Sonographic Estimation of Fetal Age and Weight

External validation of models to estimate gestational age in the second and third trimester using ultrasound: A prospective multicentre observational study

OBJECTIVES

Accurate assessment of gestational age (GA) is important at both individual and population levels. The most accurate way to estimate GA in women who book late in pregnancy is unknown. The aim of this study was to externally validate the accuracy of equations for GA estimation in late pregnancy and to identify the best equation for estimating GA in women who do not receive an ultrasound scan until the second or third trimester.

DESIGN

This was a prospective, observational cross-sectional study.

SETTING

57 prenatal care centres, France.

PARTICIPANTS

Women with a singleton pregnancy and a previous 11-14-week dating scan that gave the observed GA were recruited over an 8-week period. They underwent a standardised ultrasound examination at one time point during the pregnancy (15-43 weeks), measuring 12 foetal biometric parameters that have previously been identified as useful for GA estimation.

MAIN OUTCOME MEASURES

A total of 189 equations that estimate GA based on foetal biometry were examined and compared with GA estimation based on foetal CRL. Comparisons between the observed GA and the estimated GA were made using R2, calibration slope and intercept. RMSE, mean difference and 95% range of error were also calculated.

RESULTS

A total of 2741 pregnant women were examined. After exclusions, 2339 participants were included. In the 20 best performing equations, the intercept ranged from -0.22 to 0.30, the calibration slope from 0.96 to 1.03 and the RSME from 0.67 to 0.87. Overall, multiparameter models outperformed single-parameter models. Both the 95% range of error and mean difference increased with gestation. Commonly used models based on measurement of the head circumference alone were not amongst the best performing models and were associated with higher 95% error and mean difference.

CONCLUSIONS

We provide strong evidence that GA-specific equations based on multiparameter models should be used to estimate GA in late pregnancy. However, as all methods of GA assessment in late pregnancy are associated with large prediction intervals, efforts to improve access to early antenatal ultrasound must remain a priority.

TRIAL REGISTRATION

The proposal for this study and the corresponding methodological review was registered on PROSPERO international register of systematic reviews (registration number: CRD4201913776).

Indicated vs universal third-trimester ultrasound examination in low-risk pregnancies: a pre-post-intervention study

BACKGROUND

In low-risk pregnancies, a third-trimester ultrasound examination is indicated if fundal height measurement and gestational age discrepancy are observed. Despite potential improvement in the detection of ultrasound abnormality, prior trials to date on universal third-trimester ultrasound examination in low-risk pregnancies, compared with indicated ultrasound examination, have not demonstrated improvement in neonatal or maternal adverse outcomes.

OBJECTIVE

The primary objective was to determine if universal third-trimester ultrasound examination in low-risk pregnancies could attenuate composite neonatal adverse outcomes. The secondary objectives were to compare changes in composite maternal adverse outcomes and detection of abnormalities of fetal growth (fetal growth restriction or large for gestational age) or amniotic fluid (oligohydramnios or polyhydramnios).

STUDY DESIGN

Our pre-post intervention study at 9 locations included low-risk pregnancies, those without indication for ultrasound examination in the third trimester. Compared with indicated ultrasound in the preimplementation period, in the postimplementation period, all patients were scheduled for ultrasound examination at 36.0-37.6 weeks. In both periods, clinicians intervened on the basis of abnormalities identified. Composite neonatal adverse outcomes included any of: Apgar score ≤5 at 5 minutes, cord pH <7.00, birth trauma (bone fracture or brachial plexus palsy), intubation for >24 hours, hypoxic-ischemic encephalopathy, seizure, sepsis (bacteremia proven with blood culture), meconium aspiration syndrome, intraventricular hemorrhage grade III or IV, periventricular leukomalacia, necrotizing enterocolitis, stillbirth after 36 weeks, or neonatal death within 28 days of birth. Composite maternal adverse outcomes included any of the following: chorioamnionitis, wound infection, estimated blood loss >1000 mL, blood transfusion, deep venous thrombus or pulmonary embolism, admission to intensive care unit, or death. Using Bayesian statistics, we calculated a sample size of 600 individuals in each arm to detect >75% probability of any reduction in primary outcome (80% power; 50% hypothesized risk reduction).

RESULTS

During the preintervention phase, 747 individuals were identified during the initial ultrasound examination, and among them, 568 (76.0%) met the inclusion criteria at 36.0-37.6 weeks; during the postintervention period, the corresponding numbers were 770 and 661 (85.8%). The rate of identified abnormalities of fetal growth or amniotic fluid increased from between the pre-post intervention period (7.1% vs 22.2%; P<.0001; number needed to diagnose, 7; 95% confidence interval, 5-9). The primary outcome occurred in 15 of 568 (2.6%) individuals in the preintervention and 12 of 661 (1.8%) in the postintervention group (83% probability of risk reduction; posterior relative risk, 0.69 [95% credible interval, 0.34-1.42]). The composite maternal adverse outcomes occurred in 8.6% in the preintervention and 6.5% in the postintervention group (90% probability of risk; posterior relative risk, 0.74 [95% credible interval, 0.49-1.15]). The number needed to treat to reduce composite neonatal adverse outcomes was 121 (95% confidence interval, 40-200). In addition, the number to reduce composite maternal adverse outcomes was 46 (95% confidence interval, 19-74), whereas the number to prevent cesarean delivery was 18 (95% confidence interval, 9-31).

CONCLUSION

Among low-risk pregnancies, compared with routine care with indicated ultrasound examination, implementation of a universal third-trimester ultrasound examination at 36.0-37.6 weeks attenuated composite neonatal and maternal adverse outcomes.

Diagnosis of Pregnancy Complications Using Blind Ultrasound Sweeps Performed by Individuals Without Prior Formal Ultrasound Training

OBJECTIVE

To estimate the diagnostic accuracy of blind ultrasound sweeps performed with a low-cost, portable ultrasound system by individuals with no prior formal ultrasound training to diagnose common pregnancy complications.

METHODS

This is a single-center, prospective cohort study conducted from October 2020 to January 2022 among people with second- and third-trimester pregnancies. Nonspecialists with no prior formal ultrasound training underwent a brief training on a simple eight-step approach to performing a limited obstetric ultrasound examination that uses blind sweeps of a portable ultrasound probe based on external body landmarks. The sweeps were interpreted by five blinded maternal-fetal medicine subspecialists. Sensitivity, specificity, and positive and negative predictive values for blinded ultrasound sweep identification of pregnancy complications (fetal malpresentation, multiple gestations, placenta previa, and abnormal amniotic fluid volume) were compared with a reference standard ultrasonogram as the primary analysis. Kappa for agreement was also assessed.

RESULTS

Trainees performed 194 blinded ultrasound examinations on 168 unique pregnant people (248 fetuses) at a mean of 28±5.85 weeks of gestation for a total of 1,552 blinded sweep cine clips. There were 49 ultrasonograms with normal results (control group) and 145 ultrasonograms with abnormal results with known pregnancy complications. In this cohort, the sensitivity for detecting a prespecified pregnancy complication was 91.7% (95% CI 87.2-96.2%) overall, with the highest detection rate for multiple gestations (100%, 95% CI 100-100%) and noncephalic presentation (91.8%, 95% CI 86.4-97.3%). There was high negative predictive value for placenta previa (96.1%, 95% CI 93.5-98.8%) and abnormal amniotic fluid volume (89.5%, 95% CI 85.3-93.6%). There was also substantial to perfect mean agreement for these same outcomes (range 87-99.6% agreement, Cohen κ range 0.59-0.91, P<.001 for all).

CONCLUSION

Blind ultrasound sweeps of the gravid abdomen guided by an eight-step protocol using only external anatomic landmarks and performed by previously untrained operators with a low-cost, portable, battery-powered device had excellent sensitivity and specificity for high-risk pregnancy complications such as malpresentation, placenta previa, multiple gestations, and abnormal amniotic fluid volume, similar to results of a diagnostic ultrasound examination using a trained ultrasonographer and standard-of-care ultrasound machine. This approach has the potential to improve access to obstetric ultrasonography globally.

Smoking cessation Through Optimisation of clinical care in Pregnancy: the STOP randomised controlled trial

BACKGROUND

Cigarette smoking negatively impacts on maternal and fetal health. Smoking cessation is one of the few interventions capable of improving pregnancy outcomes. Despite the risks, the most effective antenatal model of care for smokers is still unclear, and specific recommendations for screening for fetal growth restriction are absent.

METHODS

This is a pragmatic randomised controlled trial of a dedicated smoking cessation clinic versus routine antenatal care as an intervention to reduce cigarette smoking behaviour. Smoking mothers randomised to the Smoking cessation Through Optimisation of clinical care in Pregnancy (STOP) clinic will have all antenatal care provided by a team comprising an obstetrician, a midwife, and a smoking cessation practitioner. This intervention includes ultrasound screening for fetal growth restriction. The control arm comprises two groups: one receiving standard care with ultrasound screening for fetal growth restriction, and one receiving standard care with ultrasound screening for growth restriction only if clinically indicated by their healthcare provider. Four hundred and fifty women will be recruited and randomised to either intervention or control arms stratifying for age, parity, and history of fetal growth restriction.

RESULTS

The primary outcome is self-reported, continuous abstinence from smoking between the quit date and end of pregnancy, validated by exhaled carbon monoxide or urinary cotinine. The quit date is targeted as being at or before 16 weeks' gestation and no further than 28 weeks' gestation. The secondary outcomes are a set of variables including maternal and fetal morbidity and mortality, neonatal complications and delivery outcomes, smoking and psychological outcomes, and qualitative measures.

CONCLUSIONS

Despite much research into cigarette smoking in pregnancy, the optimal model of care for these women is still unknown. This study has the potential to improve the model of antenatal care provided to pregnant women who smoke and to improve outcomes for both mother and infant.

TRIAL REGISTRATION

ISRCTN11214785 . Registered on 8 February 2018.

Maternal nutrient intake and fetal gastroschisis: A case-control study

Fetal gastroschisis is a paraumbilical abdominal wall defect with herniation of the abdominal organs. This multifactorial malformation occurs in young pregnant women, and the underlying cause of the disease remains unknown; however, nutritional factors may play a role in its development. This case-control study explored the association of maternal nutrient intake with the occurrence of gastroschisis. The gastroschisis group (GG) comprised 57 pregnant women with fetuses with gastroschisis, and the control group (CG) comprised 114 pregnant women with normal fetuses matched for maternal age, gestational age, and preconception body mass index classification. Nutritional assessments related to the preconception period were obtained using the food consumption frequency questionnaire, and nutrient intakes were calculated using nutrition programs. The median daily calorie intake was higher (2,382.43 vs. 2,198.81; p = .041) in the GG than in the CG. The median intake of methionine (763.89 vs. 906.34; p = .036) and threonine (1,248.34 vs. 1,437.01; p = .018) was lower in the GG than in the CG. Pregnant women with fetuses with gastroschisis have a diet characterized by higher calorie intake and lower levels of essential amino acids (methionine and threonine) during the preconception period than pregnant women with normal fetuses.

Prediction of intrapartum Cesarean delivery for non-reassuring fetal status after a successful external cephalic version by a low pre-version pulsatility index of the fetal middle cerebral artery

OBJECTIVE

To determine whether a pre-version Doppler assessment of fetal cerebral and umbilical blood flow can predict the ultimate need for intrapartum Cesarean delivery after a successful external cephalic version (ECV).

METHODS

A prospective observational study on women undergoing ECV between 36 and 38 gestational weeks was performed over a 5-year period. The pulsatility index (PI) of the fetal middle cerebral artery (MCA) and umbilical artery, heart rate and amniotic fluid index were measured before ECV. Women who had successful ECV were then divided into three groups according to the mode of delivery: (1) vaginal delivery, (2) intrapartum Cesarean delivery for poor progress and (3) intrapartum Cesarean delivery for non-reassuring fetal status. The fetal blood flow parameters were compared between the groups. Potential predictors were further analyzed using receiver-operating characteristics curves.

RESULTS

Of 174 women with successful ECV, 140 (80.5%) had vaginal delivery, 19 (10.9%) required emergency intrapartum Cesarean delivery for non-reassuring fetal status and 15 (8.6%) for poor progress. MCA-PI was significantly lower in the group with non-reassuring fetal status. MCA-PI is predictive of intrapartum Cesarean delivery (area under the curve = 0.68, P = 0.021). The sensitivity and specificity at a cut-off level of 1.4 were 62.5% and 76%, respectively, while at a cut-off level of 1.5 they were 68.8% and 63.5%, respectively.

CONCLUSION

Intrapartum Cesarean delivery for non-reassuring fetal status after successful ECV is associated with a lower pre-version fetal MCA-PI.

Time domain measurement of blood flow in the human fetal aorta during normal pregnancy

OBJECTIVE

To evaluate blood-volume flow-rate measurement in the fetal descending thoracic aorta using a non-invasive, non-Doppler, ultrasound technique.

METHODS

This was a cross-sectional, observational study. Volume flow measurements were obtained from the descending thoracic aorta in 59 human fetuses between 20 and 40 weeks' gestation. These were uncomplicated pregnancies that resulted in the live births of appropriately grown infants. The measurements were obtained using a time domain processing technique: color velocity imaging quantification (CVI-Q).

RESULTS

The blood-volume flow rate increased consistently from the second trimester until term. The mean values ranged between 100 mL/min at 20 weeks' gestation and approximately 350 mL/min at term. The normalized (weight-adjusted) volume flow rates decreased with increasing gestation, from a maximum of 626 mL/min/kg at 23 weeks to a minimum of 45.6 mL/min/kg at 37 weeks.

CONCLUSIONS

The regular measurement of blood-volume flow in the descending fetal thoracic aorta is feasible using CVI-Q. Although there is a considerable learning curve, with adequate training there are potential clinical applications for this non-Doppler technique. However, limitations exist with the currently available technology for clinical use in fetal vascular studies.

The assessment of normal fetal liver volume by three-dimensional ultrasound

Liver volume (LIVV) is very important in determining the status of fetal growth. However, to measure human fetal LIVV in utero precisely and noninvasively is not an easy task. With the recent advancement of three-dimensional (3-D) ultrasound (US), the limitation in assessing fetal LIVV by 2-D US can be overcome. The purpose of this study was to establish a normal reference chart of fetal LIVV for clinical use. A prospective and cross-sectional study using 3-D US was undertaken to assess the fetal LIVV in normal pregnancy. In total, 226 singleton fetuses ranging between 20 and 40 weeks of gestation and fitting the criteria of normal pregnancies were enrolled in this study. Our results showed that fetal LIVV is highly correlated with the gestational age (GA). Furthermore, using GA as the independent variable and fetal LIVV as the dependent variable, the best-fit regression equation was LIVV (mL) = -398.26 + 46.199 xGA - 1.7567 x GA(2) + 0.0236 x GA(3) (r = 0.97, n = 226, p < 0.0001), with SD of LIVV (mL) = 1.2533 x (0.77956 + 0.17267 x GA). These common indexes of fetal biometry, such as biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HCi), abdominal circumference (ACi), femur length (FL), and estimated fetal weight (EFW), were all highly correlated with fetal LIVV (all p < 0.0001). In conclusion, our data of fetal LIVV assessed by 3-D US can serve as a useful reference in evaluating fetal growth status during normal gestation.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Three-dimensional ultrasound assessment of fetal liver volume in normal pregnancy: a comparison of reproducibility with two-dimensional ultrasound and a search for a volume constant

The purposes of this study are to compare the reproducibility of two-dimensional ultrasound (2DUS) and three-dimensional ultrasound (3DUS) in the assessment of fetal liver volume (LV), and to test whether the fetal LV assessed by the traditional method with 2DUS is equal to that with 3DUS in normal pregnancy. If significantly different, we then try to calculate a new constant of fetal LV for the traditional equation from the LV values obtained with 3DUS. In total, 30 normal singleton fetuses with gestational ages ranging from 20 to 30 weeks were included for the reproducibility test and 55 cases ranging from 20 to 31 weeks gestation were enrolled for finding a new volume constant of LV. The results showed that 3DUS is superior to 2DUS in the reproducibility test of fetal LV assessment. Moreover, the LV assessed with the traditional 2DUS method (identified as LV_42) was significantly smaller than that measured with 3DUS (P < 0.001). If the traditional 2DUS equation is to be used, the multiplying factor in the equation for the calculation of LV should be modified to 0.55 (SE = 0.017, N = 55). With the new volume constant, the new derived LV with 2DUS (identified as LV 55) was not different from that with 3DUS (identified as LV_3D). In conclusion, we recommend that 3DUS, instead of 2DUS, should be used for reaching an accurate assessment of fetal LV. Otherwise, applying our new volume constant may be of help in detecting abnormal fetal liver growth when only 2DUS is available.