Birthweight charts customised for maternal height optimises the classification of small and large-for-gestational age newborns

AIM

To construct birthweight charts customised for maternal height and evaluate the effect of customization on SGA and LGA classification.

METHODS

Data were extracted (n = 21 350) from the MiCaS project in the Netherlands (2012-2020). We constructed the MiCaS-birthweight chart customised for maternal height using Hadlock's method. We defined seven 5-centimetre height categories from 153 to 157 cm until 183-187 cm and calculated SGA and LGA prevalences for each category, using MiCaS and current Dutch birthweight charts.

RESULTS

The MiCaS-chart showed substantially higher birthweight values between identical percentiles with increasing maternal height. In the Dutch birthweight chart, not customised for maternal height, the prevalence of SGA (p90) increased with increasing height category, from 1.4% in the lowest height category to 21.8% in the highest category (range 20.4%). In the MiCaS-birthweight chart, SGA and LGA prevalences were more constant across maternal heights, similar to overall prevalences (SGA range 3.3% and LGA range 1.7%).

CONCLUSION

Compared to the current Dutch birthweight chart, the MiCaS-birthweight chart customised for maternal height shows a more even distribution of SGA and LGA prevalences across maternal heights.

The smaller firstborn: exploring the association of parity and fetal growth

PURPOSE

To investigate the association of parity with a range of neonatal anthropometric measurements in a cohort of uncomplicated term singleton pregnancies.

METHODS

Retrospective cohort study of patients with a singleton term birth at a single tertiary center (2014-2020) was carried out. The primary exposure was parity. The following neonatal anthropometric measures were considered: birthweight, head circumference, length, ponderal index, and neonatal body mass index (BMI).

RESULTS

A total of 8134 patients met the study criteria, 1949 (24.0%) of whom were nulliparous. Compared with multiparous patients, infants of nulliparous patients had a lower mean percentile for birthweight (43.1 ± 26.4 vs. 48.3 ± 26.8 percentile, p < 0.001), head circumference (44.3 ± 26.4 vs. 48.1 ± 25.5 percentile, p < 0.001), length (52.6 ± 25.1 vs. 55.5 ± 24.6 percentile, p < 0.001), ponderal index (34.4 ± 24.0 vs. 37.6 ± 24.2 percentile, p < 0.001), and BMI (39.1 ± 27.1 vs. 43.9 ± 27.3 percentile, p < 0.001). In addition, infants of nulliparous patients had higher odds of having a small (< 10th percentile for gestational age) birthweight (aOR 1.32 [95% CI 1.12-1.56]), head circumference (aOR 1.54 [95% CI 1.29-1.84]), length (aOR 1.50 [95% CI 1.16-1.94]), ponderal index (aOR 1.30 [95% CI 1.12-1.51]), and body mass index (aOR 1.42 [95% CI 1.22-1.65]). Most neonatal anthropometric measures increased with parity until a parity of 2, where it seemed to reach a plateau.

CONCLUSION

Parity has an independent impact on a wide range of neonatal anthropometric measures, suggesting that parity is associated with both fetal skeletal growth and body composition. In addition, the association of parity with fetal growth does not follow a continuous relationship but instead reaches a plateau after the second pregnancy.

Maternal risk factors associated with term low birth weight in India: A review

Low birth weight is one of the leading factors for infant morbidity and mortality. To a large extent affect, various maternal risk factors are associated with pregnancy outcomes by increasing odds of delivering an infant with low birth weight. Despite this association, understanding the maternal risk factors affecting term low birth weight has been a challenging task. To date, limited studies have been conducted in India that exert independent magnitude of these effects on term low birth weight. The aim of this review is to examine the current knowledge of maternal risk factors that contribute to term low birth weight in the Indian population. In order to identify the potentially relevant articles, an extensive literature search was conducted using PubMed, Goggle Scholar and IndMed databases (1993 – Dec 2020). Our results indi­cate that maternal age, educational status, socio-economic status, ethnicity, parity, pre-pregnancy weight, maternal stature, maternal body mass index, obstetric history, maternal anaemia, gestational weight gain, short pregnancy outcome, hypertension during pregnancy, infection, antepartum haemorrhage, tobacco consumption, maternal occupation, maternal psychological stress, alcohol consumption, antenatal care and mid-upper arm circumference have all independent effects on term low birth weight in the Indian pop­ulation. Further, we argue that exploration for various other dimensions of maternal factors and underlying pathways can be useful for a better understanding of how it exerts independent association on term low birth weight in the Indian sub-continent.

Parity-Adjusted Term Neonatal Growth Chart Modifies Neonatal Morbidity and Mortality Risk Stratification

Objective: To investigate the impact of parity-customized versus population-based birth weight charts on the identification of neonatal risk for adverse outcomes in small (SGA) or large for gestational age (LGA) infants compared to appropriate for gestational age (AGA) infants. Study design: Observational, retrospective, cohort study based on electronic medical birth records at a single center between 2006 and 2017. Neonates were categorized by birth weight (BW) as SGA, LGA, or AGA, with the 10th and 90th centiles as boundaries for AGA in a standard population-based model adjusted for gestational age and gender only (POP) and a customized model adjusted for gestational age, gender, and parity (CUST). Neonates defined as SGA or LGA by one standard and not overlapping the other, are SGA/LGA CUST/POP ONLY. Analyses used a reference group of BW between the 25th and 75th centile for the population. Results: Overall 132,815 singleton, live, term neonates born to mothers with uncomplicated pregnancies were included. The customized model identified 53% more neonates as SGA-CUST ONLY who had significantly higher rates of morbidity and mortality compared to the reference group (OR = 1.33 95% CI [1.16−1.53]; p < 0.0001). Neonates defined as LGA by the customized model (LGA-CUST) and AGA by the population-based model LGA-CUST ONLY had a significantly higher risk for morbidity compared to the reference (OR = 1.36 95% CI [1.09−1.71]; p = 0.007) or the LGA POP group. Neonatal mortality only occurred in the SGA and AGA groups. Conclusions: The application of a parity-customized only birth weight chart in a population of singleton, term neonates is a simple platform to better identify birth weight related neonatal risk for morbidity and mortality.

From population reference to national standard: new and improved birthweight charts

BACKGROUND

Antenatal detection of intrauterine growth restriction remains a major obstetrical challenge, with the majority of cases not detected before birth. In these infants with undetected intrauterine growth restriction, the diagnosis must be made after birth. Clinicians use birthweight charts to identify infants as small-for-gestational-age if their birthweights are below a predefined threshold for gestational age. The choice of birthweight chart strongly affects the classification of small-for-gestational-age infants and has an impact on both research findings and clinical practice. Despite extensive literature on pathological risk factors associated with small-for-gestational-age, controversy exists regarding the exclusion of affected infants from a reference population.

OBJECTIVE

This study aims to identify pathological risk factors for abnormal fetal growth, to quantify their effects, and to use these findings to calculate prescriptive birthweight charts for the Dutch population.

MATERIALS AND METHODS

We performed a retrospective cross-sectional study, using routinely collected data of 2,712,301 infants born in The Netherlands between 2000 and 2014. Risk factors for abnormal fetal growth were identified and categorized in 7 groups: multiple gestation, hypertensive disorders, diabetes, other pre-existing maternal medical conditions, maternal substance (ab)use, medical conditions related to the pregnancy, and congenital malformations. The effects of these risk factors on mean birthweight were assessed using linear regression. Prescriptive birthweight charts were derived from live-born singleton infants, born to ostensibly healthy mothers after uncomplicated pregnancies and spontaneous onset of labor. The Box-Cox-t distribution was used to model birthweight and to calculate sex-specific percentiles. The new charts were compared to various existing birthweight and fetal-weight charts.

RESULTS

We excluded 111,621 infants because of missing data on birthweight, gestational age or sex, stillbirth, or a gestational age not between 23 and 42 weeks. Of the 2,599,640 potentially eligible infants, 969,552 (37.3%) had 1 or more risk factors for abnormal fetal growth and were subsequently excluded. Large absolute differences were observed between the mean birthweights of infants with and without these risk factors, with different patterns for term and preterm infants. The final low-risk population consisted of 1,629,776 live-born singleton infants (50.9% male), from which sex-specific percentiles were calculated. Median and 10th percentiles closely approximated fetal-weight charts but consistently exceeded existing birthweight charts.

CONCLUSION

Excluding risk factors that cause lower birthweights results in prescriptive birthweight charts that are more akin to fetal-weight charts, enabling proper discrimination between normal and abnormal birthweight. This proof of concept can be applied to other populations.

New birthweight charts according to parity and type of delivery for the Spanish population

OBJECTIVE

Birthweight by gestational age charts enable fetal growth to be evaluated in a specific population. Given that maternal profile and obstetric practice have undergone a remarkable change over the past few decades in Spain, this paper presents new Spanish reference percentile charts stratified by gender, parity and type of delivery. They have been prepared with data from the 2010-2014 period of the Spanish Birth Statistics Bulletin.

METHODS

Reference charts have been prepared using the LMS method, corresponding to 1,428,769 single, live births born to Spanish mothers. Percentile values and mean birth weight are compared among newborns according to gender, parity and type of delivery.

RESULTS

Newborns to primiparous mothers show significantly lower birthweight than those born to multiparous mothers (p<0.036). Caesarean section was associated with a substantially lower birthweight in preterm births (p<0.048), and with a substantially higher birthweight for full-term deliveries (p<0.030). Prevalence of small for gestational age is significantly higher in newborns born by Caesarean section, both in primiparous (p<0.08) and multiparous mothers (p<0.027) and, conversely, the prevalence of large for gestational age among full-term births is again greater both in primiparous (p<0.035) and in multiparous mothers (p<0.007).

CONCLUSIONS

Results support the consideration of establishing parity and type of delivery-specific birthweight references. These new charts enable a better evaluation of the impact of the demographic, reproductive and obstetric trends currently in Spain on fetal growth.

Does the Presence of Risk Factors for Fetal Growth Restriction Increase the Probability of Antenatal Detection? A French National Study

BACKGROUND

Screening for fetal growth restriction (FGR) is a major component of prenatal care. We investigated whether the presence of maternal and pregnancy risk factors for FGR improves the antenatal suspicion of FGR for infants born small-for-gestational age (SGA) as well as their impact on screening specificity.

METHODS

Data are from a representative sample of births from the 2010 French National Perinatal Survey (n = 14 100). Detection of FGR was determined by a suspicion of FGR noted in medical charts. Analyses were performed for singleton infants with birthweight under the 10th percentile (SGA), under the 3rd percentile (severely SGA), and above the 10th percentile (false positives) of French references. We studied risk factors for FGR (medical and obstetric conditions, advanced maternal age, nulliparity, body mass index and smoking) using multivariable Poisson regression to derive adjusted risk ratios (aRR).

RESULTS

Of SGA infants, 21.7% were suspected of FGR. The presence of obstetric and medical risk factors for FGR was associated with higher suspicion among SGA infants [RR 2.1, 95% confidence interval (CI) 1.7, 2.7]. However, despite the presence of these factors, 60% and 40% of SGA and severely SGA infants, respectively, were not suspected of FGR. Two per cent of normal birthweight infants were suspected of FGR, increasing to 5% when obstetric and medical risk factors were present. Smoking and older maternal age were unrelated to suspicion while females were more likely to be suspected of FGR.

CONCLUSION

Our results suggest that better risk assessment could improve antenatal identification of FGR. Sex-specific fetal growth references should be used to avoid systematic bias linked to sex.

Customized versus Population-Based Birth Weight References for Predicting Fetal and Neonatal Undernutrition

Objectives: The aim of our study was to construct a model of customized birth weight curves based on a Spanish population and to compare the ability of this customized model to our population-based chart to predict a neonatal ponderal index (PI) <10th percentile. Methods: We developed a model that can predict the 10th percentile for a fetus according to gestational age and gender as well as maternal weight, height, and age. We compared the ability of this customized model to that of our own population-based model to predict a neonatal PI <10th percentile. Data from a large database were used (32,854 live newborns, from 1993 through 2012). Only singleton pregnancies with a gestational age at delivery of 32-42 weeks were included. Results: In the entire pregnant population, the customized method was superior to the population-based method for detecting newborns with a PI <10th percentile (sensitivity: 55 vs. 40.96%; specificity: 99.6 vs. 91.23%; positive predictive value: 11.49 vs. 9.55%, and negative predictive value: 98.84 vs. 98.55%, respectively). In pregnant women with a BMI >90th percentile, the sensitivity was 75%, compared to 50% in the population-based method. In pregnant women with a height >90th percentile, the sensitivity was almost as high as in the population-based method (61.53 vs. 33.33%). Conclusion: The customized birth weight curve is superior to the population-based method for the detection of newborns with a PI <10th percentile. This is especially the case in women in the higher scales of height and weight as well as in preterm babies.

Assessment of fetal growth by customized growth charts

Customized fetal growth charts take account of the individual variation in the fetal growth potential based on non-pathological maternal and fetal characteristics. Application of these customized weight charts might improve the distinction between pathological growth-restricted fetuses and fetuses that are small but have reached their growth potential. Current models for customized growth standards have been based on birth weight and fetal growth data. Variables used for customization are gestational age, maternal age, parity, ethnicity, height, weight and fetal sex. Thus far, it remains controversial whether these maternal and fetal characteristics used for customization are strong enough predictors for fetal growth on an individual level and are truly physiological characteristics. The currently available customized growth charts might be of benefit for use in epidemiological studies and clinical practice. Further studies are needed to validate these customized growth models and to examine whether and to what extend they improve identification of children that are at risk for morbidity in the perinatal period and later in life.

The association between parity and birthweight in a longitudinal consecutive pregnancy cohort

BACKGROUND

Nulliparity is associated with lower birthweight, but few studies have examined how within-mother changes in risk factors impact this association.

METHODS

We used longitudinal electronic medical record data from a hospital-based cohort of consecutive singleton live births from 2002-2010 in Utah. To reduce bias from unobserved pregnancies, primary analyses were limited to 9484 women who entered nulliparous from 2002-2004, with 23,380 pregnancies up to parity 3. Unrestricted secondary analyses used 101,225 pregnancies from 45,212 women with pregnancies up to parity 7. We calculated gestational age and sex-specific birthweight z-scores with nulliparas as the reference. Using linear mixed models, we estimated birthweight z-score by parity adjusting for pregnancy-specific sociodemographics, smoking, alcohol, prepregnancy body mass index, gestational weight gain, and medical conditions.

RESULTS

Compared with nulliparas', infants of primiparas were larger by 0.20 unadjusted z-score units [95% confidence interval (CI) 0.18, 0.22]; the adjusted increase was similar at 0.18 z-score units [95% CI 0.15, 0.20]. Birthweight continued to increase up to parity 3, but with a smaller difference (parity 3 vs. 0 β = 0.27 [95% CI 0.20, 0.34]). In the unrestricted secondary sample, there was significant departure in linearity from parity 1 to 7 (P < 0.001); birthweight increased only up to parity 4 (parity 4 vs. 0 β = 0.34 [95% CI 0.31, 0.37]).

CONCLUSIONS

The association between parity and birthweight was non-linear with the greatest increase observed between first- and second-born infants of the same mother. Adjustment for changes in weight or chronic diseases did not change the relationship between parity and birthweight.

Risk factors for perinatal death in two different levels of care: a case-control study

BACKGROUND

According to the World Health Organization, there are over 6.3 million perinatal deaths (PND) a year worldwide. Identifying the factors associated with PND is very helpful in building strategies to improve the care provided to mothers and their babies.

OBJECTIVE

To investigate the maternal, gestational and neonatal factors associated with PND at two different levels of care.

METHODS

Case-control study including 299 PND cases and 1161 infants that survived the early neonatal period (controls) between 2001-2006 in two hospitals at different care levels (secondary and tertiary) located in southeastern Brazil. Correlations between study variables and PND were evaluated by univariate analysis. PND-related variables were included in a multiple logistic regression model, and independent estimates of PND risk were obtained.

RESULTS

Although five-minute Apgar score <7, low birthweight and maternal hemorrhage were associated with PND in the secondary care center, no independent risk factors were identified at this level of care. In the tertiary hospital, PND was positively associated with primiparity, male sex, prematurity, low 5-minute Apgar score, and pregnancy complicated by arterial hypertension or intrauterine infection.

CONCLUSIONS

Several risk factors positively associated with PND were indentified in the tertiary, but not in the secondary care level hospital. Since most of the risk factors herein identified are modifiable through effective antenatal and intrapartum care, greater attention should be given to preventive strategies.

Depression and anxiety in women during pregnancy and neonatal outcome: data from the EDEN mother-child cohort

BACKGROUND

According to the World Health Organization, mental health disorders are the leading causes of disease burden in women from 15 to 44 years. These conditions in pregnant women may affect the offspring.

AIM

To analyze the relation between depression and anxiety of pregnant women and neonatal outcomes including gestational age and birthweight.

STUDY DESIGN

Observational cohort study.

SUBJECTS

2002 women recruited before the 20th gestational week.

OUTCOME MEASURES

Gestational age at delivery in completed weeks of amenorrhea and preterm delivery defined as birth before 37 completed weeks of gestation. Spontaneous preterm birth (PB) defined as either spontaneous preterm labor or preterm premature rupture of the membranes. Medically indicated preterm delivery defined as delivery that begins by induction or cesarean section. Birthweight as a continuous variable and centiles of the customized fetal weight norms for the French population.

RESULTS

From the 1719 women included in the study, 7.9% (n=135) were classified as "anxious", 11.8% (n=203) as "depressed", 13.2% (n=227) as "depressed and anxious". After adjusting for potential confounders, depression combined with anxiety during pregnancy increased the risk of spontaneous PB (Odds Ratio: 2.46 [1.22-4.94]), but did not influence medically indicated PB nor birthweight.

CONCLUSION

In this study, comorbidity of depressive and anxiety symptoms was the worst condition during pregnancy. Further studies are needed to investigate depression and anxiety together to improve the comprehension of the biological modifications involved.

Association of number of live births with left ventricular structure and function. The Multi-Ethnic Study of Atherosclerosis (MESA)

BACKGROUND

Pregnancy is associated with marked maternal cardiovascular/hemodynamic changes. A greater number of pregnancies may be associated with long-term subclinical changes in left ventricular (LV) remodeling.

METHODS

Among 2,234 white, black, Hispanic, and Chinese women (mean age 62 years) in the MESA, we used linear regression to relate live births and cardiac magnetic resonance imaging LV measures. Covariates included age, ethnicity, height, income, education, birth country, smoking, menopause, and oral contraceptive duration. Models were additionally adjusted for potential mediators: systolic blood pressure, antihypertensive use, total/high-density lipoprotein cholesterol, triglycerides, diabetes, and body mass index. We performed sensitivity analyses excluding 763 women in the lowest socioeconomic group: annual income <$25,000 and lower high school level of education.

RESULTS

With each live birth, LV mass increased 1.26 g; LV end-diastolic volume, 0.74 mL; and LV end-systolic volume, 0.45 mL; LV ejection fraction decreased 0.18% (P trend <0.05). Changes were most notable for the category of women with ≥5 pregnancies. Upon adjustment for potential biologic mediators, live births remained positively associated with LV mass and end-systolic volume. Live births remained significantly associated with LV end-systolic, end-diastolic volumes, and LV mass (P trend ≤0.02) after excluding women in the lowest socioeconomic group.

CONCLUSIONS

Number of live births is associated with key LV structural and functional measures in middle to older ages, even after adjustment for sociodemographic factors and cardiovascular disease risk factors. Hemodynamic changes during pregnancy may be associated with cardiac structure/function beyond childbearing years.

Influence of fetal and parental factors on intrauterine growth measurements: results of the EDEN mother-child cohort

OBJECTIVE

In small-for-gestational-age neonates, parental and fetal characteristics can be used to distinguish between constitutionally small size and growth restriction, which is associated with a higher risk of morbidity and mortality. The aim of this study was to quantify relationships of parental and fetal characteristics with fetal ultrasound measurements.

METHODS

The EDEN mother-child cohort included 2002 pregnant women with singleton pregnancies attending one of two university hospitals. Data from two routine ultrasound examinations for fetal biometry were recorded, at 20-25 and 30-35 weeks of gestation. Biparietal diameter (BPD), head circumference (HC), femur length (FL), abdominal circumference (AC) and estimated fetal weight (EFW) were studied as a function of prepregnancy maternal body mass index (BMI), maternal height, paternal height, fetal sex and gestational age.

RESULTS

Data were obtained at the first scan from 1833 women and at the second scan from 1752 women. Parental anthropometric characteristics were significantly associated with ultrasound measurements at both scans. Maternal BMI was more strongly associated with AC and EFW, whereas both maternal and paternal height were more strongly associated with FL. An association was also found between fetal sex and all ultrasound measurements other than FL.

CONCLUSION

Maternal and paternal anthropometric characteristics are significantly associated with ultrasound measurements in mid to late pregnancy. These relationships provide support for the use of these characteristics in ultrasound fetal size reference charts.

Reduced birthweight in short or primiparous mothers: physiological or pathological?

OBJECTIVE

Customisation of birthweight-for-gestational-age standards for maternal characteristics assumes that variation in birth weight as a result of those characteristics is physiological, rather than pathological. Maternal height and parity are among the characteristics widely assumed to be physiological. Our objective was to test that assumption by using an association with perinatal mortality as evidence of a pathological effect.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

A total of 952 630 singletons born at > or =28 weeks of gestation in the period 1992-2001.

METHODS

We compared perinatal mortality among mothers of short stature (<160 cm) versus those of normal height (> or =160 cm), and primiparous versus multiparous mothers, using an internal reference of estimated fetal weight for gestational age. The total effects of maternal height and parity were estimated, as well as the effects of height and parity independent of birthweight (controlled direct effects). All analyses were based on fetuses at risk, using marginal structural Cox models for the estimation of total and controlled direct effects.

MAIN OUTCOME MEASURES

Perinatal mortality, stillbirth, and early neonatal mortality.

RESULTS

The estimated total effect (HR; 95% CI) of short stature on perinatal death among short mothers was 1.2 (95% CI 1.1-1.3) compared with women of normal height; the effect of short stature independent of birthweight (controlled direct effect) was 0.8 (95% CI 0.6-1.0) among small-for-gestational-age (SGA) births, but 1.1 (95% CI 1.0-1.3) among non-SGA births. Similar results were observed for primiparous mothers.

CONCLUSIONS

The effect of maternal short stature or primiparity on perinatal mortality is partly mediated through SGA birth. Thus, birthweight differences resulting from these maternal characteristics appear not only to be physiological, but also to have an important pathological component.

Parity and risk of later-life maternal cardiovascular disease

BACKGROUND

Prior studies relating parity with maternal cardiovascular disease (CVD) have been performed in relatively small study samples without accounting for pregnancy-related complications associated with CVD.

METHODS

We examined the associations between parity and maternal risk of later-life CVD in a population-based cohort study using data from the Swedish population registers. Women born from 1932 to 1955 were followed until the occurrence of CVD, death, emigration, or end of follow-up (December 31, 2005). Cox proportional hazards models were used to estimate associations between parity and risk of CVD accounting for birth year, yearly income, education level, country of birth, hypertension (pregestational hypertension or gestational hypertension, with or without proteinuria), diabetes (type 1, type 2, or gestational diabetes), preterm birth, small for gestational age, and stillbirth.

RESULTS

During a median follow-up time of 9.5 years (range 0-23.5), there were 65,204 CVD events in the full sample of women. Among 1,332,062 women, parity was associated with CVD in a J-shaped fashion, with 2 births representing the nadir of risk (global P value < .0001). Upon accounting for pregnancy-related complications in a subset of women with at least 1 childbirth after 1973 (n = 590,725), the association of parity with CVD was similar. Compared with women with 2 childbirths, the multivariable-adjusted hazard ratios (95% CIs) for women with 1 and >/=5 births were 1.09 (1.03-1.15) and 1.47 (1.37-1.57), respectively.

CONCLUSIONS

In conclusion, parity was associated with incident maternal CVD in a J-shaped fashion, even after accounting for socioeconomic factors and pregnancy-related complications.

The value of customised centiles in assessing perinatal mortality risk associated with parity and maternal size

OBJECTIVE

We wanted to compare customised and population standards for defining smallness for gestational age (SGA) in the assessment of perinatal mortality risk associated with parity and maternal size.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

Swedish Birth Registry database 1992-1995 with 354 205 complete records.

METHOD

Coefficients were derived and applied to determine SGA by the fully customised method, or by adjustment for fetal sex only, and using the same fetal weight standard.

MAIN OUTCOME MEASURE

Perinatal deaths and rates of small for gestational age (SGA) babies within subgroups stratified by parity, body mass index (BMI) and maternal size within the BMI range of 20.0-24.9.

RESULTS

Perinatal mortality rates (PMR) had a U-shaped distribution in parity groups, increased proportionately with maternal BMI, and had no association with maternal size within the normal BMI range. For each of these subgroups, SGA rates determined by the customised method showed strong association with the PMR. In contrast, SGA based on uncustomised, population-based centiles had poor correlation with perinatal mortality. The increased perinatal mortality risk in pregnancies of obese mothers was associated with an increased risk of SGA using customised centiles, and a decreased risk of SGA using population-based centiles.

CONCLUSION

The use of customised centiles to determine SGA improves the identification of pregnancies which are at increased risk of perinatal death.