Which condition may cause a sinusoidal pattern in a category 3 fetal heart strip?

A sinusoidal pattern in a category 3 fetal heart rate strip is associated with severe fetal conditions and can indicate significant fetal distress. This unique waveform is characterized by a smooth, wave-like oscillation with a regular pattern. One of the conditions that can lead to such a pattern is anemia resulting from viral diseases, particularly when these diseases impact the fetal blood supply or cause significant fetal hypoxia.

Anemia can reduce the oxygen-carrying capacity of the fetal blood. When fetal oxygen levels fall drastically, the heart may respond by producing a sinusoidal pattern, reflecting the sustained changes in fetal cardiovascular response to hypoxia. Such a heart rate pattern is a serious indication that requires immediate clinical intervention.

Other conditions mentioned may influence fetal heart patterns, but they are not primarily associated with a sinusoidal waveform. Maternal obesity can have various impacts on pregnancy, hyperstimulation of contractions typically leads to variable decelerations rather than a sinusoidal pattern, and while preeclampsia poses risks like fetal hypoxia, it does not specifically result in the classic sinusoidal pattern like anemia linked to viral diseases does. Thus, the connection between viral anemia and a sinusoidal fetal heart rate pattern is more direct and noteworthy.