have disagreement between the two estimates. Maternal age, maternal education, initiation of prenatal care, order of livebirth, and use of ultrasound had significant independent effects on the disagreement between the two measures, regardless of gestational age, but these factors made little difference in the magnitude of gestational age group differences. Information available on birth certificates was not sufficient to understand this disparity. The lowest agreement between the LMP and the clinical estimate was observed among preterm infants born at 28-36 weeks' gestation, who accounted for more than 90% of total preterm births. This finding deserves particular attention and further investigation.     

早产儿早期血清蛋白生化指标的临床研究

目的 分析早产儿早期血清蛋白生化指标在评价早产儿营养状态的价值。方法 选择早产儿263例,将其中全部适于胎龄(AGA)早产儿(207例)分为28周≤GA≤34周组及34周＜GA＜37周组;将263例28周≤GA≤34周及34周＜GA＜37周两组早产儿分别分为小于胎龄(SGA)及AGA进行比较;根据出生体重分为≤2 000 g组,＞2 000 g组。所有早产儿于出生后24 h内采集静脉血2 ml,检测血清前白蛋白(PA)、白蛋白(ALB)、球蛋白(GLO)水平,并计算血清前白蛋白质量(SPMPA),统计所有早产儿住院时间。结果 小胎龄组SPMPA、ALB、GLO明显低于大胎龄组,差异具有统计学意义(P＜0.05),小胎龄组PA亦较低,但差异无统计学意义(P＞0.05);≤2 000 g组SPMPA、ALB显著低于＞2 000 g组,差异有统计学意义(P＜0.05),PA及GLO均较低,但差异无统计学意义(P＞0.05),SGA组SPMPA均明显低于AGA(P＜0.05);胎龄越小、体重越低,住院时间越长,且SGA住院时间明显增加(P＜0.05);SPMPA与出生体重呈明显正相关(r=0.540,P＜0.05)。结论 早产儿胎龄越小、体重越低,血清前白蛋白质量、白蛋白水平越低;SPMPA是评价早产儿成熟度及营养状况最敏感的指标,还可作为区分SGA和AGA的有效指标。     

Medical termination of pregnancy during the second versus the first trimester and its effects on subsequent pregnancy

Objective

The objective was to compare the risks of preterm birth, low birth weight, small for gestational age (SGA) infants and placental complications in subsequent pregnancy after second vs. first trimester medical termination of pregnancy (MTOP) in primigravid women.

Study Design

A total of 88,522 women who underwent termination of pregnancy during 2000–2009 were identified using Finnish health registers. Of them, primigravid women who underwent MTOP and had subsequent pregnancy ending in live birth up to the end of 2009 (n= 3843) were included in the study. The incidences and risks of preterm birth, low birth weight, SGA infants and placental complications after first- (n= 3427) vs. second-trimester MTOP (n= 416) were compared.

Results

Differences between the study groups in the incidences of preterm birth (3.9% in both groups), low birth weight (3.9% in the second- vs. 3.2% in the first-trimester group), SGA infants (2.4% vs. 2.5%) and placental complications (1.9% vs. 2.6%) were statistically insignificant. Second-trimester MTOP was associated with similar risks of preterm birth, low birth weight, SGA infants and placental complications compared with first-trimester MTOP after adjustment for background characteristics. After second-trimester MTOP, 51.2% of women underwent surgical evacuation, and 4.3% were diagnosed with infection. The differences in the risks of preterm birth, low birth weight, SGA infants and placental complications were statistically insignificant between women with vs. without these complications following second-trimester MTOP.

Conclusions

Second-trimester MTOP among primigravid women did not increase the risks of preterm birth, low birth weight, SGA infants or placental complications in subsequent pregnancy compared with first-trimester MTOP.

Implications

The present study suggests that medical termination of pregnancy in primigravid women during second vs. first trimester does not increase the risks of adverse outcomes in subsequent pregnancy and delivery. The data are of value when counseling women undergoing second-trimester TOP.     

Coffee drinking and risk of preterm birth

OBJECTIVES: We analysed the association between coffee drinking before and during the three trimesters of pregnancy and the risk of preterm birth of babies normal for gestational age (NGA) or small for gestational age (SGA). METHODS: Case-control study conducted in University clinics of North Italy. Cases were 502 women who delivered at <37 weeks of gestation. The controls included 1966 women who gave birth at term (>or=37 weeks of gestation) to healthy infants on randomly selected days at the hospitals where cases had been identified. RESULTS: There was inverse association for coffee consumption in the third trimester of pregnancy in SGA cases compared to NGA (heterogeneity test between OR: chi1(2)=5.6811 P<0.05). In comparison with not drinkers, all the ORs of overall intake of caffeine were closed near the unity for both SGA and NGA preterm birth. CONCLUSION: Compared with no consumption, a low consumption of coffee during pregnancy may not have significant effects on preterm birth.     

The accuracy of using last menstrual period to determine gestational age for first trimester medication abortion: a systematic review

Objective

We sought to evaluate the accuracy of assessing gestational age (GA) prior to first trimester medication abortion using last menstrual period (LMP) compared to ultrasound (U/S).

Study Design

We searched Medline, Embase and Cochrane databases through October 2013 for peer-reviewed articles comparing LMP to U/S for GA dating in abortion care. Two teams of investigators independently evaluated data using standard abstraction forms. The US Preventive Services Task Force and Quality Assessment of Diagnostic Accuracy Studies guidelines were used to assess quality.

Results

Of 318 articles identified, 5 met inclusion criteria. Three studies reported that 2.5–11.8% of women were eligible for medication abortion by LMP and ineligible by U/S. The number of women who underestimated GA using LMP compared to U/S ranged from 1.8 to 14.8%, with lower rates found when the sample was limited to a GA < 63 days. Most women (90.5–99.1%) knew their LMP, 70.8–90.5% with certainty.

Conclusion

Our results support that LMP can be used to assess GA prior to medication abortion at GA < 63 days. Further research looking at patient outcomes and identifying women eligible for medication abortion by LMP but ineligible by U/S is needed to confirm the safety and effectiveness of providing medication abortion using LMP alone to determine GA.     

整合性团体干预对小于胎龄儿体格发育及骨密度的影响

目的 探讨整合性团体干预模式对小于胎龄儿(SGA)体格发育及骨密度的影响,为提高SGA早期干预效果提供理论依据。方法 选择高危儿门诊SGA患儿67例,根据家长意愿分为干预组和非干预组,干预组33例给予整合性团体干预,非干预组34例只进行常规高危儿管理,随机选择同期体检的早产适于胎龄儿20例做对照,于纠正12月SGA干预组和非干预组、早产适于胎龄儿组进行体重、身长、头围及骨密度检测。结果 纠正12月SGA干预组、非干预组、早产适于胎龄儿组体质量、身长、头围及骨密度差异有统计学意义(P<0.05)。早产适于胎龄儿组体重、身长、头围>SGA干预组>SGA非干预组,SGA非干预组骨密度>早产适于胎龄儿组>SGA干预组。结论 整合性团体干预模式能促进SGA体格发育,尤其是体重追赶较快,在追赶过程中,SGA骨密度不足的问题需引起重视,定量超声骨密度检查值得推荐。     

不同胎龄及体重新生儿血Ghrelin、胰岛素样生长因子-1、胰岛素样生长因子结合蛋白-3、胰岛素水平检测分析

目的:探讨Ghrelin与新生儿胰岛素-胰岛素样生长因子轴的关系,进一步揭示其对新生儿生长发育及能量代谢的影响。方法:选择62例新生儿,按胎龄、体重分为足月儿、早产儿、适于胎龄儿(appropriate for gestational age,AGA)和小于胎龄儿(small for gestational age,SGA)。其中胎龄30～34周14例,34+1～37周14例,37+1～41周34例。足月SGA13例,足月AGA 21例。检测血Ghrelin、胰岛素样生长因子-1(insulin-like growth factor-1,IGF-1)、胰岛素样生长因子结合蛋白-3(insulin-like growth factor binding protein-3,IGFBP-3)以及胰岛素、血糖水平,并在各组间进行比较。结果:30～34周、34+1～37周、37+1～41周3组比较Ghrelin浓度分别为(2.238±0.618)ng/ml(、1.226±0.37)ng/ml(、1.036±0.328)ng/ml,早产儿Ghrelin水平明显高于足月儿(P<0.01),且随着胎龄的增大差距减小;IGF-1分别为(43.214±16.723)ng/ml、(115.579±30.136)ng/ml、(153.292±26.633)ng/ml,IGFBP-3分别为(70.814±22.603)ng/ml、(123.300±28.666)ng/ml、(157.214±38.990)ng/ml,胰岛素分别为(1.032±0.812)μU/ml、(5.534±2.273)μU/ml、(14.654±3.064)μU/ml。IGF-1、IGFBP-3、胰岛素水平早产儿明显低于足月儿(P<0.01),足月SGA的Ghrelin水平明显高于AGA(P<0.01),IGF-1、IGFBP-3、胰岛素水平明显低于AGA(P均<0.01)。各组血糖水平无明显差异(P>0.05)。在SGA和AGA组Ghrelin分别与IGF-1、IGFBP-3及胰岛素呈明显负相关(P<0.01)。结论:SGA新生儿存在胰岛素-IGF轴的损害,IGF-1与胰岛素水平低下,从而使Ghrelin浓度反馈性的升高,以代偿其能量代谢的负平衡。     

Assessing number-specific error in the recall of onset of last menstrual period

The goal of this investigation was to determine whether women who did not report preferred numbers for their last menstrual period (LMP) may be a group of women who are particularly careful in keeping track of their menstrual cycles and therefore have more accurate LMP dating--based on a comparison with ultrasound examinations. We also sought to estimate the frequency with which preferred numbers are reported in different sources of data and for different subgroups of women. First, we examined the 1987 California birth certificates in which LMP was collected at the time of birth (n = 504853). We also examined the records of 43880 women participating in the California Alpha-fetoprotein (AFP) Screening Program between 1986 and 1987, for whom gestational ages based on both early ultrasound examination and LMP were collected before 20 weeks of gestation. In the 1987 California birth certificates, seven numbers--1, 5, 10, 15, 20, 25 and 28--were recorded more frequently than expected. An estimated 12.9% of these records had preferred numbers. The most frequently recorded number was 15, occurring 2.5 times more often than expected (P < 0.01). In the data of the AFP Screening Program, the same seven numbers were preferred, and approximately 7.9% of records were affected by number preference. Comparisons with measurements of gestational age based on ultrasound demonstrated that LMP-based gestational ages in which non-preferred numbers are reported for the LMP are slightly more accurate than those in which preferred numbers are reported (P < 0.01). In most cases, number preference appears to introduce small errors into measurements of gestational age, probably as a result of rounding. Thus, the effect of number preference may be primarily of interest to research studies in which small errors in the measurement of gestational age will have a significant impact on findings.     

Maternal nutrition and spontaneous preterm birth.

Previous studies suggesting that maternal undernutrition increases the risk of preterm birth have suffered from several methodological shortcomings, including use of total gestational weight gain rather than net rate of gain in maternal tissue, inclusion of induced preterm deliveries, and error-prone gestational age measurements based solely on menstrual dates. The authors have attempted to overcome these shortcomings by investigating the potential etiologic roles of prepregnancy body mass index, net rate of maternal weight gain, height, and a number of other potential biological and sociodemographic determinants of spontaneous (i.e., noninduced) preterm birth in a cohort of 13,102 women with early ultrasound-confirmed gestational age who delivered at the Royal Victoria Hospital in Montreal, Quebec, Canada, between January 1, 1980 and March 31, 1989. Total weight gain, but not body mass index, was highly significantly associated with spontaneous preterm birth, averaging 14.6, 12.5, 9.9, and 9.1 kg, in women delivering at 37 or more, less than 37, less than 34, and less than 32 completed weeks, respectively. Although the relation persisted when weight gain was expressed as an overall rate, it disappeared when the analysis was based on net rate; mean net rates of gain were 0.28, 0.29, 0.27, and 0.27 kg/week, respectively. On the basis of multiple logistic regression analyses, significant determinants of birth at less than 37 weeks included maternal short stature; noncompletion of high school; unmarried status; smoking; diabetes; urinary tract infection within 2 weeks of delivery; prepregnancy hypertension; severe pregnancy-induced hypertension; and previous history of preterm delivery, low birth weight, or neonatal death. Most of these factors retained their significance for birth at less than 34 and less than 32 weeks. In fact, the effect of low maternal education was even stronger at these more severe "levels" of preterm birth. The authors conclude that prepregnancy weight-for-height and gestational weight gain are not important determinants of spontaneous preterm birth and that some previous studies have mistaken an effect of shortened gestation for its cause. Other biologic and social determinants, however, indicate priorities for future research and intervention.     

Characteristics of Gut Microbiota in Small for Gestational Age Infants with Very Low Birth Weight

Small for gestational age (SGA) birth is associated with high rates of mortality and morbidity in preterm infants. The aim of this preliminary observational study was to investigate the difference in gut microbiota between SGA and appropriate for gestational age (AGA) preterm infants with very low birth weight (VLBW). We included 20 VLBW preterm infants (SGA, n = 10; AGA, n = 10) in this study. Stool samples were collected on days 7, 14, and 30 after birth. We performed 16S ribosomal DNA sequencing to compare microbiota composition between both groups. The SGA group exhibited a lower abundance of Klebsiella on day 14 (SGA, 0.57%; AGA, 7.42%; p = 0.037). On day 30, the SGA group exhibited a lower abundance of Klebsiella (SGA 3.76% vs. AGA 16.05%; p = 0.07) and Enterobacter (SGA 5.09% vs. AGA 27.25%; p = 0.011) than the AGA group. Beta diversity demonstrated a separation of the bacterial community structure between both groups on day 30 (p = 0.019). The present study revealed that a distinct gut microbiota profile gradually develops in SGA preterm infants with VLBW during the early days of life. The role of changes in gut microbiota structure warrants further investigation.