Effects of applying universal fetal growth standards in a Scandinavian multi-ethnic population

Low Antenatal Care Number of Consultations Is Associated with Gestational Weight Gain and Birth Weight of Offspring of Teenage Mothers: A Study Based on Colombian and Mexican Cohorts

BACKGROUND

More than 70% of pregnant adolescents in developing countries experience inappropriate gestational weight gain (GWG).

OBJECTIVE

To determine the association of the number of antenatal care visits (ANC) with GWG, birth weight, and their differences between two countries.

METHODS

A prospective study was conducted in two cohorts of adolescents, one from Mexico and one from Colombia. The study calculated pregestational body mass index (BMI), obtained GWG and birth weight, and collected socioeconomic characteristics. Birth weight was categorized according to gestational age. A total of 690 mother-child pairs were included, of which 42.6% were Colombian and 57.4% Mexican.

RESULTS

The study found no association between socioeconomic characteristics and GWG or birth weight. Colombian adolescents were more likely to experience insufficient GWG (68%), compared with 36% of Mexican adolescents. Colombian adolescents who attended fewer than eight ANC visits were at increased risk of insufficient GWG, whereas Mexican adolescents were at increased risk of excessive GWG. Mexican adolescents who began their pregnancies overweight or obese were at increased risk of excessive GWG. Fewer than eight ANC visits were associated with small for gestational age (SGA) in the Mexican cohort.

CONCLUSIONS

Inadequate numbers of ANC visits were associated with excessive and insufficient GWG, and SGA. Promoting ANC in adolescent pregnancy is essential to prevent suboptimal GWG and SGA. This study highlights the need for interventions targeting pregnant adolescents from low socioeconomic backgrounds, prioritizing early initiation of prenatal care (first trimester) and a drastic reduction in the high rates of cesarean sections in this group.

Selecting a birth weight standard for an indigenous population in a LMIC: A prospective comparative study

OBJECTIVES

The aim of the present study was to compare birth weight (BW) distribution and proportion of BWs below or above specified percentiles in low-risk singleton pregnancies in healthy South African (SA) women of mixed ancestry with expected values according to four BW references and to determine the physiological factors affecting BW.

METHODS

This was an ancillary study of a prospective multinational cohort study, involving 7060 women recruited between August 2007 and January 2015 in two townships of Cape Town, characterized by low socioeconomic status, and high levels of drinking and smoking. Detailed information about maternal and pregnancy characteristics, including harmful exposures, was gathered prospectively, allowing us to select healthy women with uncomplicated pregnancies without any known harmful exposures. In this cohort we compared the median BW and the proportion of BWs P90, 95 and 97 according to four reference standards (INTERGROWTH-21st, customized according to the method described by Mickolajczyk, Fetal Medicine Foundation and revised Fenton reference) with expected values. Appropriate parametric and nonparametric tests were used, and sensitivity analysis was performed for infant sex, first trimester bookings and women of normal body mass index (BMI). Multiple regression was used to explore effects of confounders. Written consent and ethics approval was obtained.

RESULTS

The cohort included 739 infants. The INTERGROWTH-21st standard was closest for the actual BW-distribution and categories. Below-expected BW was associated with boys, younger, shorter, leaner women, lower parity and gravidity. Actual BW was significantly influenced by maternal weight, BMI, parity and gestational age.

CONCLUSION

Of the four references assessed in this study, the INTERGROWTH-21st standard was closest for the actual BW distribution. Maternal variables significantly influence BW.

Can the Pfannenstiel skin incision length be adjusted according to the fetal head during elective cesarean delivery?

Objective

The study aims to determine whether the Pfannenstiel skin incision can be adjusted according to the fetal head's occipitofrontal diameter (OFD) during primary cesarean delivery.

Background

Eligible 114 nulliparous women delivered at term by cesarean section in which Pfannenstiel skin incision was performed according to the OFD of the fetal head between June 2017 and September 2021 were included. Excluded cases were non-vertex presentations, all emergency cesarean sections, severe preeclampsia, women in an active phase of the first stage of labor and second stage of labor, placenta previa and low-lying placenta, multiple pregnancies, and uncontrolled gestational diabetes mellitus.

Results

Among 114 eligible nulliparous women, the mean OFD was 116.1 ± 7.2 (99-138) mm, and the measurement of the Pfannenstiel skin incision length, which was performed according to the OFD was found to be 122.8 ± 9.2 (100-155) mm. The difference between OFD and Pfannenstiel incision kept remained within 10 mm in 90 (82.5.2%), 10-20 mm in 17 (15.5%), and more than 20 mm in two women (1.8%). This technique was successful in 109 (95.6%) out of 114 women without extending the skin incision. In five women, skin incision needed to be extended up to 38 mm. In 10 women (8.7%), the rectus abdominis muscle was cut partially to deliver the fetal head. The mean fetal umbilical artery pH was 7.33 ± 0.05. No neonatal hypoxia was encountered in the study.

Conclusion

Pfannenstiel skin incision can be adjusted according to the OFD with minimal margins of error. This technique may provide better cosmetic results by avoiding unnecessarily prolonged incisions with similar newborn outcomes.

Clinical Trial Registration

Clinicaltrials.gov, identifier [NCT05632796].

Regional references vs. international standards for assessing weight and length by gestational age in Lithuanian neonates

Introduction

There is no global consensus as to which standards are the most appropriate for the assessment of birth weight and length. The study aimed to compare the applicability of regional and global standards to the Lithuanian newborn population by sex and gestational age, based on the prevalence of small or large for gestational age (SGA/LGA).

Materials and Methods

Analysis was performed on neonatal length and weight data obtained from the Lithuanian Medical Birth Register from 1995 to 2015 (618,235 newborns of 24-42 gestational weeks). Their distributions by gestation and sex were estimated using generalized additive models for location, scale, and shape (GAMLSS), and the results were compared with the INTERGROWTH-21st (IG-21) standard to evaluate the prevalence of SGA/LGA (10th/90th centile) at different gestational ages.

Results

The difference in median length at term between the local reference and IG-21 was 3 cm-4 cm, while median weight at term differed by 200 g. The Lithuanian median weight at term was higher than in IG-21 by a full centile channel width, while the median length at term was higher by two channel widths. Based on the regional reference, the prevalence rates of SGA/LGA were 9.7%/10.1% for boys and 10.1%/9.9% for girls, close to the nominal 10%. Conversely, based on IG-21, the prevalence of SGA in boys/girls was less than half (4.1%/4.4%), while the prevalence of LGA was double (20.7%/19.1%).

Discussion

Regional population-based neonatal references represent Lithuanian neonatal weight and length much more accurately than the global standard IG-21 which provides the prevalence rates for SGA/LGA that differ from the true values by a factor of two.

Update Reference Charts: Fetal Biometry between the 15th and 42nd Week of Gestation

OBJECTIVES

This study was designed to establish new reference charts for BPD (biparietal diameter), OFD (occipitofrontal diameter), HC (head circumference), CM (cisterna magna), TCD (transverse cerebellar diameter), PCV (posterior cerebral ventricle), AC (abdominal circumference), FL (femur length), and HL (humerus length) and extend known charts to 42 weeks of gestation. These new charts were compared to studies carried out by Snijders and Nicolaides, the INTERGROWTH 21st Project, and the WHO Fetal Growth Charts.

METHODS

In this retrospective cross-sectional single-center study of 12,972 low-risk pregnancies, biometric data between the 15th and 42nd weeks of gestation were evaluated. Only one examination per pregnancy was selected for statistical analysis. Descriptive analysis for the 5th, 50th, and 95th quantile was performed for each parameter as listed above. Regression models were used to fit the mean and the SD at each gestational age.

RESULTS

Initially the reference curves for BPD, OFD, HC, AC, FL, and HL show a linear increase, which changes into a cubic increase towards the end of pregnancy. The results of this study show statistically noticeable differences from the percentile curves of the studies listed above.

CONCLUSIONS

The percentile curves in this study differ from the commonly used ones. The presented standard curves can be used as a reference in prenatal diagnostics.

The choice of reference chart affects the strength of the association between malaria in pregnancy and small for gestational age: an individual participant data meta-analysis comparing the Intergrowth-21 with a Tanzanian birthweight chart

BACKGROUND

The prevalence of small for gestational age (SGA) may vary depending on the chosen weight-for-gestational-age reference chart. An individual participant data meta-analysis was conducted to assess the implications of using a local reference (STOPPAM) instead of a universal reference (Intergrowth-21) on the association between malaria in pregnancy and SGA.

METHODS

Individual participant data of 6,236 newborns were pooled from seven conveniently identified studies conducted in Tanzania and Malawi from 2003-2018 with data on malaria in pregnancy, birthweight, and ultrasound estimated gestational age. Mixed-effects regression models were used to compare the association between malaria in pregnancy and SGA when using the STOPPAM and the Intergrowth-21 references, respectively.

RESULTS

The 10th percentile for birthweights-for-gestational age was lower for STOPPAM than for Intergrowth-21, leading to a prevalence of SGA_STOPPAM of 14.2% and SGA_IG21 of 18.0%, p < 0.001. The association between malaria in pregnancy and SGA was stronger for STOPPAM (adjusted odds ratio (aOR) 1.30 [1.09-1.56], p < 0.01) than for Intergrowth-21 (aOR 1.19 [1.00-1.40], p = 0.04), particularly among paucigravidae (SGA_STOPPAM aOR 1.36 [1.09-1.71], p < 0.01 vs SGA_IG21 aOR 1.21 [0.97-1.50], p = 0.08).

CONCLUSIONS

The prevalence of SGA may be overestimated and the impact of malaria in pregnancy underestimated when using Intergrowth-21. Comparing local reference charts to global references when assessing and interpreting the impact of malaria in pregnancy may be appropriate.

Which fetal growth charts should be used? A retrospective observational study in China

BACKGROUND

The fetal growth charts in widest use in China were published by Hadlock >35 years ago and were established on data from several hundred of American pregnant women. After that, >100 fetal growth charts were published around the world. We attempted to assess the impact of applying the long-standing Hadlock charts and other charts in a Chinese population and to compare their ability to predict newborn small for gestational age (SGA).

METHODS

For this retrospective observational study, we reviewed all pregnant women ( n  = 106,455) who booked prenatal care with ultrasound measurements for fetal biometry at the Shenzhen Maternity and Child Healthcare Hospital between 2012 and 2019. A fractional polynomial regression model was applied to generate Shenzhen fetal growth chart ranges for head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL). The differences between Shenzhen charts and published charts were quantified by calculating the Z -score. The impact of applying these published charts was quantified by calculating the proportions of fetuses with biometric measurements below the 3rd centile of these charts. The sensitivity and area under the receiver operating characteristic curves of published charts to predict neonatal SGA (birthweight <10th centile) were assessed.

RESULTS

Following selection, 169,980 scans of fetal biometry contributed by 41,032 pregnancies with reliable gestational age were analyzed. When using Hadlock references (<3rd centile), the proportions of small heads and short femurs were as high as 8.9% and 6.6% in late gestation, respectively. The INTERGROWTH-21st standards matched those of our observed curves better than other charts, in particular for fat-free biometry (HC and FL). When using AC<10th centile, all of these references were poor at predicting neonatal SGA.

CONCLUSIONS

Applying long-standing Hadlock references could misclassify a large proportion of fetuses as SGA. INTERGROWTH-21st standard appears to be a safe option in China. For fat-based biometry, AC, a reference based on the Chinese population is needed. In addition, when applying published charts, particular care should be taken due to the discrepancy of measurement methods.

Neonatal head circumference by gestation reflects adaptation to maternal body size: comparison of different standards

Neonatal head circumference (HC) not only represents the brain size of Homo sapiens, but is also an important health risk indicator. Addressing a lack of comparative studies on head size and its variability in term and preterm neonates from different populations, we aimed to examine neonatal HC by gestation according to a regional reference and a global standard. Retrospective analysis of data on neonatal HC obtained from the Lithuanian Medical Birth Register from 2001 to 2015 (423 999 newborns of 24–42 gestational weeks). The varying distribution by gestation and sex was estimated using GAMLSS, and the results were compared with the INTERGROWTH-21st standard. Mean HC increased with gestation in both sexes, while its fractional variability fell. The 3rd percentile matched that for INTERGROWTH-21st at all gestations, while the 50th and 97th percentiles were similar up to 27 weeks, but a full channel width higher than INTERGROWTH-21st at term. INTERGROWTH-21st facilitates the evaluation of neonatal HC in early gestations, while in later gestations, the specific features of neonatal HC of a particular population tend to be more precisely represented by regional references.

Assessing fetal growth in Africa: Application of the international WHO and INTERGROWTH-21st standards in a Beninese pregnancy cohort

BACKGROUND

Fetal growth restriction is a major complication of pregnancy and is associated with stillbirth, infant death and child morbidity. Ultrasound monitoring of pregnancy is becoming more common in Africa for fetal growth monitoring in clinical care and research, but many countries have no national growth charts. We evaluated the new international fetal growth standards from INTERGROWTH-21st and WHO in a cohort from southern Benin.

METHODS

Repeated ultrasound and clinical data were collected in women from the preconceptional RECIPAL cohort (241 women with singleton pregnancies, 964 ultrasounds). We modelled fetal biometric parameters including abdominal circumference (AC) and estimated fetal weight (EFW) and compared centiles to INTERGROWTH-21st and WHO standards, using the Bland and Altman method to assess agreement. For EFW, we used INTERGROWTH-21st standards based on their EFW formula (IG21st) as well as a recent update using Hadlock's EFW formula (IG21hl). Proportions of fetuses with measurements under the 10th percentile were compared.

RESULTS

Maternal malaria and anaemia prevalence was 43% and 69% respectively and 11% of women were primigravid. Overall, the centiles in the RECIPAL cohort were higher than that of INTERGROWTH-21st and closer to that of WHO. Consequently, the proportion of fetuses under 10th percentile thresholds was systematically lower when applying IG21st compared to WHO standards. At 27-31 weeks and 33-38 weeks, respectively, 7.4% and 5.6% of fetuses had EFW <10th percentile using IG21hl standards versus 10.7% and 11.6% using WHO standards.

CONCLUSION

Despite high anemia and malaria prevalence in the cohort, IG21st and WHO standards did not identify higher than expected proportions of fetuses under the 10th percentiles of ultrasound parameters or EFW. The proportions of fetuses under the 10th percentile threshold for IG21st charts were particularly low, raising questions about its use to identify growth-restricted fetuses in Africa.

Swedish intrauterine growth reference ranges for estimated fetal weight

Fetal growth restriction is a strong risk factor for perinatal morbidity and mortality. Reliable standards are indispensable, both to assess fetal growth and to evaluate birthweight and early postnatal growth in infants born preterm. The aim of this study was to create updated Swedish reference ranges for estimated fetal weight (EFW) from gestational week 12-42. This prospective longitudinal multicentre study included 583 women without known conditions causing aberrant fetal growth. Each woman was assigned a randomly selected protocol of five ultrasound scans from gestational week 12 + 3 to 41 + 6. Hadlock's 3rd formula was used to estimate fetal weight. A two-level hierarchical regression model was employed to calculate the expected median and variance, expressed in standard deviations and percentiles, for EFW. EFW was higher for males than females. The reference ranges were compared with the presently used Swedish, and international reference ranges. Our reference ranges had higher EFW than the presently used Swedish reference ranges from gestational week 33, and higher median, 2.5th and 97.5th percentiles from gestational week 24 compared with INTERGROWTH-21st. The new reference ranges can be used both for assessment of intrauterine fetal weight and growth, and early postnatal growth in children born preterm.

Should Fetal Growth Charts Be References or Standards?

BACKGROUND

Fetal growth standards (prescriptive charts derived from low-risk pregnancies) are theoretically better tools to monitor fetal growth than conventional references. We examined how modifying chart inclusion criteria influenced the resulting curves.

METHODS

We summarized estimated fetal weight (EFW) distributions from a hospital's routine 32-week ultrasound in all nonanomalous singleton fetuses (reference) and in those without maternal-fetal conditions affecting fetal growth (standard). We calculated EFWs for the 3rd, 5th, 10th, and 50th percentiles, and the proportion of fetuses each chart classified as small for gestational age.

RESULTS

Of 2309 fetuses in our reference, 690 (30%) met the standard's inclusion criteria. There were no meaningful differences between the EFW distributions of the reference and standard curves (50th percentile: 1989 g reference vs. 1968 g standard; 10th percentile: 1711 g reference vs. 1710 g standard), or the proportion of small for gestational age fetuses (both 9.9%).

CONCLUSIONS

In our study, there was little practical difference between a fetal growth reference and standard for detecting small infants.

Swedish intrauterine growth reference ranges of biometric measurements of fetal head, abdomen and femur

Ultrasonic assessment of fetal growth is an important part of obstetric care to prevent adverse pregnancy outcome. However, lack of reliable reference ranges is a major barrier for accurate interpretation of the examinations. The aim of this study was to create updated Swedish national reference ranges for intrauterine size and growth of the fetal head, abdomen and femur from gestational week 12 to 42. This prospective longitudinal multicentre study included 583 healthy pregnant women with low risk of aberrant fetal growth. Each woman was examined up to five times with ultrasound from gestational week 12 + 3 to 41 + 6. The assessed intrauterine fetal biometric measurements were biparietal diameter (outer–inner), head circumference, mean abdominal diameter, abdominal circumference and femur length. A two-level hierarchical regression model was employed to account for the individual measurements of the fetus and the number of repeated visits for measurements while accounting for the random effect of the identified parameterization of gestational age. The expected median and variance, expressed in both standard deviations and percentiles, for each individual biometric measurement was calculated. The presented national reference ranges can be used for assessment of intrauterine size and growth of the fetal head, abdomen and femur in the second and third trimester of pregnancy.

Current use and performance of the different fetal growth charts in the Italian population

OBJECTIVES

The choice of growth charts impacts on screening, diagnosis and clinical management of fetal growth abnormalities. The objectives of the study were to evaluate: 1) the clinical practice at a national level among tertiary referral centers in the use of fetal biometric growth charts; and 2) the impact on fetal growth screening of existing national and international growth charts.

STUDY DESIGN

A questionnaire was sent to 14 Italian tertiary referral centers to explore biometric reference growth charts used in clinical practice. National and international (Intergrowth-21st and World Health Organization) fetal growth charts were tested on a large national cohort of low risk women with singleton uneventful pregnancy derived from a retrospective cross-sectional multicenter study (21 centers). The percentage of fetuses with biometric measurements below and above the 10th and 90th percentile for each biometric parameter and gestational week were calculated for each growth chart. The percentile curves of the study population were calculated by non-linear quantile regressions.

RESULTS

Twelve Italian centers (86 %) answered to the questionnaire showing a wide discrepancy in the use of growth charts for fetal biometry. The cohort included 7347 pregnant women. By applying Intergrowth-21st growth charts the percentage of fetuses with head circumference, abdominal circumference and femur length below the 10th centile was 3.9 %, 3.6 % and 2.3 %, and above the 90th centile 29.9 %, 32.5 % and 46 %, respectively. The percentages for the World Health Organization growth charts for head and abdominal circumferences and femur length were: below the 10th centile 6.3 %, 7.2 % and 5.3 %, and above 90th centile 22.8 %, 21.3 % and 31.9 %, respectively.

CONCLUSIONS

The wide discrepancy in clinical use of fetal growth charts in Italian centers warrants the adoption of an uniform set of charts. Our data suggest that immediate application into clinical practice of international growth charts might result into an under-diagnosis of small for gestational age fetuses and, especially, in an over-diagnosis of large for gestational age fetuses with major consequences for clinical practice. On these grounds, there is an urgent need for a nationwide study for the prospective evaluation of international growth charts and, if needed, the construction and adoption of methodologically robust national growth charts.

Are selection criteria for healthy pregnancies responsible for the gap between fetal growth in the French national Elfe birth cohort and the Intergrowth-21st fetal growth standards?

BACKGROUND

The Intergrowth-21st (IG) project proposed prescriptive fetal growth standards for global use based on ultrasound measurements from a multicounty study of low-risk pregnancies selected using strict criteria. We examined whether the IG standards are appropriate for fetal growth monitoring in France and whether potential differences could be due to IG criteria for "healthy" pregnancies.

METHOD

We analysed data on femur length and abdominal circumference at the second and/or the third recommended ultrasound examination from 14 607 singleton pregnancies from the Elfe national birth cohort. We compared concordance of centile thresholds using the IG standards and current French references and used restricted cubic splines to plot z-scores by gestational age. A "healthy pregnancy" sub-sample was created based on maternal and pregnancy selection criteria, as specified by IG.

RESULTS

Mean gestational age-specific z-scores for femur length and abdominal circumference using French references fluctuated around 0 (-0.2 to 0.1), while those based on IG standards were higher (0.3-0.8). Using IG standards, 2.5% and 5.2% of fetuses at the third ultrasound were <10th centile for femur length and abdominal circumference, respectively, and 31.5% and 16.7% were >90th. Only 34% of pregnancies fulfilled IG low-risk criteria, but sub-analyses yielded very similar results.

CONCLUSION

Intergrowth standards differed from fetal biometric measures in France, including among low-risk pregnancies selected to replicate IG's healthy pregnancy sample. These results challenge the project's assumption that careful constitution of a low-risk population makes it possible to describe normative fetal growth across populations.