DOPPLER UMBILICAL FLOW WAVEFORMS IN MILD HYPERTENSIVE PREGNANCY

Objective: To assess the relationship between the Doppler umbilical artery flow velocity waveforms (AB ratio) in mild hypertensive pregnancy and the fetal outcome. Materials & Methods: This is prospective study which carried out between January 2004 and January 2005. Doppler examination of the umbilical artery was available for 135 pregnant women within 1 week of delivery. The value of the last Doppler AB ratio was classified into 3 groups: normal (AB ratio is <95th centile value) high AB ratio (if AB ratio is >95th but <99th centile value) and extreme AB ratio (if ratio is >99th centile value). Results: Normal AB ratio was found in 91% of mild hypertensive women and 82% of cases were delivered after 36 weeks with average mean birth weight and good Apgar score (more than 6 at one minute). Abnormal ratio was found in 5% of mild hypertensive cases with 40% of them was delivered before 36 weeks with significant admission in the intensive baby care unit. Conclusion: Doppler study can be used as a good tool for assessment of high risk fetus in mild hypertensive women. INTRODUCTION he use of Doppler ultrasound for the assessment of fetal and maternal blood flow is one of the more dramatic refinement in ultrasonic techniques in reproductive medicine with pulsed Doppler ultrasound guided by red-time imaging the so called duplex technique. It is possible to obtain flow signals from the second trimester on ward in the fetal great vessels and cardiac chambers and major abdominal and umbilical cord vessels, in addition to its use for evaluation of hemodynamics, the Doppler method has been used to estimate physiological quantities in the fetal and maternal circulation such as velocity, volumetric flow and pressure. There are two methods of estimating circulatory hemodynamics by direct measurement of the volume of blood flow and indirect estimation of flow velocity using waveform analysis, the last method might provide useful information about flow without engendering excessive errors. Indices have been developed to express this change in pattern and have been used as a measure of down stream resistance. There are three in common use, systolic-diastolic ratio (AB ratio), resistance index, pulsatility index. Doppler arterial waveforms in non pregnant women are characterized by high systolic velocity and little or no diastolic velocity, during pregnancy maternal and fetal vessels perfusing the placenta assume waveforms indicative of continuous diastolic flow. Doppler waveforms of vessels have been described in form of relationship between systole and diastole, these measurements are intended to relate peak flow at systole to that at end-diastole, and the ratio is calculated from the height of the systolic and diastolic peaks. Waveforms with a high flow in diastole accompany low down stream vessel impedance. In contrast, waveform with little diastolic flow or reversed flow are seen when vascular impedance down stream is abnormally high (e.g placental insufficiency and hypertension and retarded fetal growth. This study was undertaken to assess the relationship between the Doppler umbilical artery flow velocity waveforms (AB ratio) in mild hypertensive pregnancy and fetal outcome. MATERIAL AND METHODS Prospective study was carried during the period from January 2004 till January 2005 in Basrah Maternity and Child Hospital. The patients included in the study are pregnant women with history of mild hypertension (diastolic blood pressure > 90 mm Hg on at least 2 occasions with 6hrs apart and with patient at rest after 28 weeks with negative proteinurea. Patients were excluded from the study due to chronic hypertension or multiple pregnancy. The maternal characteristics features which were recorded include age, parity, gestational age (depend on the last menstrual period and early ultrasonic examination. The duration of hypertension was obtained from antenatal records (the gestational age at which the diastolic blood pressure measured > 90 mm Hg. The umbilical Doppler flow velocity waveforms (FVWs) were studied at weekly interval after T MJBU, VOL 25, No.2, 2007 40 admission until delivery. Doppler umbilical FVWs were recorded using a pulsed-wave Doppler system by the same personnel according to the following principles: FVWs should be recorded during periods of fetal inactivity. Both breathing and body movement alter the umbilical artery waveform. By insisting on fetal inactivity, possible variations due to an altered "state" are eliminated. It is necessary to view a sequence of 10-20 cardiac cycles (8-10 seconds) to establish that the fetus is not breathing and to ensure that the waveforms are constant. The shape of the umbilical artery waveforms is not altered by the site of recording along the cord except at its two extremes (very close to the fetal abdominal wall, and at the point of attachment of the umbilical cord to the placenta). Any variation because of these factors can be checked and eliminated by avoiding cord extremes and recording from at least two different points along it. Because of the coiling of the umbilical cord and its vessels, it is possible for the ultrasound beam to "sight" flow in the same direction in both the artery and the vein. This error can be eliminated by always checking the signal, by recording an arterial waveform with venous signal in the opposite direction. It is important that the maximum height of the flow waveform signal be recorded to ensure that the diastolic flow is not eliminated by high-pass filter. This is especially important when the diastolic component of the waveform is low. Waveforms should not be recorded during uterine contraction that might affect the flow pattern. The mother should be positioned to avoid supine hypotension. According to the normal range of the AB ratio, the values of AB ratios were classified to three groups: Normal AB ratio (if AB ratio is <95th centile value). High AB ratio (if AB ratio is ≥95th but <99th centile value). Extreme AB ratio (if AB ratio is ≥99th centile value). After delivery, the fetal outcome was recorded in terms of: Birth weight and centile weight for sex and age (confirmed postnatally by the maturity assessment table). Apgar Score at 1 and 5 min. Admission and duration of stay in the neonatal intensive care unit (NICU). Number of perinatal deaths. Statistical analysis Statistical differences between groups were determined using either a t-test or the Chisquare (χ2) test and analysis of variance (ANOVA). A level of 0.05 was required for significance. RESULTS During the period between January 2004 till January 2005, there were (135) pregnant women with mild hypertension without proteinurea were attending antenatal care in Maternity Hospital; 42(27.3%) were multiparous and 93(70.8%) were primigravidae. A Doppler umbilical artery flow velocity waveform relending was available for all the studied patients within 7 days of delivery. The mean interval between the last study and delivery was 1.7 days (SD.1.9). (Table-1) shows the distribution of the studied patients according to the Doppler umbilical artery AB ratio which is classified into three groups (normal, high and extreme). It shows that the majority of the studied patient with mild hypertension have normal Doppler umbilical artery AB ratio. Table 1. The distribution of the studied pregnant patients according to the Doppler umbilical artery