Influence of gestational age and fetal heart rate on the fetal mechanical PR interval.

OBJECTIVE: The fetal mechanical PR interval obtained via pulsed Doppler has previously been demonstrated to correlate with electrocardiographic PR interval measured in the neonate. We sought to further analyze the influence of fetal heart rate and gestational age upon the fetal mechanical PR interval. METHODS: We searched our database for mechanical PR intervals, which were obtained during fetal echocardiography performed in our antenatal diagnostic unit. We included fetuses with a normal cardiac structural survey. The mechanical PR interval is measured from the A wave of the mitral valve to the beginning of ventricular systole corresponding to the opening of the aortic valve. Linear regression curves were generated to examine the correlation of mechanical PR interval with gestational age and fetal heart rate. Analysis of variance was used to compare the mean variation across three gestational age groups: 17-21.9 weeks (n = 24), 22-25.9 weeks (n = 52) and 26-38 weeks (n = 20). RESULTS: Mechanical PR intervals were measured in 96 fetuses with normal fetal echocardiography. The mechanical PR interval was 123.9 +/- 10.3 ms (mean +/- SD), with a range of 90-150 ms. Linear regression curves correlating mechanical PR interval with fetal heart rate and gestational age demonstrated a flat slope with R2 = 0.016, p = 0.22 and R2 = 0.0004, p = 0.85, respectively. The mechanical PR interval measured over the three gestational ages was as follows (mean +/- SD): 122.3 +/- 10.5 ms for 17-21.9 weeks; 125.0 +/- 9.6 ms for 22-25.9 weeks; and 123.1 +/- 11.9 ms for 26-38 weeks. Analysis of variance revealed no difference among the mechanical PR interval means measured over the three gestational age groups (p = 0.53). CONCLUSIONS: Fetal mechanical PR interval ranges from 90 to 150 ms in fetuses with sonographically normal fetal cardiac structure and rate. The mechanical PR interval appears to be independent of gestational age and fetal heart rate.     

Abnormal fetal heart rate patterns during the active phase of labor: the value of fetal oxygen saturation

Objective: To determine the predictive value of intrapartum fetal oxygen saturation (SO₂) for prediction of an umbilical artery pH less than 7.15 at birth in labors complicated by abnormal fetal heart rate traces. Study design: Eighty-five primigravidas in spontaneous labor complicated by abnormal fetal heart rate traces underwent fetal SO₂ monitoring using the fetal pulse oximetry technique. Cases with an SO₂ of < 30% were delivered by Cesarean section. Umbilical artery pH was measured at birth in all women. Results: With the value set of 30% as the cut-off point of fetal oxygen saturation, the positive predictive value for umbilical artery pH of < 7.15 was 61.5% and the negative predictive value was 95.8%, with a sensitivity of 72% and a specificity of 93%. Conclusions: Fetal pulse oximetry is a promising technique for assessment of fetal well-being during labor and may decrease the number of unnecessary Cesarean sections.     

Relationship of baseline fetal heart rate to gestational age and fetal sex

A study of 37 patients who underwent 365 antepartum fetal heart rate tests showed a significant difference in heart rate between 19 to 24 weeks' and 36 to 40 weeks' gestation. Baseline heart rate remained within the normal range, suggesting that an abnormal heart rate at any gestational age should prompt further fetal assessment. Baseline fetal heart rate was not significantly different between male and female fetuses.     

The effect of age on the ovarian response to gonadotropin and on pregnancy rate in polycystic ovary syndrome

Recent studies have proposed that ,in women affected by the polycystic ovary syndrome (PCOS) ,aging is able to regularize the menstrual cyclicity. To evaluate the ovarian response in PCOS patients according to their age ,we studied 33 PCOS patients ,20 of whom with an age ranging from 28 to 34 years (younger PCOS) and 13 ranging from 35 to 45 years (older PCOS). All patients underwent an ovulation induction therapeutic protocol with low-dose recombinant follicle stimulating hormone ,for a total of 80 cycles (44 cycles for the younger PCOS group and 36 cycles for the older PCOS group). No significant difference was found between the days of therapy (12.3 ± 5.4 vs. 13.5 ± 5.6 days) ,total amount of drugs (980.7 ± 568.9 IU vs. 1063.9 ± 469.5 IU) or ovulation rate (93% vs. 89%) in the two groups. The two groups showed a significant difference in the maximum estradiol level (2053.5 ± 1497.2 vs. 1269.0 ± 911.5 pmol/l ,p < 0.01) ,the number of the recruited and preovulatory follicles (1.7 ± 2.5 vs. 0.64 ± 0.9 ,p < 0.05 and 1.7 ± 1.1 vs. 1.2 ± 0.5 ,p < 0.01 ,respectively) and the pregnancy rate (36% vs. 14% ,p < 0.05). In conclusion ,our data clearly showed that ,also in PCOS ,advanced age is a negative prognostic factor in the ovarian response to ovulation induction therapies.     

Computerized analysis of fetal heart rate parameters by gestational age.

OBJECTIVE: The aim of this study is to define the reference ranges for fetal heart rate (FHR) parameters according to gestational age, by determining the relationship between the FHR and gestational age using a computerized FHR analysis system. METHODS: Using our own software developed by Hanyang University Hospital in Korea, non-stress tests were performed for 20 min. FHR parameters for 6455 subjects were analyzed for various gestational groups; <25 weeks, 25-28 weeks, 29-32 weeks, 33-36 weeks, 37-40 weeks, and >40 weeks. RESULTS: The FHR parameters were related to gestational age. The mean baseline FHR, signal loss, and fetal movements decreased significantly with gestation (P<0.0001). The variability and accelerations of FHR were highest for the 37-40 weeks gestational group (P<0.05). CONCLUSIONS: The results showed that overall, the differences in the FHR parameters between gestational groups were statistically significant, and the gestational age of the fetus should be considered when interpreting FHR patterns.     

Effect of gestational age on baseline fetal heart rate during the third trimester of pregnancy

Analysis of the fetal heart rate in 3,127 reactive nonstress tests revealed that the baseline rate decreased significantly between 28 and 41 weeks' gestation (6.4 beats per minute [4.5%]). Analysis of 235 women with two tests at least four weeks apart revealed that while the majority (51.1%) demonstrated a decrease, 26.8% experienced a rise in the baseline rate during the testing interval.     

Comparison of the accuracy of gestational age estimation from fetal heart rate and crown-rump length

Objective: To compare the accuracy of gestational age (GA) estimation predicted by fetal heart rate (FHR) versus crown-rump length (CRL) measurements in early pregnancies.Methods: A total of 145 infertile women with singleton intrauterine pregnancies conceived through in vitro fertilization underwent vaginal ultrasonographic examination in early stage of pregnancy. We performed 197 FHR and 398 CRL measurements. The relationship between GA (counted with the day of oocyte retrieval used as day 14) and the FHR or CRL was explored with regression analysis by means of least squares. Polynomials up to the third order were analyzed, and the coefficient of determination (R²) was calculated.Results: Fetal cardiac activity could be detected as early as 38 days, gradually increased to 188 beats per minute at 62 days of gestation. Regression analysis with GA as dependent variable resulted in R² values of 0.906, 0.907, and 0.908 for the first, second, and third order polynomials, respectively. The standard deviations around the regression line were 2.90, 2.81, and 2.84 days, respectively. The second order polynomial to describe GA (days) estimated by FHR (beats per min): GA = 3.02E-41FHR² + 1.60E-11FHR + 2.22E+1. On the other hand, the CRL was measured at 38 days to 62 days of gestation. Regression analysis resulted in R² values of 0.827, 0.839, and 0.841, respectively. The deviations were 4.11, 3.83, and 3.89 days, respectively. The second order polynomial to describe GA estimated by CRL (mm): GA = −2.10E-21CRL² + 1.49E+01CRL + 3.86E+1. There was no difference between the R² values and no difference between the standard deviations around the regression lines.Conclusion: Our results indicate no statistically significant difference in the accuracy of GA estimation predicted by FHR versus CRL measurements. But better mathematical fits were obtained when the data of FHR were used for GA estimation. These findings suggest that the FHR measurement may be a new method for early ultrasound dating. This study mentions for the first time the possibility of “FHR dating” with functional data.     

The distribution of accelerations of the human fetal heart rate at 38 to 40 weeks' gestational age

In order to further understand the use of antepartum fetal heart rate monitoring we measured the distribution, in time, of two, three, or five fetal heart rate accelerations of greater than or equal to 15 bpm for greater than or equal to 15 seconds and of greater than or equal to 10 bpm for greater than or equal to 6 seconds in 12 healthy pregnant women at 38 to 40 weeks' gestation. The length of time necessary to measure 50% or 95% of intervals containing five accelerations would be substantially reduced by changing to a definition of two or three accelerations. However, an observation interval of at least 80 minutes is required to include the longest time interval of two, three, or five accelerations. These data may suggest new strategies for decreasing time and expense of fetal heart rate testing.     

A prospective analysis of the influence of gestational age on the baseline fetal heart rate and reactivity in a low-risk population

The nonstress test is of recognized value for the antepartum assessment of fetal well-being. Less well defined, however, is the relationship between baseline fetal heart rate, reactivity, and the gestational age of the fetus. A prospective analysis of the nonstress test in a preterm, low-risk population was begun. Weekly tests were begun as early as 23 weeks and continued to term. A test was considered reactive if there were two or more fetal heart rate accelerations within a 20-minute period. A total of 128 nonstress tests were performed on 25 low-risk patients. Of these tests, 84 (64%) were considered reactive. With advancing gestational age, a progressive increase in the incidence of reactive tests was observed. However, no significant difference in baseline fetal heart rate could be identified between term and preterm fetuses. In addition, the frequency and amount of accelerations and decelerations were determined. Decelerations were not noted more frequently in the preterm population. Conversely, accelerations occurred more frequently with advancing gestational age. The pregnancy outcome was excellent for all study patients. It is concluded, therefore, that with advancing gestational age more reactive nonstress tests are seen. Baseline fetal heart rate and the frequency of decelerations appear to be unaffected by advancing gestational age. Finally, although the numbers are small, the nonstress test appears to be a suitable technique for assessing fetal well-being in the preterm fetus.     

小于胎龄早产儿产时胎心电子监护图形特征及其临床意义

目的探讨小于胎龄早产儿胎心电子监护图形(CTG)特征及其临床意义。方法回顾性分析303例32~36孕周、无妊娠合并症的单纯胎膜早破和原因不明早产孕妇的全产程CTG。其中,小于胎龄早产儿78例(PSGA组),适于胎龄早产儿225例(PAGA组)。比较宫缩时两组CTG特征,合并症情况及分娩结局。结果PSGA组及PAGA组出现单纯U型变异减速的胎儿分别为24例(308%)和10例(44%),两组比较,差异有统计学意义(P<001);U型变异减速合并其他异常CTG的胎儿分别为10例(128%)和1例(04%),两组比较,差异也有统计学意义(P<001)。PSGA组,出现单纯U型变异减速者的难产率(208%)与胎心电子监护无异常者的难产率(227%)比较,差异无统计学意义(P>005),但与U型变异减速合并其他异常CTG者的难产率(600%)比较,差异有统计学意义(P<005)。PSGA组中,34例出现U形变异减速,其中合并脐带异常15例(绕颈、绕身14例、脐带过短1例),PSGA组44例无U形变异减速者中,合并脐带异常9例(绕颈、绕身),两组比较,差异有统计学意义(P<005)。结论U形变异减速是小于胎龄早产儿分娩过程中的特征性胎儿监护图形,但不是胎儿缺氧的征象,如不合并其他异常CTG,不需特殊处理。     

Fetal heart rate and fetal activity patterns after vibratory acoustic stimulation at thirty to thirty-two weeks' gestational age

Twenty pregnant women between 30 and 32 weeks' gestational age were studied to examine the effects of a 5-second external vibratory acoustic stimulus on the fetal heart rate, fetal heart rate variability, and fetal activity patterns. There was an immediate significant increase in the basal fetal heart rate for 10 minutes compared with controls. There was also a significant increase in the mean duration of fetal heart rate accelerations without any change in the number of fetal heart rate accelerations. There were no changes in long-term fetal heart rate variability, fetal breathing, and gross fetal body movements.     

The relationship between gestational weeks and fetal breathing movements in each pattern of the fetal heart rate

Fetal breathing movement (FBM) was analysed in each fetal heart rate (FHR) pattern and the gestational 2 weeks. FHR pattern was divided in automated FHR analysis into 3 groups; active, intermediate and resting patterns. The patients consisted of 102 pregnant women at 30-41 weeks, including 13 complicated pregnancies. 1) The active pattern percentage was 52.7% at 32-33 weeks and it decreased gradually. That of the resting pattern was 25.5% at 32-33 weeks and it increased gradually. 2) The percentages of positive FBM in the active pattern were significantly larger than those in the resting pattern in each 2 weeks. 3) The duration of continuous FBM ranged from 3 to 202 sec. FBM of long duration tended to exist in the resting pattern rather than in the active pattern. 4) The percent time ratio of FBM ranged from 1.0 to 92.7% and showed no definite relationship with the FHR patterns or gestational weeks. 5) The FBM rates in each FHR pattern showed no significant differences. Their sequential differences after 36 weeks were significant; that is, FBM in the resting pattern was more regular than that in the active pattern. 6) In high risk pregnancy, the resting pattern percentage was 52.3% and the ratio of positive FBM in the resting pattern was significantly smaller than that in active pattern.     

Influence of gestational age on fetal deoxyribonucleic acid retrieval in maternal peripheral blood

OBJECTIVE: We wanted to verify whether gestational age influences the retrieval of fetal deoxyribonucleic acid in maternal blood to identify the best period for maternal blood sampling for a future noninvasive prenatal diagnoses. STUDY DESIGN: We amplified 81 deoxyribonucleic acid samples extracted from the peripheral blood of 27 pregnant women (18 bearing male fetuses and 9 bearing females) by nested polymerase chain reaction of the Y-specific sequence DYS14. We obtained three blood samples (one per gestational trimester) from each woman. Statistical evaluation was assessed by the McNemar test of symmetry. RESULTS: Polymerase chain reaction results in male-bearing pregnancies differed significantly between the first and second trimesters and between the second and third trimesters (p < 0.025) in parallel with a decrease in sensitivity in the second trimester (67%) compared with the first (94%) and third trimesters (100%). CONCLUSIONS: The drop in sensitivity from the first to the second trimester witnesses a variable concentration of fetal cells in maternal blood, with a negative balance in the second trimester. Therefore, to achieve an adequate polymerase chain reaction accuracy, the choice of gestational age is relevant and the first trimester seems to be more suitable than the second trimester.(Am J Obstet Gynecol 1997;177:22)     

Influence of gestational age on prediction of fetal lung maturity by fluorescence polarization of amniotic fluid

Compared are the amniotic fluid fluorescence polarization values and the neonatal outcomes of 201 pregnant women who delivered from 28 through 37 weeks of gestation within 48 hours of the fluorescence polarization determinations. Thirty-five neonates developed hyaline membrane disease. The corresponding fluorescence polarization values ranged from 0.275 to 0.391. Eight of those 35 tests results were less than 0.325. The predictiveness of the method was studied using different threshold fluorescence polarization values. At the authors' own threshold of less than or equal to 0.325, the overall predictive value was as follows: false mature predictions: 6.2%, false immature predictions: 62.5%, sensitivity: 77.1%, and specificity: 72.8%. However, the false mature prediction rate was 21 to 40% from week 28 through week 33 versus 3.4 to 5.8% from week 34 through week 37, depending on the selected cutoff fluorescence polarization value. The sensitivity and specificity before, at, or after week 34 were significantly different at all tested fluorescence polarization values (P less than .05 to P less than .01) with the exception of the sensitivity at 0.310 and at 0.316 (P = .057). Caution is advised against relying on the fluorescence polarization method to predict fetal lung maturity at least before 34 weeks of gestation.