ULTRASOUND MEASUREMENT OF FETAL ADRENAL GLAND VOLUME IN PREDICTING SPONTANEOUS ONSET OF LABOUR . Section Original Research Paper

Abstract

BACKGROUND: The Placental clock plays a pivotal role in interrupting the uterine quiescence and leads to onset of labor^(1,2). Biochemical activation causes increased dehydro-epiandrostenedione sulfate production in central zone of fetal adrenal gland. Hence fetal adrenal zone and adrenal gland increase in size This imparts a clue that fetal adrenal gland measurement in pregnancy can be  used as a non invasive marker for onset of labor and hence found to be useful in predicting preterm labor^(3,4). ⁽⁴⁾.Dimensions of fetal adrenal gland and fetal adrenal zone increase with increasing gestation age as part of physiological development. However despite this increase, proportion of gland occupied by fetal zone remains constant throughout gestation in all dimensions. This facilitates the distinction between an abnormal hypertrophy of fetal zone and a physiologic increase in its size that is in linear relationship with remainder  of gland⁽⁴⁾. More number of women are interested in prediction of spontaneous onset of labour even at term. In recent scenario cervical assessment is used for same. In our study we hypothesise that fetal adrenal gland volume and adrenal zone parameters can predict preterm and term labor with same efficacy. METHODOLOGY: A prospective observational cohort study with low risk pregnant women is conducted. The subjects underwent a detailed clinical examination. Apart from routine investigations, they were assessed for corrected fetal adrenal gland volume, fetal adrenal zone parameters including fetal adrenal zone width ratio and zone depth ratio and cervical length at 28 to 34 weeks period of gestation. Corrected fetal adrenal gland volume and adrenal zone parameters was assessed again at 37 to 39 weeks period of gestation. Data is recorded in specially designed proforma and then transferred to master sheet. SUMMARY: In a prospective study conducted in KGH, with a 100 sample size, majority of patients were primigravida, less than 25yrs.A significant correlation was found between increased fetal adrenal gland and fetal adrenal zone enlargement in those who delivered preterm. Enlarged fetal adrenal gland volume of 331 mm3/kg and enlarged fetal width ratio are an excellent predictor of preterm delivery in this study when compared to depth ratio and cervical length. Also this study found that fetal adrenal gland volume enlargement can predict the occurrence of spontaneous labour. On followup scan at term gestation of 37 to 39 weeks, spontaneous labour group had more adrenal gland volume when compared to those who had to be induced. CONCLUSION: The concept that the fetus contributes to the start of parturition is the basis for the usage of fetal adrenal gland volume and fetal adrenal zone enlargement to forecast the likely occurrence of preterm birth and also to predict the spontaneous onset of labour at term. The same has been showed in this study where women who delivered preterm and in those who had spontaneous term labour had increased fetal adrenal gland volume and fetal adrenal zone enlargement. It would be helpful in incorporating fetal adrenal gland volume in our regular follow-ups.In those with threatened preterm and enlarged fetal adrenal gland we can avoid unnecessary intervention like cervical encirclage or tocolysis and such women can be given antenatal steroids and referred to a tertiary center with NICU and SNCU care. In modern obstetrics, the establishment of a day-by-day predictable cutoffs would provide fetal adrenal glands a new role in the prediction of labour  (term or  preterm).  In all  women prior  to induction of  labour,  we can consider  AGV as a  a  part  of  routine ultrasonography to predict successful induction of labour. This sort of predictability not only will offer the obstetrician time to efficiently employ resources but also will provide the parturient and her family a clarity of plan.

Keywords: FETAL ADRENAL GLAND VOLUME