So, here’s mine. It’s well known that caffeine is used to increase energy and ward off fatigue and sleepiness. Thus, it’s not rocket science to make the assumption that a fair number of heavy caffeine users are suffering from fatigue and sleepiness caused by sleep disorders. A potentially common sleep disorder in pregnant women is sleep-disordered breathing, a condition that causes oxidative stress and pro-inflammatory states, and previous research by the inventor of CPAP (the treatment for sleep apnea), Dr. Colin Sullivan, showed a strong link between sleep breathing problems and pre-eclampsia, a condition in pregnancy that may threaten the fetus.

Thus, a parsimonious theory is that pregnant women with sleep apnea are sufficiently tired and sleepy to reach for an extra cup of coffee, etc. So, what the research then really might be showing is that the excess caffeine drinkers actually suffer from undiagnosed sleep disorders, namely sleep-disordered breathing, which through it’s adverse effects on multiple organ systems in the body increases risk for miscarriages.

How the impact of sleep-disordered breathing (SDB) could produce this particular effect is unknown, but SDB causes a great deal of sympathetic nervous system activation by the constant awakenings triggered by disrupted breathing; and the disrupted breathing itself causes marked fluctuations or desaturations in oxygenation throughout the night. Neither of these two processes are considered healthy for the human body, so the most relevant theory would be that these processes are adversely influencing the physiology of pregnancy and the fetus.