Anaemia in the first trimester and poor physiological plasma expansion during pregnancy negatively impact foetal weight and newborn anthropometrics: An observational cohort study in Tanzania

OBJECTIVES

Anaemia during pregnancy is a major health challenge affecting pregnancy outcome worldwide. The objectives of this study were to investigate the impact of severe-moderate anaemia in the first trimester, as well as changes in haemoglobin during pregnancy among non-anaemic women, on foetal weight, placental blood flow and newborn anthropometrics.

METHODS

In a prospective cohort study, 346 women residing in rural Tanzania were followed throughout pregnancy with serial ultrasound and newborn anthropometrics assessed within 24 h of delivery. Associations between placental blood flow, foetal weight and newborn anthropometrics with either first trimester severe-moderate anaemia (haemoglobin≤9.5 g/dL) or changes in haemoglobin from the first to the third trimester among non-anaemic women, were assessed by mixed model regression and multiple linear regression, adjusting for maternal and foetal co-variables. Foetal weights and birthweight were converted to z-scores using a population based sex-specific weight reference.

RESULTS

Severe-moderate anaemia in the first trimester was associated with significantly reduced foetal weight z-scores (adjusted mean difference (aMD) -0.44 (95% CI -0.81, -0.07)) and newborn anthropometric indices (birth weight z-score aMD -0.55 (-0.9, -0.13), abdominal circumference aMD -11 mm (95% CI -20, -3)). There were no association between first trimester severe-moderate anaemia and placental blood flow. Among women who were non-anaemic in the first trimester, women with the least reduction in haemoglobin (Δ ≥ -0.3 g/dL) delivered significantly smaller newborns (birthweight z-score aMD -0.55 (-0.91, -0.20), abdominal circumference aMD -10 mm (95% CI -17, -3), compared to women with the greatest reduction (Δ haemoglobin ≤ -1.4 g/dL)).

CONCLUSIONS

Severe-moderate anaemia in early pregnancy was associated with smaller newborn anthropometrics which was reflected in smaller mean foetal weights in the second and third trimester. Furthermore, among women who were non-anaemic in the first trimester, there was an association between smaller newborn anthropometrics and limited haemoglobin decrease during pregnancy, possibly reflecting insufficient plasma expansion.

Accuracy of ultrasound in the estimation of customised birth weight in a public hospital service

INTRODUCTION

Studies have shown that ultrasound estimated foetal weight (EFW) in small for gestational age (SGA) babies tends to be less-accurate when compared to appropriate (AGA) and large (LGA) for gestational age babies. We aimed to analyse the accuracy of ultrasound EFW overall, and by customised birth weight centile category (severe SGA, SGA, AGA, LGA). Also, the accuracy of estimating the centile category using calculated customised EFW centiles.

METHODS

We performed a retrospective study of pregnant women between 20-43 weeks gestation who underwent ultrasound within 7 days of delivery at a large tertiary maternity unit between January 2018 and December 2020. Stillbirths, major foetal anomalies and multiple pregnancies were excluded. The EFW and birth weight were compared, and an accurate estimate defined as ≤15% difference. The customised EFW and birth weight centiles were calculated and used to analyse the accuracy of category prediction.

RESULTS

Of 2061 foetuses included, 92% (n = 1902) were born weighing within 15% of their EFW. Accuracy was not affected by maternal BMI, ethnicity, parity or gestation. 87% of SGA babies were within 15% of their EFW. Ultrasound sensitivity for SGA was 51% (95% CI: 46-55%). The specificity and positive predictive values were 97% (95% CI: 96-98%) and 87% (95% CI: 82-90%) respectively.

CONCLUSION

The accuracy of Ultrasound EFW overall is good, however, is reduced in SGA babies whose EFW and birth weight centile categories tended to be overestimated. The high specificity for SGA supports monitoring with a lowered threshold to intervene in pregnancies identified by ultrasound as SGA.

Validity of two-dimensional ultrasound for determining extreme foetal weights to term

The aim of this study was to assess the validity of ultrasound carried out within seven days prior to birth at term for the calculation of full term estimated foetal weight (EFW) in order to diagnose extreme foetal weight, performed using a single-center retrospective cohort study of 2500 pregnant women. Ultrasound calculations of EFW with a standard error of less than 10% showed an accuracy ratio of 75.1% for the total sample. This percentage was similar for appropriate for gestational age (78.6%) and normal foetal weights (77.5%) but decreased significantly (p < .01) in the case of extreme foetal weights. The simple error increased in both the high and low EFWs, taking on positive values for the low weights and negative values for the high weights. As for the percentage error values, there was a tendency for positive errors for low weights and negative errors for high weights; this led to a tendency to overestimate low foetal weights and underestimate high foetal weights.IMPACT STATEMENTWhat is already known on this subject? Two-dimensional ultrasound is currently the principal tool used in obstetrics to evaluate foetal growth, mainly through the calculation of EFW. Foetal weight represents an important prognostic factor in perinatal results, with a greater risk of adverse effects in cases of extreme foetal weights. In this sense, there are few studies that assess the validity of EFW calculations focussing on extreme foetal weights to term.What do the results of this study add? The ultrasound estimates of EFW with an error lower than 10% in the seven days prior to birth showed an accuracy ratio of 75.1% for the total sample. This percentage was similar to appropriate for gestational age weights (78.6%) and of normal weights (77.5%), but decreased significantly (p < .01) in the case of extreme foetal weights: small for gestational age (52.1%), large for gestational age (68.2%), microsomia (49.1%), and macrosomia (61%). Likewise, we found high specificity and low sensitivity for ultrasound diagnosis of extreme foetal weights.What are the implications of these findings for clinical practice and/or future research? The validity of ultrasound EFW is influenced by extreme foetal weights, with a tendency to overestimate low weights and underestimate high weights, which represents a clinically important finding.

Are ultrasound foetal circumference measurement methods interchangeable?

A variety of methods is available for the ultrasound measurement of foetal circumferences; ellipse fitting and derived measurements are often used interchangeably based on an assumption of equivalence, despite evidence that results may differ. The aim of this study was to investigate the differences between ellipse fitting and derived circumferences in clinical practice. Head and abdominal circumferences originally measured using ellipse fitting were retrospectively derived from anterior-posterior and transverse diameters using a widely used formula. Where the necessary measurements were available, foetal weight was estimated. Differences between ellipse fitted and derived measurements were compared using Bland-Altman plots. Images from 65 patients (gestational age 20 to 40 weeks) were collected; four head circumference and five abdominal circumference images were excluded due to poor image quality. Data were available for estimated foetal weight calculation for 48 patients. There were small systematic differences between ellipse fitted and derived measurements. Random differences varied between 20 week scans, early growth scans and later growth scans, so were analysed in these three groups. The 95% confidence intervals were ±6 mm (±3%), ±7 mm (±2%) and ±20 mm (±6%) for head circumference at 20 weeks, earlier growth scans and later scans, respectively; the 95% confidence intervals for abdominal circumference were ±7 mm (±5%), ±11 mm (±5%) and ±17 mm (±6%) and for estimated foetal weight were ±23 g (±6%), ±69 g (±5%) and ±311 g (±12%). Foetal circumference measurement methods are not interchangeable. The derived method should be used where size, growth and estimated foetal weight charts are based on this method.

Maternal rates of lipolysis and glucose production in late pregnancy are independently related to foetal weight

OBJECTIVE

Associations between maternal glucose levels and increased foetal growth are well established, and independent relationships with maternal weight, weight gain and insulin resistance are also observed. The relative roles of lipolysis and glucose production in the determination of these observations remain unclear.

DESIGN

We examined, through detailed physiological studies, the relationship between maternal late gestational energy substrate production (glucose and glycerol), maternal weight and weight gain, and estimated foetal size in the third trimester.

PATIENTS

Twenty-one nulliparous pregnant women, without gestational diabetes (GDM) assessed at 28 weeks with oral glucose tolerance test, were recruited.

MEASUREMENTS

Rates of hepatic glucose production (GPR) and rates of glycerol production (reflecting lipolysis) using [¹³ C₆ ]-glucose and [² H₅ ]-glycerol were measured at 34-36 weeks of gestation. Respiratory quotient was assessed by indirect calorimetry and body composition by measurements of total body water (TBW; H₂¹⁸ O) and body density (BODPOD). Foetal weight was estimated from ultrasound measures of biparietal diameter, femoral length and abdominal circumference.

RESULTS

At 34-36 weeks, bivariate analyses showed that GPR and lipolysis correlated with estimated foetal weight (r=.71 and .72, respectively) as well as with maternal weight, fat mass and fat-free mass, but not maternal weight gain. In multivariate analyses, rates of both glucose production (r=.42) and lipolysis (r=.47) were independently associated with foetal size explaining 63% of the variance.

CONCLUSIONS

Both maternal rates of lipolysis and hepatic glucose production in late gestation are strongly related to estimated foetal weight.

Arginine for gestating sows and foetal development: A systematic review

The use of functional amino acids during pregnancy has been linked to improved reproduction in mammals. In this context, arginine is a precursor in the synthesis of numerous molecules, such as nitric oxide and polyamines, which play an important role during reproduction. However, contradictory studies are found in the literature, particularly regarding the amount of supplementation and the period of pregnancy in which it is used. The objective of this study was to evaluate the effects of dietary arginine supplementation for pregnant sows on foetal development via a systematic review. The search for papers was performed during the month of December 2015, in the databases ISI Web of Science, Science Direct, Scopus, and SciELO. From a total of 5675 returned studies, only 13 papers were selected after applying selection criteria. Most (47%) of the studies that evaluated the effects of dietary arginine supplementation on foetal development in pigs used 1% arginine. Supplementation was initiated in the first third of pregnancy in 47% of tests, including in both primiparous and multiparous sows. These studies showed positive results for embryo survival and foetal development, evidenced by the increase in placental weight and the number and weight of piglets born alive. Of all evaluated studies, 53% showed benefits on foetal development. It is concluded that supplementing dietary arginine in gestating sows can benefit embryo survival and foetal development. However, to establish a supplementation plan with this amino acid, aspects related to the period of pregnancy, supplementation levels, and source of arginine must be well defined.

Changes in placental angiogenesis and their correlation with foetal intrauterine restriction

TYPE OF STUDY

Summary review.

SETTING

Department of Gynaecology and Obstetrics, 1st Faculty of Medicine, Charles University and Hospital Na Bulovce, Prague; Department of Physiology, Faculty of Science, Charles University, Prague; Department of Children and Adolescent Medicine, 1st Faculty of Medicine, Charles University in Prague and General Teaching Hospital, Prague.

INTRODUCTION

Intrauterine growth restriction (IUGR) is one of the most common problems in obstetrics. Its incidence is ranging between 3-10%, according to the type of study population and chosen criteria. The cutoff value mainly used for defining the IUGR is weight below the 10th percentile for gestational age. The minority of authors defines the cutoff value under the 5th or 3rd percentile. Any pathological interference with normal vascular development of placenta may have a critical impact on foetal growth and development. Ischaemia is the most common cause of IUGR in normally well-supplied placenta. IUGR is then a consequence of insufficient extension, branching, and dilatation of capillary loops during the formation of terminal villi.

METHODS

This paper is a review focused on up-to-date-known data concerning changes in placental angiogenesis and their impact on IUGR development.

CONCLUSION

The aim of this review is to summarize the knowledge concerning the mechanisms of development of the vascular supply to the placenta under physiological conditions and in conditions that result in IUGR.

Relationship between amniotic fluid index and ultrasound estimated fetal weight in healthy pregnant african women

Introduction:

Fetal weight (FW) estimation in late pregnancy is an important guide in obstetric care. Amniotic fluid protects the fetus against traumatic and infective insults. There possibly exists a relationship between FW and amniotic fluid index (AFI) that can be estimated by ultrasonography.

Materials and Methods:

Two hundred and fifty-eight low-risk pregnancies were prospectively studied by means of ultrasound over a 12-month period. FW was estimated using a combination of fetal parameters; bi-parietal diameter, fetal trunk cross sectional area, and femur length. AFI was assessed using the 4-quadrant method. Spearman's correlation was used to test possible relationship between amniotic fluid indices and estimated FW pairs. The level of statistical significance was set at P ≤ 0.05.

Results:

The mean AF1 and estimated fetal weight (EFW) pairs were as follows: at 27-29 weeks the values were 172.1 mm and 1,250.2 g; at 30-32 weeks AF1 and EFW values were 170.3 mm and 1,648.0 g; at 33-35 weeks values were 162.3 mm and 2,273.5 g; at 36-38 weeks values were 144.09 mm and 2,906.1 g; at 39-40 weeks AF1 and EFW values were 125.0 mm and 3,222.6 g. Overall, there was no statistically significant relationship between AFI and EFW (P > 0.05; r = 0.241).

Conclusion:

While FW calculations and amniotic index showed variations in value in late pregnancy, there does not appear to be a linear relationship between ultrasound estimate of FW and amniotic index. The implication of this is that fetal size need not be taken into cognizance when alterations in amniotic fluid values are noted.

Ultrasonographic biometry: Biparietal Diameter of Nigerian foetuses

BACKGROUND: Foetal biparietal diameter has been studied previously in Nigerian foetuses but populations have been too small to make categorical conclusions regarding the reference values/data. MATERIALS AND METHODS: In a cross sectional study, the foetal biparietal diameter (BPD) of 13,740 foetuses in Jos were measured with grey ultrasound machine in 13,740 Nigerian women during normal pregnancy and the mean BPD values for each week of pregnancy between 12 and 42 weeks were determined. RESULTS: The mean biparietal diameter value was 29.4mm at 14 weeks, 49.4mm at 20 weeks, 78.4mm at 30 weeks, 91.5 at 37 weeks and 95.6mm at 40 weeks. There was a positive relationship between gestational age and biparietal diameter with correlation coefficient of R(2) = 0.9996 (P < 0.001), and with fetal weight. The increase in BPD with increasing age in the study population showed a curve similar to that of Europeans. CONCLUSIONS: Ultrasonographic measurement of biparietal diameter in Nigerian fetuses showed a linear correlation exists between BPD and gestational age, as well as BPD and foetal weight in normal foetuses.

Clinical versus sonographic estimation of foetal weight in southwest Nigeria

A prospective study was conducted at Obafemi Awolowo University Teaching Hospital Complex, Ile-Ife, Nigeria, between 3 January and 31May 2004, to compare the accuracy of clinical and ultrasonographic estimation of foetal weight at term. One hundred pregnant women who fulfilled the inclusion criteria had their foetal weight estimated independently using clinical and ultrasonographic methods. Accuracy was determined by percentage error, absolute percentage error, and proportion of estimates within 10% of actual birth-weight (birth-weight of +10%). Statistical analysis was done using the paired t-test, the Wilcoxon signed-rank test, and the chi-square test. The study sample had an actual average birth-weight of 3,255+622 (range 2,150-4,950) g. Overall, the clinical method overestimated birth-weight, while ultrasound underestimated it. The mean absolute percentage error of the clinical method was smaller than that of the sonographic method, and the number of estimates within 10% of actual birth-weight for the clinical method (70%) was greater than for the sonographic method (68%); the difference was not statistically significant. In the low birth-weight (<2,500 g) group, the mean errors of sonographic estimates were significantly smaller, and significantly more sonographic estimates (66.7%) were within 10% of actual birth-weight than those of the clinical method (41.7%). No statistically significant difference was observed in all the measures of accuracy for the normal birth-weight range of 2,500-<4,000 g and in the macrosonic group (> or =4,000 g), except that, while the ultrasonographic method underestimated birth-weight, the clinical method overestimated it. Clinical estimation of birth-weight is as accurate as routine ultrasonographic estimation, except in low-birth-weight babies. Therefore, when the clinical method suggests weight smaller than 2,500 g, subsequent sonographic estimation is recommended to yield a better prediction and to further evaluate foetal well-being.