gestational diabetes mellitus (GDM) is a condition where the mother has high blood sugar levels during pregnancy. GDM can increase the risk of having a macrosomic fetus, but it is not a direct cause of CPD.

Polyhydramnios is a condition where there is too much amniotic fluid around the fetus. Polyhydramnios can cause complications such as preterm labor, placental abruption, or cord prolapse, but it does not affect the size or position of the baby’s head in relation to the mother’s pelvis.

A macrosomic fetus is a fetus that is larger than average, usually weighing more than 4 kg or 8.8 lb at birth. A large fetus can cause cephalopelvic disproportion (CPD), which is a condition where the baby’s head does not fit through the mother’s pelvis during labor. CPD can lead to prolonged or obstructed labor, which can endanger both the mother and the baby.

breech presentation is a condition where the baby is positioned with its feet or buttocks first instead of its head. Breech presentation can make vaginal delivery difficult or impossible, but it does not necessarily mean that the baby’s head is too large for the mother’s pelvis.