The paper examines the case of a pregnant woman in a twin pregnancy complicated by pre-eclampsia and sleep disordered breathing. The patient was admitted to hospital with high blood pressure, proteinuria and increasing oedema. Laboratory tests revealed proteinuria and reduced total protein concentration in serum. The patient was diagnosed with mild pre-eclampsia. Due to the observed severe daytime sleepiness of the patient, loud snoring and pauses in breathing during sleep, polysomnography was performed. The test revealed a number of episodes of obstructive apnea and hypopnea. The AHI (apnea-hypopnea index) value was 82.1. A number of episodes of desaturation were observed. The lowest saturation had a value of 82%. When the patient was diagnosed with severe obstructive sleep apnea, treatment with CPAP (continuous positive airway pressure) was introduced. The use of CPAP allowed a reduction of the AHI to 1.2, and the blood pressure value normalised. The patient used CPAP between the 33rd and 35th weeks of gestation. At the 35th week of gestation, caesarean section was performed due to life-threatening symptoms of the first foetus in the CTG-recording. Two male infants were delivered in good condition. During the postpartum period, the patient discontinued the use of CPAP. Following this, an increase in AHI to 45.3 and an increase in blood pressure to a maximum of 180/100mmHg were observed. The patient was discharged from hospital in good general condition on the 7th day postpartum with recommendation for further diagnostic and therapy. The conclusion that may be drawn from the case is that sleep disorders adversely affect the health of the mother and the foetus. Also, the mood and quality of life of the pregnant woman deteriorate. It has been proven that there are many relationships between sleep and health. Sleep disorders and disorders of breathing during sleep contribute to the development of various diseases or they degrade the overall phenomena. A disease, on the other hand, additionally negatively affects the quality of sleep. Therefore, it is essential to treat not only the primary disease, but also the accompanying sleep disorders.