Nonstress test in high-risk pregnancy: Evaluation and Management

Evaluation of nonstress test (NST) in the antenatal assessment of fetal well being in the high-risk pregnancy has been found to be clinically efficacious. The basis for its interpretation has been the reactive or normal and no reactive or abnormal test. Between January 1997 and May 1998, 53 high risk pregnant women were studied by NST at the Department of Obstetrics and Gynaecology, Bangabandhu Sheikh Mujib Medical University. Reactive group showed favourable fetal outcome and no reactive showed significant increase in overall abnormal outcome, low 1and 5minute apgar score, small for gestational age infants subsequently admission into neonatal care unit and perinatal mortality. Based on our experience, the NST continue to be a valuable procedure for the assessment of fetal well being in our high risk pregnancies. Introduction The antepartum assessment of fetal well being has become an integral part of the management of any high risk pregnancy. In order to achieve this evaluation, varying biochemical and biophysical techniques have been described. The biophysical techniques, primarily the antepartum fetal heart rate testing (AFHRT) have enabled the clinician to immediately and reliably evaluate fetal status. There is relationship between fetal movement and heart rate acceleration demonstrated by Rochard et al and Lee et al. They demonstrated acceleration of foetal heart rate associated with fetal movement in Rh isoimmunized babies where no stress factor was applied. Evertson et al demonstrated from several retrospective studies of potential for nonstress test (NST) and clearly defined repetitive acceleration and the absence of positive contraction stress test (CST) result. Therefore, NST may be defined as acceleration of fetal heart rate (FHR) in association with fetal movement when no external stress is applied. Twenty one different standards for reactive NST showed that the most common criteria for reactivity was the presence of at least two times fetal heart rate acceleration of at least 15 cpm amplitude and of 15 second duration in any 20minute epoch. Mostly used other interpretive criteria and correlation between NST and diagnostic parameters, e.g-sensitivity, specification, etc. The interval between tests was originally set 7day interval have shortened as experience evolved and performed twice weekly or often daily or even more frequently. According to fetal sleep wake cycle as described by Pillai and James, 40 minute testing time is standard for NST. Continuous experience showed some limitations of CST. The main problems were the length of time required, 6090 minutes, needed for intervening access usually hospital based, high incidence of suspicious or equivocal result, lack of specificity of positive result. 1. Dr. Mahfuz Ara Begum, MBBS, MCPS, DGO, FCPS, MS (Gyn), Registrar (Obstetrics and Gynaecology), Sir salimullah Medical College and Mitford Hospital, Dhaka. 2. Dr. Shahla Khatun, FRCOG, RCS, Ex Professor and Chairperson, Department of Obstetrics and Gynaecology, Bangabandhu Sheikh Mujib Medical University, Dhaka