Charts to assess fetal wellbeing

Sex differences in fetal growth and immediate birth outcomes in a low-risk Caucasian population

Background

According to the WHO Multicentre Growth Reference Study Group recommendations, boys and girls have different growth trajectories after birth. Our aim was to develop gender-specific fetal growth curves in a low-risk population and to compare immediate birth outcomes.

Methods

First, second, and third trimester fetal ultrasound examinations were conducted between 2002 and 2012. The data was selected using the following criteria: routine examinations in uncomplicated singleton pregnancies, Caucasian ethnicity, and confirmation of gestational age by a crown-rump length (CRL) measurement in the first trimester. Generalized Additive Model for Location, Scale and Shape (GAMLSS) was used to align the time frames of the longitudinal fetal measurements, corresponding with the methods of the postnatal growth curves of the WHO MGRS Group.

Results

A total of 27,680 complete scans were selected from the astraia© ultrasound database representing 12,368 pregnancies. Gender-specific fetal growth curves for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were derived. The HC and BPD were significantly larger in boys compared to girls from 20 weeks of gestation onwards (p < 0.001) equating to a 3-day difference at 20–24 weeks. Boys were significantly heavier, longer, and had greater head circumference than girls (p < 0.001) at birth. The Apgar score at 1 min (p = 0.01) and arterial cord pH (p < 0.001) were lower in boys.

Conclusions

These longitudinal fetal growth curves for the first time allow integration with neonatal and pediatric WHO gender-specific growth curves. Boys exceed head growth halfway of the pregnancy, and immediate birth outcomes are worse in boys than girls. Gender difference in intrauterine growth is sufficiently distinct to have a clinically important effect on fetal weight estimation but also on the second trimester dating. Therefore, these differences might already play a role in early fetal or immediate neonatal management.

Electronic supplementary material

The online version of this article (10.1186/s13293-019-0261-7) contains supplementary material, which is available to authorized users.

Reference ranges for Doppler indices of umbilical and fetal middle cerebral arteries and cerebroplacental ratio: systematic review

OBJECTIVE

To assess studies reporting reference ranges for umbilical artery (UA) and fetal middle cerebral artery (MCA) Doppler indices and cerebroplacental ratio (CPR), using a set of predefined methodological quality criteria for study design, statistical analysis and reporting methods.

METHODS

This was a systematic review of observational studies in which the primary aim was to create reference ranges for UA and MCA Doppler indices and CPR in fetuses of singleton gestations. A search for relevant articles was performed in MEDLINE, EMBASE, CINAHL, Web of Science (from inception to 31 December 2016) and references of the retrieved articles. Two authors independently selected studies, assessed the risk of bias and extracted the data. Studies were scored against a predefined set of independently agreed methodological criteria and an overall quality score was assigned to each study. Linear multiple regression analysis assessing the association between quality scores and study characteristics was performed.

RESULTS

Thirty-eight studies met the inclusion criteria. The highest potential for bias was noted in the following fields: 'ultrasound quality control measures', in which only two studies demonstrated a comprehensive quality-control strategy; 'number of measurements taken for each Doppler variable', which was apparent in only three studies; 'sonographer experience', in which no study on CPR reported clearly the experience or training of the sonographers, while only three studies on UA Doppler and four on MCA Doppler did; and 'blinding of measurements', in which only one study, on UA Doppler, reported that sonographers were blinded to the measurement recorded during the examination. Sample size estimations were present in only seven studies. No predictors of quality were found on multiple regression analysis. Reference ranges varied significantly with important clinical implications for what is considered normal or abnormal, even when restricting the analysis to the highest scoring studies.

CONCLUSIONS

There is considerable methodological heterogeneity in studies reporting reference ranges for UA and MCA Doppler indices and CPR, and the resulting references have important implications for clinical practice. There is a need for the standardization of methodologies for Doppler velocimetry and for the development of reference standards, which can be correctly interpreted and applied in clinical practice. We propose a set of recommendations for this purpose. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Systematic review of methodology used in ultrasound studies aimed at creating charts of fetal size

BACKGROUND

Reliable ultrasound charts are necessary for the prenatal assessment of fetal size, yet there is a wide variation of methodologies for the creation of such charts.

OBJECTIVE

To evaluate the methodological quality of studies of fetal biometry using a set of predefined quality criteria of study design, statistical analysis and reporting methods.

SEARCH STRATEGY

Electronic searches in MEDLINE, EMBASE and CINAHL, and references of retrieved articles.

SELECTION CRITERIA

Observational studies whose primary aim was to create ultrasound size charts for bi-parietal diameter, head circumference, abdominal circumference and femur length in fetuses from singleton pregnancies.

DATA COLLECTION AND ANALYSIS

Studies were scored against a predefined set of independently agreed methodological criteria and an overall quality score was given to each study. Multiple regression analysis between quality scores and study characteristics was performed.

MAIN RESULTS

Eighty-three studies met the inclusion criteria. The highest potential for bias was noted in the following fields: 'Inclusion/exclusion criteria', as none of the studies defined a rigorous set of antenatal or fetal conditions which should be excluded from analysis; 'Ultrasound quality control measures', as no study demonstrated a comprehensive quality assurance strategy; and 'Sample size calculation', which was apparent in six studies only. On multiple regression analysis, there was a positive correlation between quality scores and year of publication: quality has improved with time, yet considerable heterogeneity in study methodology is still observed today.

CONCLUSIONS

There is considerable methodological heterogeneity in studies of fetal biometry. Standardisation of methodologies is necessary in order to make correct interpretations and comparisons between different charts. A checklist of recommended methodologies is proposed.

Fetal myocardial tissue Doppler indices before birth physiologically change in proportion to body size adjusted for gestational age in low-risk term pregnancies

BACKGROUND

Few studies have investigated the relationship between myocardial tissue Doppler parameters and fetal size adjusted for gestational age and its trend has been controversial.

AIMS

To investigate fetal cardiac function before birth using tissue Doppler imaging (TDI: indicated by the prime symbol (')) in low-risk term pregnancies by comparing the TDI parameters with gestational age-specific birth weight percentiles and z scores.

STUDY DESIGN AND MEASUREMENTS

Interventricular septum, left and right ventricular myocardial peak early diastolic (E'), late diastolic (A') and systolic (S') velocities, E'/A' ratios, myocardial performance index (MPI') and umbilical artery pulsatility index were measured within three days before birth in 76 low-risk term pregnancies, including appropriate for gestational age (AGA, n=50), small for gestational age (SGA, n=10), and large for gestational age (LGA, n=16) subjects.

RESULTS

Myocardial peak velocities showed higher in the LGA and lower in the SGA compared with the AGA group, and All S' positively correlated with birth weight (r=0.51-0.57). All z scores of S' demonstrated a positive correlation with birth weight z score (Spearman r=0.45-0.53). MPI' was significantly higher in the SGA and lower in the LGA compared with the AGA group. All MPI' negatively correlated with birth weight (r=-0.55 to -0.65). All z scores of MPI' showed a negative correlation with birth weight z score (Spearman r=-0.40 to -0.56).

CONCLUSIONS

Fetal myocardial peak velocities and MPI' physiologically changed in proportion to body size adjusted for gestational age in low-risk term pregnancies.

Development of Australian reference ranges for the left fetal modified myocardial performance index and the influence of caliper location on time interval measurement

OBJECTIVES

To construct gestational age-adjusted reference ranges of the left fetal modified myocardial performance index (Mod-MPI) in the Australian population and assess the influence of valve click caliper position on constituent time intervals and the Mod-MPI.

METHODS

This is a prospective longitudinal study of 117 normal singleton fetuses undergoing 318 ultrasound scans at 4-6 weekly intervals between 18 and 38 weeks of gestation. The isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT), and ejection time (ET) were measured at 3 different caliper positions in each fetus: beginning of the original valve clicks ('original'), beginning of the reflected valve clicks ('reflected'), and peak of valve clicks ('peak'). The Mod-MPI was calculated as (ICT + IRT)/ET.

RESULTS

The Mod-MPI increased throughout gestation with means ± SD of 0.42 ± 0.05 'reflected' and 'peak' versus 0.49 ± 0.03 'original' at 19 weeks, and means of 0.46 ± 0.05 'reflected and peak' versus 0.51 ± 0.08 'original' at 36 weeks. Throughout gestation, ICT remained fairly constant and IRT increased, while ET decreased with 'original' click and remained constant for 'reflected' and 'peak' clicks. A modest increase in Mod-MPI was seen with increasing fetal heart rate. Analysis of repeatability for the 3 methods showed the following ICCs: 'original', 0.797 (95% CI 0.762-0.829); 'reflected', 0.809 (95% CI 0.775-0.839), and 'peak', 0.799 (95% CI 0.764-0.831).

CONCLUSIONS

Detailed exploration of the morphology of mitral and aortic valve closure and opening clicks shows how selection of different phases of these clicks may significantly influence the Mod-MPI. We recommend that the peak of the valve clicks be standardized between research groups.