Problems of the Small-for-Dates Baby

Machine learning-based placental clusters and their associations with adverse pregnancy outcomes

BACKGROUND

Placental abnormalities have been described in clinical convenience samples, with predominately adverse outcomes. Few studies have described placental patterns in unselected samples.

OBJECTIVE

We aimed to investigate associations between co-occurring placental features and adverse pregnancy outcomes in a prospective cohort of singletons.

METHODS

Data were from the Safe Passage study (U.S. and South Africa, 2007-2015). Before 24 weeks' gestation, participants were randomly invited to donate placental tissue at delivery for blinded, standardised pathological examination. We used hierarchical clustering to construct statistically derived groups using 60 placental features. We estimated associations between the placental clusters and select adverse pregnancy outcomes, expressed as unadjusted and adjusted risk ratios (RRs) and robust 95% confidence intervals (CI).

RESULTS

We selected a 7-cluster model. After collapsing 2 clusters to form the reference group, we labelled the resulting 6 analytic clusters according to the overarching category of their most predominant feature(s): severe maternal vascular malperfusion (n = 117), fetal vascular malperfusion (n = 222), other vascular malperfusion (n = 516), inflammation 1 (n = 269), inflammation 2 (n = 175), and normal (n = 706). Risks for all outcomes were elevated in the severe maternal vascular malperfusion cluster. For instance, in unadjusted analyses, this cluster had 12 times the risk of stillbirth (RR 12.07, 95% CI 4.20, 34.68) and an almost doubling in the risk of preterm delivery (RR 1.93, 95% CI 1.27, 2.93) compared with the normal cluster. Small infant size was more common among the abnormal clusters, with the highest unadjusted RRs observed in the fetal vascular malperfusion cluster (small for gestational age birth RR 2.99, 95% CI 2.24, 3.98, head circumference <10th percentile RR 2.86, 95% CI 1.60, 5.12). Upon adjustment for known risk factors, most RRs attenuated but remained >1.

CONCLUSION

Our study adds to the growing body of epidemiologic research, finding adverse pregnancy outcomes may occur through etiologic mechanisms involving co-occurring placental abnormalities.

Trial of Labor After Cesarean of Small for Gestational Age Neonates Among Women with No Prior Vaginal Delivery - a Retrospective Study

To evaluate the characteristics and outcomes of women who had never delivered vaginally and underwent a trial of labor after cesarean (TOLAC) of small for gestational age (SGA) neonates, and to identify risk factors for unplanned repeat cesarean delivery. A retrospective cohort study from two tertiary medical centers. All women undergoing a TOLAC with no prior vaginal delivery, delivering a singleton SGA neonate at term between 2005 and 2020 were included. Factors associated with successful vaginal delivery were examined by a multivariable analysis. Of the 255 women who met the inclusion criteria and underwent TOLAC, 72.2% delivered vaginally. In a multivariable analysis, maternal height [adjusted odds ratio (aOR) (95% CI): 1.10 (1.02-1.19), p = 0.012] and epidural administration [aOR (95% CI): 2.78 (1.0-7.73), p = 0.050] were positively independently associated with TOLAC success, and hypertensive disorders were negatively independently associated with TOLAC success [aOR (95% CI): 0.52 (0.004-0.74), p = 0.029]. The success rate of TOLAC among women with no prior vaginal delivery, delivering a SGA neonate is relatively high. Maternal height, hypertensive disorders, and epidural administration are independent factors associated with TOLAC success. Epidural administration is a modifiable factor and should be taken in consideration during TOLAC management.

Monitoring fetal well-being in labor in late fetal growth restriction

Late-onset fetal growth restriction (FGR) accounts for approximately 70-80% of all cases of FGR secondary to uteroplacental insufficiency. It is associated with an increased incidence of adverse antepartum and perinatal events, which in most instances result from hypoxic insults either present at the onset of labor or supervening during labor as a result of uterine contractions. Labor represents a stressful event for the fetoplacental unit being uterine contractions associated with an up-to 60% reduction of the uteroplacental perfusion. Intrapartum fetal heart rate monitoring by means of cardiotocography (CTG) currently represents the mainstay for the identification of fetal hypoxia during labor and is recommended for the fetal surveillance during labor in the case of FGR or other conditions associated with an increased risk of intrapartum hypoxia. In this review we discuss the potential implications of an impaired placental function on the intrapartum adaptation to the hypoxic stress and the role of the CTG and alternative techniques for the intrapartum monitoring of the fetal wellbeing in the context of FGR secondary to uteroplacental insufficiency.

Fetal Growth Restriction: ACOG Practice Bulletin, Number 227

Fetal growth restriction, also known as intrauterine growth restriction, is a common complication of pregnancy that has been associated with a variety of adverse perinatal outcomes. There is a lack of consensus regarding terminology, etiology, and diagnostic criteria for fetal growth restriction, with uncertainty surrounding the optimal management and timing of delivery for the growth-restricted fetus. An additional challenge is the difficulty in differentiating between the fetus that is constitutionally small and fulfilling its growth potential and the small fetus that is not fulfilling its growth potential because of an underlying pathologic condition. The purpose of this document is to review the topic of fetal growth restriction with a focus on terminology, etiology, diagnostic and surveillance tools, and guidance for management and timing of delivery.

Sonographic growth curves versus neonatal birthweight growth curves for the identification of fetal growth restriction

OBJECTIVE

Fetal growth restriction is suspected when the estimated fetal weight is <10th percentile for gestational age. Using a regional sonographic estimated fetal weight growth curve to diagnose fetal growth restriction has no known benefits; however, the traditional approach of using birthweight curves is misleading, since a large proportion of preterm births arise from pathological pregnancies. Our aim was to compare the diagnostic accuracies of sonographic versus birthweight curves in diagnosing fetal growth restriction. Our secondary aim was to compare maternal, fetal and neonatal outcome based on these two approaches.

METHODS

Retrospective study based on computerized medical records. Included were women with a singleton pregnancy, that underwent fetal biometry between 24 and 36.6 weeks' gestation (January 2010-February 2016) and delivered in our center. Each pregnancy was assigned to one of three groups based on the earliest sonographic estimated fetal weight performed: G1-Appropriate for gestational age, G2-fetal growth restriction based on sonographic but not birthweight curves; or G3-fetal growth restriction based on birthweight growth curves. Demographics, obstetric characteristics, ultrasound data, and neonatal data were retrieved and compared between groups. Primary outcome: rate of small for gestational age neonates in each group. Secondary outcomes were various adverse maternal and neonatal outcomes.

RESULTS

Six thousand and five pregnancies met inclusion criteria. Of these 5386 (89.6%) were categorized as G1, 300 (5%) as G2 and 319 (5.3%) as G3. The rate of small for gestational age neonates differed significantly between groups: G1 9.2%, G2 39.7% and G3 70%. Multivariable logistic regression modeling reiterated these rates: the odds ratios for small for gestational age were 6.47 [95% CI 4.99-8.40] and 23.99 [95% CI 18.26-31.51] for G2 and G3 respectively. Prediction of small for gestational age based on sonographic EFW curves increased the sensitivity for detection of SGA from 26% to 41% with a slight decrease in specificity from 98% to 95%, and a decrease of the positive likelihood ratio from 18.4 to 7.7, however there was no significant change in the overall test accurcy; 88.5% to 87.1%. Secondary outcomes also differed between groups: G2 and G3 had similar rates of maternal and neonatal morbidities and most parameters were higher than G1. G2 and G3 showed lower mean gestational age at delivery (36.2 weeks and 35.9 weeks vs.37.8; p < .0001), and higher rates of preterm delivery (40% and 51.7% vs. 21.5%; p < .001), as well as higher rates of intrauterine fetal demise 3% in G2, 6.9% in G3 and 0.9% in G1, p < .0001.

CONCLUSION

Pregnancies that are currently managed as appropriate for gestational age based on birthweight curves, but classified as growth restricted when prenatal sonographic curves are used, are associated with higher rates of small for gestational age and poor perinatal outcomes, at rates comparable to pregnancies that are classified as growth restricted based on birthweight curves. Furthermore, applying sonographic curves increases the sensitivity for detection of small for gestational age neonates. Consequently, consideration should be given to the use of sonographic biometry curves for defining fetal growth restriction.

Placental abnormalities differ in small for gestational age neonates in relation to their prenatal sonographic abdominal circumference measurements

Background: Antenatal detection of abdominal circumference (AC) <10th percentile, among small for gestational age (SGA) neonates, probably reflects the severity of their growth restriction. We aimed to study neonatal outcome and placental pathology among SGA neonates in correlation to their AC measurements.Methods: Maternal and neonatal computerized medical records and placental histopathology reports of all SGA neonates, (neonatal birth-weight ≤10th percentile), born between 24 and 42 weeks, during 2015-2018 were reviewed. Included cases with fetal biometric measurements conducted up to 7 days prior labor. Results were compared between cases with sonographic antenatal AC <10th percentile and neonates with sonographic antenatal AC ≥10th percentile. Placental lesions were classified according to "Amsterdam" Placental workshop criteria.Results: The AC <10th percentile group (n = 148) was characterized by higher rate of nulliparity (p = .003), and induction of labor (p = .009), as compared to the AC ≥10th percentile group (n = 41). There were no between groups differences in the rate of maternal BMI (kg/m²), hypertensive disorders, diabetes or smoking. Neonatal hypoglycemia was more common in the AC <10th percentile group as compared to the AC ≥10th percentile group (p = .04). Placentas from the AC <10th percentile group were smaller (p < .001), with more MVM lesions (p = .02) and chronic villitis (p = .04). By multivariate regression analysis, AC <10th percentile and maternal hypertensive disorders, were found to be independently associated with placental MVM lesions, aOR = 2.43 (95% CI 1.04, 5.88) and aOR = 3.15 (95% CI 1.06, 9.31), respectively.Conclusions: Higher rate of placental maternal malperfusion lesions, chronic villitis, and more neonatal hypoglycemia characterize SGA neonates with AC <10th percentile, pointing to the importance of AC measurement as an indicator for placental insufficiency.

Placental proteases PAPP-A and PAPP-A2, the binding proteins they cleave (IGFBP-4 and -5), and IGF-I and IGF-II: Levels in umbilical cord blood and associations with birth weight and length

BACKGROUND

A newborn's birth weight for gestational age provides important insights into his or her fetal growth and well-being. While the underlying mechanisms regulating fetal growth remain to be fully elucidated, the IGF axis plays an important role. Some components of this axis have been well-characterized in umbilical cord blood, but others have not yet been studied. We measured the proteases PAPP-A and PAPP-A2, the binding proteins they cleave (IGFBP-4 and -5), and the established molecules IGF-I and -II in umbilical cord blood to better characterize the IGF axis in relation to birth weight and length.

METHODS

We performed a case-control study of 180 neonates born at a tertiary teaching hospital in Boston. To maximize power, infants were recruited in a 1:3:1 ratio with 37 SGA, 111 AGA, and 37 LGA infants matched by gestational age, sex, and delivery mode. IGF-I, IGF-II, IGFBP-4, IGFBP-5, PAPP-A, and PAPP-A2 were measured in umbilical cord blood by ELISA. Associations between birth weight and birth length Z-scores and the Z-scores of the above molecules were analyzed using linear regression models and analysis of covariance.

RESULTS

Birth weight and length Z-scores were positively associated with Z-scores of IGF-I, IGF-II, total IGFBP-4, and IGFBP-5, with IGF-I having the strongest association. Birth weight and length Z-scores were negatively associated with Z-scores of intact IGFBP-4, PAPP-A, and PAPP-A2 levels.

CONCLUSIONS

We confirm previous findings of significant associations between the IGFs in cord blood and newborn size and for the first time show positive associations between cord blood total IGFBP-4 and -5 and birth weight and a negative association between intact IGFBP-4 and birth weight. We also show for the first time a reciprocal relationship between cord blood levels of PAPP-A and PAPP-A2 and newborn size. The implications of these findings need to be further examined in large longitudinal studies and likely have diagnostic and therapeutic potential.

Early onset fetal growth restriction

Fetal growth restriction (FGR) diagnosed before 32 weeks is identified by fetal smallness associated with Doppler abnormalities and is associated with significant perinatal morbidity and mortality and maternal complications. Recent studies have provided new insights into pathophysiology, management options and postnatal outcomes of FGR. In this paper we review the available evidence regarding diagnosis, management and prognosis of fetuses diagnosed with FGR before 32 weeks of gestation.

Recapitulation of characteristics of human placental vascular insufficiency in a novel mouse model

OBJECTIVE

We tested the effects of selective reduction of placental blood flow by mesenteric uterine artery branch ligation (MUAL) resulting in fetal growth restriction (FGR).

METHODS

Timed mated C57BL/6J Day(D) 18 dams were divided into two groups: MUAL (n = 18); and control-sham (n = 18). Pups were delivered on D20, cross-fostered to surrogate CD-1 mothers for 4 weeks, and followed for 8 weeks. Outcome data included birth and placental weight, postnatal growth, placental volume determined by stereology, quantification of placental insulin-like growth factors-1(IGF-1) and IGF-2 and IGF binding proteins(IGFBP 2 and 6) by ELISA and gene expression by qPCR and GeneChip microarray analysis.

RESULTS

Compared with control, MUAL had an 11% reduction in mean birth weight (1.06 ± 0.13 g vs. 0.94 ± 0.13 g, p < 0.001) but no difference in placental weight. At 4 weeks of age, mean body weights of MUAL pups were significantly lower than sham. By 8 weeks, males but not females MUAL mice achieved equivalent mean body weight to control. Placental labyrinth depth, volume, and placental gene expression of IGF-1 and 2 were significantly reduced by MUAL. In contrast, placental protein level of IGFBP-2 and 6 were significantly elevated in the MUAL. Genomic expression analysis demonstrated that MUAL pups significantly up-regulated genes that were associated with apoptosis and growth pathways.

CONCLUSION

This novel mouse animal model of FGR using selective ligation recapitulates multiple characteristics of placental vascular insufficiency (PI) in humans. This is the first non-genetic mouse model of PI which offers its application in transgenic mice to better study the underlying mechanisms in PI.

CONDENSATION

A new mouse model of placental vascular insufficiency by selective ligation of mesenteric uterine artery branch recapitulates multiple findings observed in human placental vascular insufficiency.

The fetal response to chronic placental insufficiency

Fetal growth restriction is most commonly caused by failure of the placenta to meet the increasing demands for oxygen and substrate of the developing fetus, resulting in common fetal compensatory responses. Understanding these responses is helpful in developing a management strategy that will optimize pregnancy outcome.

Comparison of umbilical-artery velocimetry and cardiotocography for surveillance of small-for-gestational-age fetuses

Intrauterine growth retardation is associated with an increased risk of fetal asphyxia as well as greater perinatal morbidity and mortality. Ultrasound fetometry enables detection of fetuses that are small for gestational age. Doppler velocimetry of the umbilical artery has good predictive ability for fetal distress, but it is not yet clear whether it could replace cardiotocography in antenatal surveillance of small-for-gestational-age fetuses. We have done a randomised comparison of the two methods. At four obstetric departments in Sweden, women with fetuses found to be small on ultrasound examination at 31 completed weeks of pregnancy or later were randomly assigned to antenatal surveillance with either doppler velocimetry (doppler; 214) or cardiotocography (CTG; 212). Pregnancies in the doppler group were managed according to a protocol based on blood-flow classes deriving from the semiquantitative evaluation of umbilical-artery velocity waveforms; unless the pregnancy was complicated by any other disorder, no antenatal cardiotocography was done. By comparison with the CTG group, the doppler group had fewer monitoring occasions (mean 4.1 [SD 3.1] vs 8.2 [6.2], p < 0.01), antenatal hospital admissions (68 [31.3%] vs 97 [45.8%], p < 0.01), inductions of labour (22 [10.3%] vs 46 [21.7%], p < 0.01), emergency caesarean sections for fetal distress (11 [5.1] vs 30 [14.2%], p < 0.01), and admissions to neonatal intensive care (76 [35.5%] vs 92 [43.4%], p = 0.10). The groups did not differ in gestational age at birth, birthweight, Apgar scores, or total number of caesarean deliveries. Umbilical-artery doppler velocimetry of small-for-gestational-age fetuses allows antenatal monitoring and obstetric interventions to be aimed more precisely than does cardiotocography.

Proportionality of small for gestational age babies as a predictor of neonatal mortality and morbidity

Neonatal mortality and morbidity of 2609 babies who weighed less than the fifth centile for gestational age were studied in order to evaluate the relationship between the type of intrauterine growth retardation and the short-term prognosis after birth. Of these babies, 1175 had both a birthweight and head circumference below the fifth centile ('proportionately small'); the others, whose body weight was below but head circumference above the fifth centile, were defined as 'disproportionately small'. The former group showed a consistently higher risk of death during the neonatal period. Morbidity defined by birth asphyxia, respiratory distress and neonatal infections was higher in those proportionately small babies who were delivered at term. The picture reversed for hyperbilirubinaemia, which was more frequent among disproportionately small babies. Proportionality, defined on the basis of the correspondence between birthweight and head circumference centiles, appears to be a simple and non-invasive clinical method to identify babies who are at higher risk of adverse outcome.

Low human fetal heart rate variation in normal pregnancy

The fetal heart rates of 340 normal singleton pregnancies at 30-33 weeks gestation were screened using a microprocessor system on-line. Eleven fetuses (3.2%) with a heart rate variation less than the 5th centile were identified, of whom 10 were studied longitudinally. At 30-33 weeks the mean minute range of pulse intervals (a measure of fetal heart rate variation) was 31.4 (SE 1.5) ms compared with 51.0 (SE 3.4) ms in a randomly selected control group. The study group continued to have significantly lower fetal heart rate variation than controls on each of three subsequent occasions until delivery. There were no significant differences between the two groups in fetal outcome, which was good. This demonstrates that a small proportion of normal fetuses have consistently low heart rate variation, and helps to define the lower limit of the normal distribution of fetal heart rate variation. After delivery, there were no significant differences between heart rate or its variation between the two groups. We conclude that the lower prenatal heart rate variation in the study group was a consequence of the uterine environment.

Prenatal asphyxia, hyperlacticaemia, hypoglycaemia, and erythroblastosis in growth retarded fetuses

The umbilical venous oxygen and carbon dioxide tensions, pH, lactate and glucose concentrations, nucleated red cell (erythroblast) count, and haemoglobin concentration were measured in 38 cases of intrauterine growth retardation in which fetal blood sampling was performed by cordocentesis. The oxygen tension was below the normal mean for gestational age in 33 cases; in 14 it was below the lower limit of the 95% confidence interval for normal pregnancies. The severity of fetal hypoxia correlated significantly with fetal hypercapnia, acidosis, hyperlacticaemia, hypoglycaemia, and erythroblastosis. These findings indicate that "birth asphyxia" is not necessarily due to the process of birth.