Association between congenital foot anomalies and gestational age at amniocentesis

OBJECTIVES

Our objectives were to confirm the reported association between early amniocentesis and congenital foot anomalies as well as to report, for the first time, on the outcome of amniocenteses performed during the 13th and 14th weeks of gestation.

METHODS

We conducted a triple cohort retrospective study of 4457 amniocenteses. Cohort definitions: early amniocentesis (EA), 11 weeks and 0/7 days to 12 weeks to 6/7 days; early midtrimester amniocentesis (EMA), 13 weeks and 0/7 days to 14 weeks and 6/7 days; and midtrimester amniocentesis (MA), 15 weeks and 0/7 days to 19 weeks and 6/7 days. Outcome measures were obtained by searching the Alberta Congenital Anomalies Surveillance System (ACASS) database for children born with foot anomalies represented by International Classification of Diseases version 9 (ICD-9) codes 754.5, 754.6 and 754.7.

RESULTS

Incidences of congenital foot anomalies were: EA 11/980 (1.1%), EMA 11/2515 (0.4%), and MA 1/962 (0.1%). There is a significant difference between the EA and EMA cohorts (p=0.019) and between the EA and MA cohorts (p=0.003); however, these data suggest there is no difference between EMA and MA cohorts (p=0.11).

CONCLUSIONS

Our incidence of congenital foot anomalies of 1.1% for women who underwent EA is similar to previously reported data, which further validates this association; however, our data also suggest that the foot anomaly risk may be limited to amniocenteses performed before the 13th week of gestation.

Evaluation of the twin peak or lambda sign in determining chorionicity in multiple pregnancy

OBJECTIVE

To assess prospectively the diagnostic capabilities of ultrasound assessment, using the twin peak or lambda sign, in determining chorionicity in multiple pregnancy.

METHODS

Fifty-five cases of multiple pregnancy were assessed. Real-time ultrasound scans of the origin of the inter-twin membrane for the presence or absence of the twin peak/lambda sign were performed and permanent images recorded. Chorionicity was determined by placental pathologic analysis.

RESULTS

Presence or absence of the twin peak/lambda sign as determined by real-time ultrasound correctly predicted chorionicity in 34 of 36 dichorionic and seven of eight monochorionic twin pregnancies: sensitivity for dichorionicity 94%, specificity 88%, positive predictive value 97%, and negative predictive value 78%. Real-time assessment was superior to analysis of permanent films.

CONCLUSION

Ultrasound assessment of chorionicity using the twin peak/lambda sign has high sensitivity and specificity, but accuracy may not be sufficient to guide clinical management in all cases.

The effect of glucose on Doppler flow velocity waveforms and heart rate pattern in the human fetus

Twenty-four healthy pregnant women were studied between 36 and 40 weeks gestation to determine the effect of glucose on the Doppler flow velocity waveform in the cerebral and umbilical arteries of the human fetus near term. The Resistance Index (RI), as an index of vascular resistance, was calculated for the anterior cerebral, internal carotid and umbilical arteries during a fasting control period, 45 min and again at 120 min after a 50-g maternal oral glucose drink or an equivalent amount of water. Fetal heart rate (FHR) pattern as determined by FHR variability was monitored as a measure of behavioural state. The RI of both cerebral vessels was significantly lower after the glucose drink, while that of the umbilical artery was little changed subsequent to either of the drinks. However the FHR mean min range, as an index of long term FHR variability was significantly increased when measured 30 to 60 min after the glucose drink and controlling for this change removed the effect of glucose on the RI of the cerebral vessels. We conclude that glucose does have an indirect effect on the cerebral Doppler waveform indices of the human fetus which is mediated through induced changes in behavioural state.

Perinatal assessment of cerebral flow velocity wave forms in the human fetus and neonate

The temporal relationship between changes in cerebral Doppler flow velocity wave forms, ductal patency, blood gases, and blood pressure during the transition from intrauterine to newborn life was assessed longitudinally in 16 healthy term fetuses and newborns. Doppler flow velocity wave forms were obtained from fetal cerebral arteries (anterior cerebral, internal carotid, and basilar) before birth, within 8 h after birth, and again at 24 and 48 h after birth. The resistance index was used as a measure of vascular resistance. The resistance index of the cerebral arteries studied increased significantly between the antenatal and 8-h study periods. This was followed by a significant decrease below fetal levels by the 24-h study period, with little change thereafter. We conclude that in the newborn human, as in the newborn lamb, the transition from fetal to immediate newborn life is associated with an increase in cerebral vascular resistance and thus a decrease in cerebral blood flow in response to the increase in arterial oxygenation. The subsequent decrease in the cerebral resistance index between 8 and 24 h of life cannot be explained by a loss of ductal shunting nor by associated changes in newborn blood gases or blood pressure, but may rather reflect a remodeling of the circulation due to impedance matching.

The effect of carbon dioxide on Doppler flow velocity waveforms in the human fetus

Twelve healthy pregnant women were studied between 35 to 40 weeks gestation to determine the effect of carbon dioxide on the Doppler flow velocity waveform in the cerebral and umbilical arteries of the human fetus near term. The Resistance index (RI), as an index of vascular resistance, was calculated for the internal carotid and umbilical arteries during a control period while patients breathed room air followed by three randomized 15-30 min study periods with patients breathing either room air, a prepared gas mixture with 2% carbon dioxide, or undergoing controlled hyperventilation as determined by monitoring end-tidal PCO2. The RI of the internal carotid and umbilical arteries both showed a significant inverse relationship to maternal end-tidal PCO2 with a greater negative slope for RI plotted against end-tidal PCO2 in the internal carotid artery (0.0153) than in the umbilical artery (0.0047). The change in the RI as an index of changing vascular resistance, suggests that carbon dioxide is also an important determinant of cerebral blood flow in the human fetus, as previously described for fetal sheep, with a lesser although significant effect on umbilical blood flow.

The interaction of behavioural state, heart rate and resistance index in the human fetus

The association and possible interactions of fetal behavioural state, fetal heart rate and vascular resistance was studied in 23 healthy pregnant women between 36 and 40 weeks' gestation. Doppler flow velocity waveforms were obtained from fetal cerebral (anterior cerebral, internal carotid and basilar), descending aorta and umbilical arteries during fetal behavioural state 1F and repeated during 2F. The Resistance Index (RI) was used as a measure of vascular resistance. Decreased vascular resistance was observed in all vessels except the umbilical artery during fetal behavioural state 2F compared to 1F (P less than 0.001). A significant interaction was observed between fetal heart rate and fetal behavioural state on the RI of the vessels studied, with a greater negative slope for RI plotted against fetal heart rate in fetal behavioural state 2F (-0.00139) compared to 1F (0.00005) (P less than 0.001). We conclude that the transition from fetal behavioural state 1F to 2F is associated with a significant reduction in cerebral and systemic vascular resistance, with no apparent change in placental resistance. Furthermore, fetal behavioural state and fetal heart rate interact, demonstrating a stronger association of fetal heart rate and RI in fetal behavioural state 2F in keeping with an increase in baroreflex sensitivity at this time.

Control of fetal breathing in the human fetus between 24 and 34 weeks' gestation

The effect of induced maternal hypocapnia and hypercapnia on fetal breathing movements was studied in 30 healthy pregnant women between 24 and 34 weeks' gestation to determine whether gestational age influences the fetal respiratory response to alterations in carbon dioxide levels. The percent time of fetal breathing movements correlated significantly with maternal end-tidal PCO2, increasing with maternal breathing of 2% and 4% carbon dioxide and decreasing with maternal hyperventilation for each of the three gestational age groups studied. However, the slope of this response for the 28- to 30-week group (3.29) and for the 32- to 34-week group (3.66), although similar to that of the term fetus, was significantly greater than that for the 24- to 26-week group (1.18, p less than 0.001). We conclude that the carbon dioxide level in the preterm fetus (as in the term fetus) is an important stimulus for the generation of respiratory movements. However, a developmental change is evident; the 24- to 26-week fetus demonstrates a decreased respiratory response to tonic carbon dioxide input. This may account for the decreased incidence of fetal breathing movements in the fetus of younger gestational age.

Patterns of fetal breathing activity in the human fetus at 24 to 28 weeks of gestation

Continuous 24-hour observations of fetal breathing were performed in 20 normal, pregnant women between 24 and 28 weeks' gestation by real-time ultrasound. Fetuses made breathing movements approximately 14% of the time. No change in breathing activity after a maternal meal was observed, but a significant increase in the incidence of fetal breathing activity was noted overnight. Fetuses at 24 to 28 weeks' gestation breathed at a rate of 44 breaths per minute, and the longest period of apnea noted was 14 minutes. These data suggest that the pattern and incidence of fetal breathing at 24 to 28 weeks' gestation are different from those of fetuses observed in the last 10 weeks of pregnancy. A maturational process in the control of fetal breathing may explain these observations.

Ultrasonic evaluation of fetal body movements over twenty-four hours in the human fetus at twenty-four to twenty-eight weeks' gestation

Continuous 24-hour observations of fetal gross body movements were performed in 20 women between 24 and 28 weeks of gestation by means of real-time ultrasound examination. At 24 to 26 weeks, fetuses moved 13.1% +/- 0.3% of the time, which was not significantly different from the incidence of 12.4% +/- 0.8% at 26 to 28 weeks' gestation. An examination of the number of movements per hour demonstrated that fetuses at 24 to 26 weeks' gestation moved on the average 53.4 +/- 1.6 times/hr, which was significantly different from 26 to 28 weeks' gestation when fetuses made 46.2 +/- 1.4 movements/hr. When examined on an hourly basis, fetuses in both age groups demonstrated a significant increase in the number of movements overnight from 2300 to 0800 hours. Intermovement intervals were also examined. Ninety-nine percent of intervals less than 6 minutes in both age groups contained movement. The longest observed quiescent interval was 24 minutes in both age groups. These data suggest that the incidence of fetal body movements is different than that observed in fetuses during the last 10 weeks of gestation. Fetuses at 24 to 28 weeks' gestation exhibit a diurnal pattern of fetal movement and move more frequently than do older fetuses. However, these movements are of a sporadic nature and relatively short duration. Thus these fetuses do not appear to have well-defined periods of rest and activity.

The role of carbon dioxide in the generation of human fetal breathing movements

To determine the role of carbon dioxide in the generation of fetal respiratory movements, the effect of induced maternal hypocapnia and hypercapnia on fetal breathing movements, gross body movements, and fetal heart rate was studied in 12 healthy pregnant women near term. Patients were studied for a 1-hour control period breathing room air followed by four randomized 15-minute study periods with patients breathing either room air, a prepared gas mixture with 2% or 4% carbon dioxide, or undergoing controlled hyperventilation as determined by monitoring end-tidal PCO2. The percentage of time fetal breathing movements correlated significantly with maternal end-tidal PCO2 (r = 0.62, p less than 0.01), increasing with maternal breathing of 2% and 4% carbon dioxide and decreasing with maternal hyperventilation. Fetal gross body movements, fetal heart rate, and fetal heart rate variability showed no significant changes. It is concluded that as in adults, the carbon dioxide level in fetuses is an important stimulus for the generation of respiratory movements, acting independent of a change in behavioral state. It is hypothesized that tonic carbon dioxide level input is an important determinant of fetal respiratory center drive, but little or no phasic carbon dioxide input exists because of continuous placental excretion, thus resulting in the episodic occurrence of breathing movements with changes in the fetal behavioral state.

Maternally perceived fetal activity from twenty-four weeks' gestation to term in normal and at risk pregnancies

Maternal perception of fetal activity was studied in normal and at risk pregnancies from 24 weeks' gestation until term in the second and third hour after a maternal meal. The trend for the median number of maternally perceived fetal movements in the 2-hour observation period, across gestation, was similar to that previously reported in both maternally perceived and ultrasound studies. The median number of perceived fetal movements in any 15-minute interval was similar for both groups and was constant over gestational age. The periodicity of fetal activity perceived by mothers correlated well with ultrasonic observations. The data support that fetal movement counts are very variable. Periodicity must be taken into account when maternally perceived fetal activity is used as a screen of fetal well-being. The data suggest that the patient should be observed for a consecutive period, up to a maximum of 2 hours. If no fetal activity is perceived by 2 consecutive hours of observation, then further evaluation of fetal well-being should be considered.

Strategies for developing a cost-effective pulmonary rehabilitation program

A cost-effective pulmonary rehabilitation program can be created by using strategic planning, a thorough budgetary process, and then promotion of the program. Strategic planning assesses the need for such a program, develops its overall direction, establishes priorities, assesses economic factors and the presence or absence of similar services already in existence, and identifies the proposed scope of the program. The budgetary process identifies the specific services to be offered and estimates the volume of services, their costs, and revenues. Promotion of the program serves to acquaint potential referring physicians and patients with the services to be offered. If preliminary investigation indicates that a pulmonary rehabilitation program is needed in the community, then strategic planning, careful budgeting, and creative promotion can help assure that the program is financially viable.