H.W. Jongsma

Intrapartum fetal pulse oximetry: fetal oxygen saturation trends during labor and relation to delivery outcome.

OBJECTIVES Our purpose was to study fetal arterial oxygen saturation trends by continuous pulse oximetry during labor in subjects with normal and abnormal delivery outcomes. STUDY DESIGN Continuous fetal arterial oxygen saturation was measured during labor with a noninvasive reflectance pulse oximeter designed for fetal application. Averaged arterial oxygen saturation values were compared between stage 1 and stage 2 of labor, with stage 1 further subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases. Delivery outcome was considered to be abnormal for any of the following conditions: gestational age < 37 weeks, maternal oxygen administration, delivery by cesarean section, 5-minute Apgar score < 7, umbilical artery pH < 7.10, birth weight < 2500 gm, or newborn intensive care unit admission. RESULTS A total of 291 subjects were studied: 142 in Provo, 90 in Nijmegen and 59 in San Francisco. Subjects with delivery complications (n = 125) were evaluated separately from those with normal delivery outcomes (n = 160). Fetal arterial oxygen saturation was 58% +/- 10% (mean +/- SD) during the cumulative period of study for the normal-outcome group. A significant decrease (paired t test, p < 0.001) in fetal arterial oxygen saturation occurred from stage 1 (59% +/- 10%) to stage 2 (53% +/- 10%) labor. When stage 1 was subdivided into early (< or = 4 cm), middle (5 to 7 cm), and late (8 to 10 cm) phases, a gradual decreasing trend in fetal arterial oxygen saturation was observed: 62% +/- 9%, 60% +/- 11%, and 58% +/- 10%. CONCLUSIONS With the use of reflectance pulse oximetry, a statistically significant decrease in fetal arterial oxygen saturation was observed during labor in women with normal and abnormal delivery outcomes.

Computer analysis of antepartum fetal heart rate: 1. Baseline determination

A consequent and reproducible determination of baseline is an essential prerequisite for objective interpretation of fetal heart rate. A fully automated off-line method of baseline determination has been developed and tested on 50 normal antepartum fetal heart rate recordings of two hours duration. The method is constructed around two functional units, a digital filter and a trim function, which interact in an iterative process. The results were evaluated in comparison with automated baseline determination according to Dawes and coworkers. A panel of 3 experts agreed that in 14 of the 50 recordings (28%), the new developed procedure resulted in a substantially better baseline fit. In the remaining 34 recordings (72%), baseline fit from both methods was judged as equivalent. The described procedure of baseline determination provides a solid base for automated detection of accelerations and decelerations in fetal heart rate recordings. It enables the study of the relation between the fetal heart rate pattern and fetal movements. Finally, it provides an objective tool for analysis of variables within the fetal heart rate with the highest predictive value with respect to fetal outcome.

Percentiles for gas values in human umbilical cord blood

The distribution of gas values of umbilical cord blood was studied in an university clinic population during a period of 3 yr. All patients in labor were guided by obstetrical personnel and continuous electronic fetal monitoring (CTG). Microblood analyses were performed on indication of the CTG. The tenth percentile for the total population for umbilical artery blood pH was 7.14 and base excess was -12.7 mmol/l. The tenth percentile for pH in umbilical venous blood was 7.23 and base excess was -10.2 mmol/l. Increase of acidemia was seen in the following order: optimal pregnancy and labor, spontaneous vertex delivery, multiparity, primiparity, instrumental and breech delivery. Percentiles of umbilical cord blood gases could serve as an index for the standard of obstetrical care in addition to perinatal mortality and other measures of perinatal morbidity.

Mechanisms of late decelerations in the fetal heart rate. A study with autonomic blocking agents in fetal lambs.

Fetal heart rate decelerations resembling the late deceleration FHR pattern were produced in fetal sheep by periodic occlusion of the maternal common hypogastric artery for 30-60 sec. Transient fetal hypertension also occurred during the occlusions. Alpha-adrenergic blockade with phentolamine eliminated or markedly reduced the hypertensive response. FHR decelerations still occurred intermittently with some occlusions; however, their character was greatly altered. After parasympathetic blockade with atropine, the decelerations were replaced by periodic FHR accelerations during the occlusions. These accelerations were, in turn, eliminated by the beta-adrenergic blocking agent, propranolol. In the presence of combined parasympathetic, alpha- and beta-adrenergic blockade, the FHR remained essentially constant during the hypogastric artery occlusions in non-acidemic fetuses. FHR decelerations persisted after parasympathetic or total autonomic blockade when the fetuses were significantly hypoxic, as judged by depressed arterial blood pH and base excess values. Beat-to-beat variability of the baseline FHR persisted in the face of severe hypoxia and acidosis. These observations demonstrate that reflex mechanisms are involved importantly in the genesis of late deceleration FHR patterns in the acutely hypoxemic fetus, but that direct depression of myocardial rhythmicity becomes a factor as hypoxic acidosis develops.

Analysis of heart rate and beat-to-beat variability: Interval difference index

The relationshp between the RR interval length (RR) and the RR interval-to-interval differences (RR differences) was investigated. Data on heart rate were obtained from 11 newborn infants in well-defined behavioral states undergoing polygraphy. It was found that the RR differences were strongly dependent on the RR interval length in all behavioral states. The relationship between the RR differences (y) and the interval length (RR) could be described by the equation y = alpha (RR-320)1.5 for the interval length in the investigated range from 375 to 605 msec. On the basis of this relationship the interval difference index (ID index) was constructed for the quantification of beat-to-beat heart rate variability. The ID index showed good independence from the long-term irregularity index (LTI index). Other statistical parameters proposed for the quantification of beat-to-beat heart rate variability are discussed and compared with the ID index.

The rhythmicity of fetal breathing varies with behavioural state in the human fetus

The rhythmicity of human fetal breathing movements was studied during two different behavioural states (1F and 2F, respectively), using real-time B-scan-directed M-mode ultrasound recordings. The mean breath-to-breath interval durations and the standard deviations (SD), and the standard deviations of the interval differences (SDDSI) were calculated. The mean breath-to-breath interval duration was not significantly shorter during 1F than during 2F. SD and SDDSI, however, showed significantly lower values during 1F, demonstrating that the fetal breathing rhythm is more regular during state 1F than during state 2F epochs. Regular fetal breathing is thus a concomitant of state 1F.

Heart rate as an indicator of the behavioral state: Studies in the newborn infant and prospects for fetal heart rate monitoring☆☆☆

Term healthy newborn infants underwent polygraphy between days 4 and 6 of life. Behavioral states were determined according to Prechtls criteria. The neonatal heart rate was analyzed for the various behavioral states, with the use of quantitative indices for long-term and short-term irregularity. The applied indices were, respectively, the long-term irregularity index (LTI index) and the interval difference index (ID index). During state 1 the R-R interval length was longer (p less than 0.01), the LTI index lower (p less than 0.01), and the ID index higher (p less then 0.02) than in the immediately preceding or following state 2. For nonconsecutive states 1 and 2 a maximum separation was obtained with the discriminant function 0.0159 RR - 0.065 LTI + 0.062 ID - 7.49. This discriminant function gave a total percentage of correct classification of states 1 and 2 epochs of 93%. The data are discussed with respect to the presence of cycling sleep states in the newborn infant as well as in the fetus. Prospects for fetal antepartum heart rate monitoring are considered.

The umbilical artery blood flow velocity waveform in relation to fetal breathing movements, fetal heart rate and fetal behavioural states in normal pregnancy at 37 to 39 weeks

In 19 normal pregnancies between 37 and 39 weeks of gestation, the blood flow velocity waveform (FVW) of the umbilical artery was studied in relation to fetal breathing movements, fetal heart rate (FHR) and the fetal heart rate patterns (FHRPs) A and B. FHRP A is stable, with a narrow oscillation bandwidth, FHRP B shows a wider oscillation bandwidth. Although for state-assessment it is necessary to record three variables simultaneously, the linkage of these variables in the near-term healthy fetus is such, that FHRP A and B may be used for the assignment of behavioural states 1F and 2F. The FVW was characterized by the Pulsatility-Index (PI). Presence of fetal breathing movements strongly disturbed the regularity of the FVW. A significant inverse relationship between FHR and PI was established. A weighted regression coefficient was calculated: PI decreases 0.0075 with an increase of FHR of 1 beat per minute (PI140 = PI / 0.0075(FHR - 140]. The PI was higher during periods of FHRP A as compared to FHRP B. However, this difference disappeared, when the influence of FHR was taken into account by normalising all PIs to a standard heart rate level of 140 bpm. One should perform the umbilical artery blood flow measurements in absence of fetal breathing--(causing irregularity of the FVW) and body movements (because of accompanying FHR accelerations) and FHR should be taken into account when evaluating the FVWs.

Effects of maternal glucose ingestion on human fetal breathing movements at weeks 24 and 28 of gestation

The incidence of human fetal breathing movements was studied in normal pregnancies before and after administration of 50 g glucose or a placebo (water) at 24 and 28 weeks. Glucose or water was given to the same women on two separate days in a randomised order. No significant differences were present among the results on the placebo-day and the control period of the glucose-day at either gestational age. On the glucose-day, the incidence rose significantly from 3.6 to a maximum of 11.6% at 24 weeks, and from 6.7 to 30.2% at 28 weeks. At both ages the maximum was found 90-120 min after the intake of glucose. It is concluded that already at 24 weeks gestation the human fetus reacts with an increase of fetal breathing movements after the administration of glucose to the mother.

The accuracy of ultrasonic measurement of fetal crown-rump length

Routine ultrasonic crown-rump length measurements were retrospectively evaluated in an antenatal clinic using maternal body temperature graphs as reference to ovulatory age. A comparison with the original figures of Robinson is made. Potential errors are discussed. The conclusion is that one should be very careful in interpreting an ultrasonic CRL measurement before 10 weeks menstrual age because of both measurement and operator errors.