Baseline varibility on CTG is the oscillation of baseline FHR excluding acceleration and deceleration. A varibility of 5-25 BPM is a sign of fetal well-being. Decreased varibility is seen in:Fetal hypoxia Sleep apnoea Congenital malformation Maternal academia Infection Drugs given to mother such as sedatives, magnesim sulfphate, antihypertensivesWilliams 22/e, p 499: Drugs given to moter which decrease the baseline varibility are:Narcotics Barbiturates Phenothiazines Tranquilizers General anaesthetics Meperidine Butorphanol MgSO4According to Wiliams Increasing gestational age leads to increased baseline varibility, so it can be taken prematurity will have decreased varibility (i.e. option ‘b’ can be considered correct).