This chapter discusses the key implications, diagnostic signs and management techniques for fluid overload and underload during pregnancy. Pulmonary oedema, although uncommon in pregnancy, is associated with an increase in maternal and fetal morbidity and mortality. Inadequate plasma volume expansion in pregnancy is linked to poor fetal outcome. Volume loss due to hyperemesis gravidarum or haemorrhage can lead to maternal hypotension, collapse and fetal distress due to poor placental perfusion. Hypoxia and radiological signs of pulmonary oedema in chest X-ray are some diagnostic signs. Management for fluid over load is to look for causes of volume overload, e.g. underlying cardiac disease, sepsis, tocolytic therapy or preeclampsia. Hypovolaemic shock with cardiac, renal or other organ failure is causes of volume under load. If facilities for high-dependency care and invasive haemodynamic monitoring are unavailable, it is important to concentrate eforts on strict control of fluid balance.