Higher levels of estrogen and progesterone can be a prime reason why pregnant women are susceptible to sleep apnea.
The increased levels of these hormones leads to fluid retention which can affect the upper airways as you lay down to sleep.
On top of this, the hormones also relax the muscles in the body, resulting in the narrowing of the upper airways — which in tandem with excess fluid creates the conditions for OSA.
The physiological changes of weight gain — and upward shift of the diaphragm — can predispose pregnant women to have sleep apnea, including the snoring which typically occurs with OSA.
The significant rise in estrogen levels also puts women at risk since estrogen induces various changes that lead to narrowing of the airways.