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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5786_Библиотеки_им_академика_М_И_Перельмана.pdf
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FETAL BREATHING IN NORMAL PREGNANCY
Fetal breathing movements are characterized by a fluent downward movement of
the diaphragm, outward displacement of the abdomen and inward displacement
of the thorax. Apnoea is defined as an interval between two consecutive breaths
of more than 6 seconds. The incidence of fetal breathing increases up to about
30 weeks of gestation. At 20 weeks, breathing is on average present during 5%
of recording time and at 30 weeks during 30%. Fetal breathing movements are
affected by maternal meals and plasma glucose concentrations, especially during
the third trimester of pregnancy. The highest incidence occurs 1.5–2 hours after
a meal and 1 hour after the highest blood glucose value. There is also an increase
in breathing incidence at night, but this is related to a circadian rhythm and not
to glucose concentrations.
30
NORMAL DEVELOPMENT OF FETAL BEHAVIOURAL STATES
During early gestation movements are scattered over time, but in the course
Ultrasound in obstetrics and gynaecology
of pregnancy a progressive clustering occurs in rest/activity cycles and later in
behavioural states. These behavioural states develop during the third trimester
of pregnancy. They are distinct and discontinuous modes of neural activity and,
although defined by a different set of variables, are homologous to the states in
the newborn.28 Each state is defined by a specific combination of the parameters
of three selected variables: fetal heart rate pattern, body and eye movements.
Such a combination is relatively stable, i.e. it is maintained uninterrupted over
longer periods and transitions from one state to another are characterized by the
almost simultaneous change of state variables. In the healthy fetus behavioural
states are fully developed from about 36 weeks onwards, an age at which behavioural states are also present in low-risk preterm newborn infants.
In the near-term human fetus four behavioural states have been identified:
1F–4F (F stands for fetal).28 State 1F is characterized by a stable heart rate with
a small oscillation bandwidth (FHR pattern A) and absence of eye and generalized body movements. In state 2F, eye movements and periodic body movements
are present; fetal heart rate has a wide oscillation bandwidth between frequent
accelerations (FHR pattern B). In state 3F body movements are absent, eye movements are present and fetal heart rate has a wide oscillation bandwidth without accelerations (FHR pattern C). In state 4F there are prolonged accelerations
(FHR pattern D), numerous body movements and presence of eye movements. If
a stable association of the three state parameters exists for at least 3 minutes and
if transitions from one state to another do not last more than 3 minutes, the presence of fetal behavioural states is accepted. The fetal states correspond to state 1
to state 4 in the full-term newborn infant, and in the neonate they may also be
classified as quiet sleep, REM sleep, quiet awake and active awake, respectively.
An example of a fetal behavioural state recording is shown in Figure 15.4.
Fetal behavioural states develop gradually and from 28 weeks onwards there
276
is a significant association between the state variables.48 This development results
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180
120
FHR
GM
EM
D
A
2 F
1 F
+
−
+
−
B
C
FHRP
GM
EM
C 2F
0306090 120 150 180
Minutes
C 1F C 2F C 1F C 2F
STATE
Fig. 15.4 Example of a 3-h recording of a healthy fetus at 38 weeks of gestation. It shows
from above downwards: (1) the fetal heart rate tracing (FHR) and the occurrence of general
movements (GM) and eye movements (EM). Three periods of high heart rate variation
(pattern B) were interrupted by two periods of low variation (pattern A); during the former
both general movements and eye movements were present (coincidence 2F), but absent
during pattern A (coincidence 1F); (2) profiles of the three state variables and the resulting
episodes of coincidence 1F and 2F; (3) presence of behavioural states 1F and 2F (transitions
<3 min).
Fetal movement patterns and behavioural states
in a decrease in the occurrence of no coincidence, i.e. of the percentage of time
during which state criteria are not met.
2,28
In the near-term fetus state 1F is on
average present for about 35% of the time and state 2F for 50%; states 3F and 4F
or episodes of no coincidence account for the remaining 15%. The mean duration
of an enclosed epoch of state 2F is 65 minutes and that of state 1F approximately
25 minutes, which results in a complete sleep cycle of about 90 minutes. Near
term, an episode of state 1F may last for up to 45 minutes.
Fetal behavioural states are associated with other physiological phenomena.
For instance, it has been shown that the fetal micturition cycle is related to states,
with voiding occurring at or after a change from low to high heart rate variation.45 Fetal blood flow velocity waveforms, indicative of vascular resistance, are
also related to states and during 2F a lower resistance in the descending aorta
and internal carotid artery has been found.42 This implies that in relation to
these measurements, fetal behavioural states must be taken into account. The
latter also holds true for fetal heart rate monitoring: episodes of low heart rate
variation may be indicative of a poor fetal condition, but may also be physiological and part of state 1F.
Behavioural state organization in the human fetus is not easily influenced by
maternal or environmental factors. Hitherto, it has been found that in normal
pregnancy, state 1F is not influenced by Braxton Hicks contractions25 and uterine contractions during labour13 nor by induced maternal emotions,41 shaking
the maternal abdomen49 and transabdominal sound stimulation.37 These findings are in line with the fact that it is difficult to wake up a newborn infant
when in state 1. The fetus may benefit from this inaccessibility as it guarantees a
more or less undisturbed endogenous development. However, fetuses do react to
277
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vibroacoustic stimulation using an electronic artificial larynx and during the past
5 years, numerous papers on the use of this device have been published. The most
important rationale for stimulation is to differentiate between poor and good
fetal health in cases of suspect FHR patterns, e.g. low heart rate variation. This
kind of stimulus induces excessive fetal movements, a prolonged tachycardia and
disorganized behavioural states.47 Therefore, it seems better not to use this device,
especially as it induces intrauterine sound levels exceeding 125 dB.
29
ABNORMAL CONDITIONS AFFECTING FETAL MOVEMENT
PATTERNS (TABLE 15.1)
ALTERED BRAIN OR MUSCULAR DEVELOPMENT
Abnormal movement patterns, indicative of altered brain or muscular development, have been described in fetuses with chromosome abnormalities,7 in
anencephalic fetuses,46 in fetuses with other cerebral malformations, in growthretarded fetuses3 and in fetuses suffering from prolonged oligohydramnios.38
Ultrasound in obstetrics and gynaecology
Common features in all these cases are the qualitative changes in the execution
of movement patterns, which are abrupt and forceful, with large amplitude, in
the majority of fetuses with a chromosome or central nervous system defect
and slow, with small amplitude, in the others. Fetal seizures have been described
in association with severe brain abnormalities.
movement abnormalities associated with central nervous system dysfunction are
mainly qualitative and not quantitative in nature. In preterm babies with brain
lesions, assessment of the quality of movements appears to be a much better predictor of neurological outcome than the number of movements.31 In anencephalic fetuses movements tend to be numerous, forceful, jerky in character and of
1
It should be emphasized that
278
Table 15.1 Alterations in fetal behaviour in cases of fetal (central nervous system)
anomalies, growth retardation and maternal diabetes or induced by exogenous teratogens
and stimulation
Fetal movements
Emergence Quantity Quality Sleep states
Congential malformations + +
Maternal diabetes + + +
Intrauterine growth retardation + + +
Alcohol + +
Caffeine +
Cocaine + +
Corticosteroids +
Maternal stress +
Vibroacoustic stimulation + +
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FHR
variation
321
Time (weeks)
0
General
movements
Breathing
movements
a large amplitude.46 This indicates that only minimal neural structures are necessary for movements to be generated. On the other hand, these data indicate that
already in the first half of pregnancy a normal nervous system, although only
partly developed, is necessary for movements to be executed normally.
Prospective studies of behavioural development in fetuses affected by neuromuscular disorders or restrictive dermopathy are scarce.
19,22
The existing evidence
shows that absence or low levels of fetal body and limb movements, breathing
activity and mouth movements (sucking and swallowing) usually lead to the
almost simultaneous occurrence of joint contractures, pulmonary hypoplasia, and
facial anomalies and polyhydramnios, respectively. This phenomenon is known as
the fetal akinesia deformation sequence (FADS).
Data on abnormal behaviour in individual fetuses with abnormal brain functioning are still rare. Prenatal prediction of neurological outcome on the basis of
altered fetal behaviour is likely to remain difficult and requires extensive knowledge of normal movements and different diagnostic approaches.
INTRAUTERINE GROWTH RETARDATION (IUGR)
In IUGR fetuses movements are slow with a small amplitude.3 The development
of fetal behavioural states is delayed and/or altered, in such a way that the percentage of no coincidence is increased with a ‘redistribution’ of coincidence 2F
to coincidence 1F, i.e. towards an increase of a less active state.
precede the occurrence of fetal heart rate abnormalities and, therefore, of fetal
hypoxaemia. Brain dysfunction in these fetuses is therefore more likely the result
of chronic malnutrition in utero than due to hypoxaemia.
Changes in the quantity of fetal movements are rather late signs of impairment
and occur after the onset of fetal heart rate abnormalities. This has been found
both for the components of the biophysical profile score14 and in longitudinal
ultrasound observations (Fig. 15.5): fetal body movements decline in incidence at
2,12
These changes
Fetal movement patterns and behavioural states
Fig. 15.5 Time-related changes in fetal general movements, breathing movements and fetal
heart rate (FHR) variation with progressive deterioration of the fetal condition. The dashed
line represents the lower limit of the normal range for the biophysical variables studied (data
extracted from reference 35, with permission).
279
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or after the occurrence of fetal hypoxaemia and this is most likely due to adaptation.33 With further deterioration there is usually a rapid decline in heart rate
variation and in body and breathing movements, associated with poor fetal condition (acidaemia).
MATERNAL DIABETES
In women with type 1 diabetes, embryonic movements emerge during the first
trimester of pregnancy about 1 week later than in control fetuses, apart from
fetal breathing which starts earlier.26 During the third trimester fetal behavioural
states are less well organized, indicating a delayed or disturbed development of
nervous system functioning.24 The percentage of no coincidence is related to the
degree of (early) embryonic growth delay during the first trimester27 and these
data stress the importance of the effects of early disturbances in development
on nervous system functioning at the end of pregnancy. These data are consistent with those of Bloch Petersen et al,6 who found a relationship between early
embryonic growth delay and impaired development at 4 years of age.
Ultrasound in obstetrics and gynaecology
PRETERM CONTRACTIONS AND/OR RUPTURE OF MEMBRANES
The presence of fetal breathing movements in women admitted with preterm
contractions and intact membranes is a reassuring sign and less than 10% of them
will have delivered within a week (positive predictive value 93%: Table 15.2).
The negative predictive value is considerably lower (±67%). In other words, the
presence of fetal breathing movements is one of the best markers of low risk
for preterm delivery in women being admitted with contractions. This may be
explained by the fact that fetal breathing movements usually disappear during
labour, most likely because of increased prostaglandin levels. The negative predictive value of breathing movements is lower and this is due to the episodic character of breathing movements. The predictive value of fetal breathing movements
in cases of preterm rupture of membranes (PROM) is considerably lower (see
Table 15.2). The risk of intrauterine infection in cases of PROM is generally low if
fetal breathing is present (±15%) and high in the absence of breathing (±55%).
4,11
280
Table 15.2 Presence of fetal breathing movements (FBM) as a predictor of preterm delivery
in cases admitted because of preterm contractions with intact membranes (n= 219, 5 studies)
or rupture of membranes (n= 41, 3 studies)
Intact membranes (5 studies) Rupture of membranes (3 studies)
Continued
≥2 days
FBM(+) 166 10 176 9 6 15
FBM(−) 11 32 43 0 26 26
n 177 42 219 9 32 41
n 177 42 219 9 32 41
Delivered
<2 days
n Continued
≥2 days
Delivered
<2 days
n
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DRUGS, MEDICATION, STRESS AND FETAL STIMULATION
By studying the fetal behaviour, effects of exogenous behavioural teratogens
may be identified. Some investigators think that observation of fetal reactions to
(repetitive) stimuli may give insight into fetal brain integrity.
In a carefully controlled study, we found that two glasses of white wine temporarily suppress fetal breathing movements and disturb fetal state cycling, the
latter being mainly due to suppression of fetal eye movements.21 REM sleep is
important for normal brain development and these data may shed some light on
behavioural abnormalities observed in infants whose mothers consumed more
than two glasses of alcohol per day during pregnancy. A study like this one, demonstrating direct effects of alcohol on the fetus, may discourage pregnant women
from drinking.
Maternal caffeine intake causes considerable increases in fetal body movements and in the percentage of fetal heart rate variability pattern D, indicating
that the fetus spends more time ‘awake’.
Induced maternal emotions do not affect fetal state cycling, but there is a
positive correlation between the level of maternal stress and the incidence of
fetal body movements.41 Active fetuses also tend to have a high activity level
after birth and one may speculate whether this is due to prenatal effects of high
maternal anxiety or to genetic differences. The relationship between maternal
stress and fetal and neonatal behaviour is complex, given the large variety of
stressors and differences in ‘coping’ with stress. Moreover, maternal stress and
cortisol do not show a clear relationship. Exogenous corticosteroids induce a temporary reduction in fetal movements and fetal activity is inversely correlated to
the maternal diurnal cortisol rhythm.
further exploration.
Betametasone, administered to the mother to enhance fetal lung maturation
in case of threatened preterm delivery, results in a 50% reduction of body movements and in an almost complete cessation of fetal breathing on days 2 and 3
after the first administration.10 Also heart rate variation is temporarily reduced
and due account of this phenomenon has to be taken when monitoring the fetus.
These effects are not due to fetal hypoxaemia, but most likely to binding of this
corticosteroid to receptors in the brainstem. There is evidence that the reductions in movements and heart rate variation are caused by a temporary abolishment of the diurnal rhythm.16 Dexametasone has a less dramatic effect on fetal
behaviour, but there is evidence that the beneficial effects of this drug are less
than those of betametasone.
20
Numerous investigators have studied the effects of repeated fetal stimulation
mainly by using vibroacoustic stimulators (electro larynx, electric toothbrush or
other sound or vibratory sources). They looked at habituation, defined as the
progressive decrease in response when the fetus is stimulated repeatedly. This
process is considered a simple form of learning and is supposed to reflect normal brain functioning. However, the importance of habituation in distinguishing
between normal and abnormal fetuses is still controversial, mainly because there
39
10,34,44
Thus, this important topic still needs
Fetal movement patterns and behavioural states
281
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is no generally accepted standard procedure. Methodological differences among
the studies are abundant and include a multitude of sound sources, varying definitions as to habituation, absence of appropriate control episodes during which
no stimulation occurred, and neglect of the state dependency of fetal responses
to stimulation.
17,23,43
CONCLUSION
Fetal movements appear early, are specific from their inception and closely resemble movements after birth. This makes them candidates for diagnostic purposes.
Knowledge of normal fetal motor development and of fetal behavioural states is
important for the interpretation of other clinical measurements, such as fetal heart
rate records and Doppler velocity waveform patterns. Disturbances in embryonic
and fetal central nervous system development can be investigated by studying
the timetable of appearance of movement patterns, the quality of specific movements and the development of fetal behavioural states. Abnormal development
Ultrasound in obstetrics and gynaecology
can be found in many endogenous malfunctions and in disturbances caused by
maternal diseases and exogenous behavioural teratogens. It remains questionable
whether fetal behavioural studies will prove to be specific enough to identify the
individual fetus with impaired brain functioning, except in isolated cases.
282
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Normal gynaecological anatomy (uterus, tubes, ovaries)
Lil Valentin Povilas Sladkevicius
ABSTRACT
Ultrasound examination of the uterus and ovaries is best performed transvaginally.
The ultrasound morphology and size of the uterus and ovaries change during
the menstrual cycle. In menopausal transition the ovaries are smaller and contain
fewer follicles than during the reproductive years. They continue to shrink after
the menopause, when the uterus also becomes smaller. A small amount of fluid
in the pouch of Douglas is normal in women of fertile age but abnormal after
the menopause. Normal tubes can only be seen if they float freely in fluid in the
pouch of Douglas. On saline infusion sonography a normal uterine cavity is regular
and outlined by a smooth endometrium. Hystero-contrast salpingosonography is
used to assess tubal patency. If one can observe moving contrast in the interstitial
part of the tube for 10 seconds, and if no hydrosalpinx is seen, the tube is
probably patent, even if free spill of contrast around the ovary is not clearly seen.
KEYWORDS
Hydrosonography, hystero-contrast salpingosonography, menstrual cycle,
postmenopause, ultrasonography.
INTRODUCTION
Even though an ultrasound examination of the uterus and ovaries can be carried
out transabdominally, transvaginal ultrasound examination is preferable, because
it can be performed using higher ultrasound frequencies and this means better
resolution, which in turn means that very fine details can be seen. If transvaginal
ultrasound examination is impossible, transrectal ultrasound is an alternative.
The anterior–posterior diameter of the uterus should be measured from a sag-
ittal view of the uterus, where it appears to be at its thickest, and the width of the
285