Response of the premature fetus to stimulation by speech sounds.

The response of the premature fetus to speech stimuli was studied in 41 healthy pregnant patients at 26-34 weeks gestation. Speech stimuli consisted of repeated syllables ('ee' and 'ah') presented externally over the maternal abdomen at either 100, 105, or 110 decibels (dB). Sound stimuli were delivered during periods of both high and low fetal heart rate variability. During periods of low FHR variability, a decrease in fetal heart rate and an increase in the standard deviation of heart rate were found. During periods of high FHR variability, no significant change in either of these measures was observed. This is the first clear demonstration of heart rate responses to speech stimuli in the premature fetus. As is the case in the term fetus, this response is dependent on baseline heart rate variability which is the primary determinant of fetal state. The clinical usefulness of this finding may be limited by the magnitude of the response.

Patterns of development in fetal breathing activity in the latter third of gestation of the baboon.

Patterns of fetal breathing activity were examined in a longitudinal study of the fetal baboon over the latter third of gestation. More than 1400 h of recorded tracheal fluid pressure in 16 or 24 h records from seven fetuses over a range in gestation from 121 to 172 days (term, 175-180 days) were analyzed. In these 81 records, there was a high degree of variability in the percent of time spent breathing by the fetuses (range, 14-83%) with no apparent influence of gestational age (mean +/- S.D., 45.6 +/- 17.6%). Nonetheless, the mean amplitude of fetal breaths increased with gestation from absolute values of about 5-10 mmHg (r = 0.73, P < 0.001) and the mean inspiratory time interval increased from about 0.45-0.55 s (r = 0.40, P < 0.001). During epochs of breathing, the mean rate decreased from about 42-36 breaths per min (r = -0.54, P < 0.001) and the indices of both short term (r = -0.54, P < 0.001) and long term (r = -0.73, P < 0.001) variability in rate decreased. These results demonstrate a clearly defined pattern of development in the breathing activity of the fetal baboon which is comparable to the pattern described for the human fetus in the third trimester of gestation. These similarities suggest that the progressive functional maturation of the mechanisms generating respiratory patterns are comparable among primate species.

Time-trends in necropsy prevalence and birth prevalence of lung hypoplasia.

Congenital lung hypoplasia (LH) has been identified with increasing frequency in perinatal and neonatal necropsy reviews. The available prevalence figures have been derived using various diagnostic criteria in different populations and at various times. We therefore reviewed our experience in 15 years of consecutive early neonatal necropsies using one constant set of diagnostic criteria for LH and looked for a time-trend. We determined the necropsy prevalence (no. of cases of LH/no. of necropsies) and the birth prevalence (no. of cases of LH documented at necropsy per 1000 livebirths for inborn patients, and per 1000 referrals for outborn patients) between 1971 and 1985. We then divided this 15-year period into five consecutive 3-year periods to determine if a time-trend was discernible. Whereas early neonatal mortality for neonatal intensive care unit (NICU) admissions progressively decreased from 11.4% to 4.0% between the first and the last 3-year periods, the number of cases of LH per 3-year period did not vary appreciably. As a result, the prevalence of LH at necropsy showed a slight upward trend with time. The overall prevalence was 18%; it was 13% during the first and 23% during the last 3-year period. We found no time-trend in birth or referral prevalence for this lesion, which averaged 1.1 per 1000 livebirths and 9.8 per 1000 referrals. We conclude that lung hypoplasia appears to be emerging as an increasingly prevalent necropsy finding as a result of a shift in proportionate mortality, with the number of patients dying of other causes (denominator) decreasing, and the number of patients dying with lung hypoplasia remaining constant.

Method for processing of fetal breathing epoch analysis: studies in the primate.

An automated method for detecting fetal breathing and an analytic technique for providing significant data reduction that take the episodic nature of fetal breathing activity into account are described. The aim of the new technique, called epoch analysis, is to derive parameters of breathing and apnea that both summarize the activity and permit examination of its relationship to changes that occur naturally during day and night and with fetal maturation. The discussion covers: the acquisition of data from pregnant baboons; the breath detection process, for which a program was written; the recognition of breathing; computer recognition of artifacts; epoch characterization; validation of the methods of breath detection and epoch characterization; and application of the method. It is found that the technique has a broad capacity for data reduction and provides summaries of the activity that are amenable to analysis with standard statistical techniques.

Fetal breathing movements are not a reliable predictor of continued lung development in pregnancies complicated by oligohydramnios.

Fetal breathing activity was monitored by ultrasonography in 14 patients with oligohydramnios (4 with fetal anuria and 10 with premature rupture of the membranes). 45 patients with intact membranes, with normal amniotic fluid volume, and matched for gestational age were the controls. Fetal breathing movements were seen in all 8 patients who died in the perinatal period with a necropsy diagnosis of lung hypoplasia. While patients with premature rupture of the membranes (irrespective of outcome) spent the same or less time breathing than controls, fetuses with renal anomalies, oligohydramnios, and lung hypoplasia spent more time breathing than controls. The observation of fetal breathing activity is not helpful in identifying patients with oligohydramnios at risk of lung hypoplasia.

Oligohydramnios-induced lung hypoplasia: the influence of timing and duration in gestation.

We drained amniotic fluid for periods of 5 and 10 days at various times in gestation between days 40 and 55 in the guinea pig (term is 67 days). We analyzed the impact of this procedure on fetal lung growth and used untouched littermate fetuses as controls. During the canalicular stage of lung development, total lung DNA per gram of fetal weight was significantly reduced after only 5 days of oligohydramnios and the percent change did not vary between the two consecutive 5-day periods studied (period A, days 40 to 45, delta of -0.047 mg, p = 0.004; period B, days 45 to 50, delta of -0.042 mg, p = 0.002). The impact of the same duration of oligohydramnios on lung growth later in gestation, during the terminal sac stage of lung development, was less (period C, days 50 to 55, delta of -0.027 mg, p = 0.097). This reduction in effect between period A or B and C was significant at the 0.05 level using a one-way analysis of variance. Two overlapping 10-day periods were also studied. In both experiments, the percent changes in lung DNA per gram of fetal weight between experimental and littermate controls were significant (period D, days 40 to 50, delta of -0.072 mg, p = 0.001; period E, days 45 to 55, delta of -0.047 mg, p = 0.001). The inhibitory effect of oligohydramnios on lung growth was more marked in period D than E (significant at the 0.05 level).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of ultrasound in antenatal diagnosis of large-for-gestational age infants in diabetic gravid patients.

Near-term ultrasonograms of 44 diabetic gravid patients and 47 nondiabetic gravid patients were retrospectively analyzed. The mean values of abdominal diameter to femur length ratios and abdominal diameter to biparietal diameter ratios in diabetic gravid patients with large-for-gestational age fetuses were significantly different from those values in diabetic patients with appropriate-for-gestational age fetuses and in nondiabetic patients. Glycosylated hemoglobin values were above 7.4% (mean +/- 2 SD) in 79% of diabetic patients with large-for-gestational age infants and abdominal diameter to femur length ratio exceeding 1.385. Glycosylated hemoglobin values were less than or equal to 7.4% in 69% of diabetic gravid patients with appropriate-for-gestational age fetuses and abdominal diameter to femur length ratio less than 1.385. These findings suggest that large-for-gestational age infants have a different growth characteristic with a disproportionate enlargement of the abdomen. This possibly results from a long period of elevated levels of maternal plasma glucose (as shown by elevated values of glycosylated hemoglobin).

Optimized search for parameters useful in the interpretation of fetal heart rate data.

A comprehensive computerized perinatal data management system was used to acquire and process FHR data and to link this information to a set of control and outcome variable for 1000 deliveries. Multivariate correlation analyses and stepwise linear regression techniques were used to study the interrelationships between risk factors of pregnancy and labor, monitored data, obstetric interventions, and outcome. It was found that while some FHR characteristics, such as moderate-to-severe bradycardia, lack of beat-to-beat variability, and severe variable decelerations were significantly associated with poor outcome, others, such as accelerations, early decelerations, mild bradycardia, and mild-to-moderate tachycardia, were positively correlated with good outcome. Several statistical models for outcome prediction were developed using FHR data alone and also in conjunction with small subsets of control variables.