What is the term given to a woman who has completed one pregnancy with a fetus or fetuses reaching the stage of fetal viability?

Interpretation

The absence of fetal cardiac activity and fetal movement after scanning for a 5-minute interval in a pregnancy of more than 20 weeks’ gestation is said to be 100% reliable for diagnosing a fetal demise. For a first-trimester pregnancy, if uncertainty exists about fetal heart activity, rescanning should be performed in 1 to 2 weeks.

Secondary criteria for fetal demise using POCUS include fetal anomalies such as hydrops, ascites, and pleural or pericardial effusions. Echogenic gas in the fetal heart and vessels may be early findings. Late findings include morphologic changes such as skeletal anomalies and unusual fetal positioning.

Reaction to external stimulation or uterine manipulation should cause brisk reflexes in viable fetuses, as opposed to the passive motions seen with a fetal demise. Avoid misinterpreting the passive motions from uterine contractions around a dead fetus as fetal activity.

Because abruptio placentae cannot always be diagnosed with ultrasound (i.e., it is a clinical diagnosis), ultrasound studies should be used in conjunction with maternal–fetal monitoring in the pregnant patient with significant abdominal trauma. A 4-hour monitoring period should be sufficient to identify fetal distress.

Viability of the Fetus

Fetal viability is a major issue that is dependent on the evolution and progress of modern neonatology (Beauthier, 2007). It is generally accepted that a 28-week-old fetus that doesn't need resuscitation is viable. However, according to WHO, fetal viability is possible after 20 weeks of fetal life (22 weeks of amenorrhea).Anthropometrical characteristics as well as clinical parameters of fetal age estimation are of high importance.

Determination of Fetal Age

A simple way to calculate fetal age (in lunar months) is to divide the fetal length (in cm) by 4 for fetuses less than 5 months' gestation. If it is less than 5 months' gestation the length (in cm) is divided by 5. Anthropometric measurements collected during examination of the fetus are used to estimate its age more accurately (Beauthier, 2011b). Three types of data can be gathered from radiologic investigations (Scheuer et al., 1980):

direct fetal age estimation from measurement of the length of long bones (Scheuer et al., 1980);

fetal age estimation from measurement of the long bones and calculation of fetal stature (crown–heel or crown–rump length) (O'Rahilly and Müller, 2001; Scheuer and Black, 2004); and

a more difficult method involving the degree of deciduous teeth calcification; this method requires the conservation of dental crowns and is not particularly suitable for this type of investigation.

Scheuer reports the following values from her study on full-term fetuses in the UK (Scheuer et al., 1980):

crown–rump length: from 28 to 32 cm; and

crown–heel length: from 48 to 52 cm.

Various authors have highlighted the importance of long bones radiography, in particular the fetal femoral diaphysis (Odita et al., 1982; Piercecchi-Marti et al., 2002). A study was carried out to investigate the fidelity and reproducibility of the radiographic methods used for measuring the femoral diaphysis (Adalian et al., 2001). The regression equation obtained was as follows:

Fetalage(inweeks)=6.93+0.434×femurlength(inmm)

The lower limb centers of ossification (distal epiphysis of the femur, proximal epiphysis of the tibia, posterior tarsus) are of great practical interest.

Echographic examination can provide useful information in the living subject.

Many studies have been carried out using ultrasonography, with a focus on the length of fetal long bones (Jeanty et al., 1984), the length of the femur, the relationship between the length of the femur and fetal weight (Honarvar et al., 2001), biparietal diameter, and cephalic and abdominal perimeters (Davis et al., 1993; Nasrat and Bondagji, 2005; Yagel et al., 1986). Using ultrasonography other authors have examined the relationship between fetal weight, abdominal perimeter, and femur length, and a mathematical model was proposed (Ferrero et al., 1994).

Table 2 shows some useful anthropometric and visceral parameters in the full-term fetus.

Table 2. Anthropometric and visceral parameters of the full-term fetus

Source: Beauthier, J-P., 2011a. La problématique du foetus et du nouveau-né en médecine légale. In: Beauthier, J-P. (Ed.), Traité de Médecine Légale. Bruxelles: De Boeck Université, pp. 389–402.

Signs Observed in the Stillborn Baby

Differentiating between the stillborn baby and the child who has not lived is not easy. The phenomena of maceration (aseptic autolysis which occurs when the fetus dies in utero) and putrefaction (postmortem ex utero deterioration) can notably complicate the medicolegal approach.

Descriptions of the criteria of extrauterine life are based on the existence of respiratory events and an effective circulatory system after birth. Cardiovascular function is evident in children who are victims of physical violence in particular (bruising, vital tegumentary lesions, associated fractures, and hemorrhage). Ventilatory function is assessed by histological study of the lung, and the presence or absence of territorial atelectasis is established. Multiple samples are required to clarify the matter.

Introduction

Assessments of the fetal well-being and cardiac function and identification of a likely disease mechanism are important diagnostic steps in the clinical evaluation of the fetus with cardiac compromise. Table 28.1 summarizes the echocardiographic features of the main conditions associated with in-utero HF. The prenatal diagnosis of HF primarily relies on the ultrasound-based documentation of systolic and/or diastolic cardiac dysfunction and the circulatory consequences [31].

Table 28.1. Echocardiographic Features of Conditions Associated With Fetal Heart Failure

CCAM, congenital cystic adenomatoid malformations of the lung; CHB, complete heart block; CM, cardiomyopathy; DA, ductus arteriosus; DV, ductus venosus; EFE, endocardial fibroelastosis; MCA, middle cerebral artery; N, normal; NC, ventricular noncompaction; RV > LV, right ventricle more severely affected than the left ventricle; TRAP, twin reversed arterial perfusion sequence; TTTS, twin–twin transfusion syndrome; ↑, increased; ↓, decreased; –, absent.

Measures of the Cardiovascular Status

In early stages of HF, disease manifestations that are readily detectable by echocardiography may be subtle. At more advanced stages (Fig. 28.1), findings include ascites, pleural effusion, pericardial effusion, or a combination of these findings, in addition to cardiomegaly, valvar regurgitation, poly- or oligohydramnios, preferential shunting of blood flow to the brain and heart, absence or reversal of the end-diastolic umbilical artery (UA) flow, and reduced or absent fetal movements. In end-stage HF, generalized skin edema is seen easily over the scalp and abdominal wall.

Measures of Cardiac Function

M-mode is useful to quantify the fetal systolic ventricular function by measurements of the changes in ventricular dimensions at the end of diastole (EDD) and of systole (ESD), respectively. Ventricular shortening fraction is calculated as SF (%) = (EDD-ESD)/EDD × 100. An LV or RV SF <28% suggests impaired ventricular systolic function. A low SF is most commonly related to myocardial disease or high afterload [32] and is usually seen in association with other functional consequences such as diastolic dysfunction, cardiomegaly, and atrioventricular (AV) valvar regurgitation [33,34].

Measurement of the peak velocity (vmax) of the AV regurgitation jet, if present, is a geometry-independent indirect measure of the ventricular contractile force. The peak pressure a ventricle is able to generate in the setting of AV regurgitation is estimated as pressure = 4 × (vmax)2 + atrial pressure. A normal fetal atrial pressure is about 3–4 mmHg and a normal mid- to late-gestational AV valvar pressure gradient is typically in the range of 40–60 mmHg [29]. A lower pressure gradient in the setting of moderate/severe AV regurgitation and reduced/absent forward flow across the pulmonary or aortic valve indicates subnormal pressure-generating capacity of the related ventricle.

CO (mL/min/kg) is a crude estimate of the global cardiac function and can be calculated as CO = VTI × π × (D2/4) × HR/estimated fetal weight [35]. VTI relates to the velocity–time integral of the systolic aortic or pulmonary flow, D to the annulus diameter of the corresponding valve, and HR to the fetal heart rate. CO is not routinely measured but is useful to detect and monitor conditions associated with high-output failure such as AV malformations or vascular tumors [36–41].

Doppler flow profiles of the ventricular inflow, the systemic veins, and the DV provide crucial information on ventricular relaxation and compliance during diastole [42–44]. Normal fetal ventricular filling across the AV valves consists of three phases: (1) isovolumetric relaxation preceding ventricular inflow (IVR); (2) early passive filling (E-wave); and (3) late active filling during atrial contraction (A-wave). At a normal fetal heart rate, the duration of the IVR is <43 ms, and the Doppler inflow pattern is biphasic with a dominant A-wave as diastolic ventricular filling mainly results from atrial contraction [42,45]. Venous forward flow is initiated with the opening of the AV valves in early diastole, which causes an immediate drop in atrial pressure. Forward flow then slowly decreases with increasing ventricular pressure as the ventricles fill. With the onset of atrial contraction in late diastole there is a sudden increase in atrial pressure, which briefly slows the forward flow in the DV and briefly reverses the flow in the hepatic and caval veins away from the heart (a-waves). Doppler flows compatible with normal diastolic ventricular function include the following: (1) antegrade DV flow throughout the entire cardiac cycle; (2) a-wave flow reversal of <20 cm/s in the inferior vena cava; and (3) the absence of UV pulsations [46,47]. Biventricular diastolic dysfunction is very poorly tolerated by the fetus. The diagnosis of compromised diastolic filling is made on the detection of abnormal Doppler flows across the AV valves (monophasic, short inflow, or low E/A ratio; prolonged IVR interval), the DV (absent or reversed a-wave), and the inferior vena cava (a-wave reversal >20 cm/s) (Fig. 28.2). The presence of umbilical venous pulsations is a most useful predictor of imminent perinatal death in fetal hydrops.

The myocardial performance index (MPI) is a combined measure of systolic and diastolic ventricular function and is calculated as the sum of the mitral or tricuspid isovolumetric relaxation and contraction times divided by the aortic or pulmonary ejection time, for the LV or RV, respectively. Doppler-derived MPI values above 0.48 are considered abnormal [48].

Heart Failure Score

The cardiovascular profile score (CVPS) is a composite scoring system that is used to grade the severity of fetal HF [49–51]. The score is based on the result of five ultrasound parameters that have been correlated with poor fetal outcome (Table 28.2): (1) cavity effusions; (2) venous Doppler; (3) cardiothoracic area ratio (CTR); (4) cardiac function; and (5) UA Doppler. Severity of HF is rated on a 10 point scale, and 1 or 2 points are deducted for abnormalities of each component marker. The degree of failure is graded as being absent (10 points), mild (8 or 9 points), moderate (6 or 7 points), or severe (<5 points). One point is deducted from the score at the detection of each of the following findings: (1) isolated effusion; (2) DV a-wave flow reversal; (3) CTR of 35%–50%; (4) holosystolic tricuspid regurgitation or SF <28%; and (5) absent end-diastolic UA flow. Two points are deducted with each of these findings: (1) skin edema; (2) pulsatile UV flow; (3) CTR >50%; (4) holosystolic mitral regurgitation or monophasic AV inflow; and (5) end-diastolic UA flow reversal.

Table 28.2. Cardiovascular Profile to Assess the Severity of Heart Failure Based on the Combined Result of Five Echocardiographic Variables. The Heart Failure Score is 10 if There Are no Abnormal Signs and Reflects Two Points for Each of Five Categories: Hydrops; Venous Doppler; Heart Size; Cardiac Function; and Arterial Doppler

AEDV, absent end-diastolic velocity; dP/dt, change in pressure over time of TR jet; DV, ductus venosus; LV, left ventricle; MR, mitral valve regurgitation; MV, mitral valve; pts, points; REDV, reversed end-diastolic velocity; RV, right ventricle; SF, ventricular shortening fraction; TR, tricuspid valve regurgitation; TV, tricuspid valve; UV, umbilical vein.

Using a modified CVPS from the original scoring system (replacement of “skin edema” with “fetal hydrops” and elimination of “tricuspid valve dP/dt” as 2-point criteria) in a study of fetal patients with primary forms of cardiomyopathy (CM), a lower score at the baseline exam was already significantly associated with mortality (hazard ratio: 1.45 per point decrease; 95% confidence interval: 1.16–1.79; P = .001) despite the potential of disease progression later in gestation or after birth: 1-year survival on diagnosis was 24% with a score ≤6 but 79% with a score of 7 or higher [51]. While this supports that the modified CVPS is a useful prognostic marker for fetal CM, it is important to recognize that its predictive value depends on the HF cause and whether treatment is available. For example, HF in an anemic fetus with acute parvovirus infection can be treated with blood transfusions and is expected to have a better outcome compared with a fetus with CM and the same low CVPS.

Assessing fetal condition

Different checks are regularly made on the fetus to monitor how they are coping with labour. If it is deemed that the fetus is not coping, then interventions may be made either to speed up labour or deliver the fetus instrumentally.

Bodywork implications

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The client may need more support to get into comfortable positions.

The client may need emotional support as she may get worried about her baby.