Question: My wife is eight weeks pregnant, and over the last two weeks has begun to experience breathing difficulties. She has been diagnosed with bradycardia (her BPM is generally between 53 and 62 - both after excercise and rest, and even in states of extreme anxiety. Nothing seems to raise it).

Several times a day - and throughout most nights - she experiences a sensation as is someone is putting intense pressure on her chest, and cannot catch her breath. There is chest pain sometimes, and she likens the sensation to drowning. The symptoms are made worse by the attendant anxiety the sensation causes, which in turns makes breathing even harder.

Her blood pressure and oxygen saturation are both normal.

Or local doctor has offered no explanation, but has suggested that it might possibly be a physical reaction to heightened levels of progesterone in the blood (perhaps causing changes to the elasticity of the ligaments controlling movement of her ribs, and so possibly causing rubbing against the sternum - though that is purely speculation).

Our doctor seems rather XXXXXXX and has said she is not inclined to refer my wife to an obstetrician 'yet', but the symptoms are becoming unendurable. My query is - are there risks to either mother or unborn child related to bradycardia that we should be aware of? And if so, what are they? Should we be worried? Any information or insight would be gratefully received.

Dear Dr XXXXXXX

Thank you very much for your comprehensive answer.

Since we received your reply, my wife has spoken to several doctors and has been to hospital where she underwent two ECGs as well as standard blood tests (both venous and arterial - which all came back normal). After several examinations, no-one has been able to find an explanation for her bradycardia. (They have ruled out blood clots in the lung, which was one theory they put forward.

Her pulse was taken at the surgery yesterday morning (54 BPM); was a bit higher in the afternoon (sixty-something, which is the highest it has been for a couple of weeks); but was only 41 mid-morning today.

We are obviously very concerned about the possibility of bradycardia leading to harm to the developing fetus, but cannot get anyone here to give us any insight into the risks. Is it the case that there might be a lower risk of harm to the developing fetus if her blood pressure and oxygen levels are healthy (as they seem to be)? Or is a low pulse rate on its own (i.e. alongside normal blood pressure and oxygen saturation) still a cause for concern?

None of the doctors we have spoken to seem to be aware of any risks to pregnancy relating to brachycardia, and have all tried to reassure us by saying that that very fit people such as athletes get by of very low pulse rates, so we might need to worry. (My wife has always been reasonably fit, in that she would ordinarily walk the dog every day and keeps active, but is far from being an exercise enthusiast. In any case, her bradycardia is accompanied by chest pains, breathing difficulties and exhaustion, so I'm not sure I would describe her as 'fit' in this context.)

I am hoping tomorrow that we will be able to get a fetal scan done which will give us an indication of the fetal heart tone / BMP. What should this be at 8 weeks and two days? Are there any particular questions we should ask when we get to see the nurse tomorrow?

Kind regards,
XXXXXX

Thank you again for your useful reply.

My wife has had two sets of echocardiograms done now, both of which show normal heart function.

Nevertheless, my wife continues to experience these very distressing symptoms of 'drowning' and chest pain (inlcuding palpatations on the left side of her chest and left arm). These increase in occurence through the afternoon, and particularly at night.

One hypothesis we have is that this is somehow related to her body's response to progesterone. I have read that progesterone is a known stimulant of respiration and respiratory drive, and also causes a relaxation of the ligaments or muscles that control the windpipe, which from early in the first trimester leads to an increased 'ventilation' rate. I wonder whether her body is 'over-reating' to the increased progesterone levels, and the symptoms of dyspnea she is experiencing might be somehow a form of hyperventilation, caused by an 'excess' of oxygen in her blood (if such a thing is possible) - rather than a lack of oxygen, which is how she has intinctively been interpreting the sensations she experiences.
I read the following at this page:

WWW.WWWW.WW cn/uptodate/congestive%20heart%20failure/etiology/dyspnea%20during%20pregnancy.htm

"It is likely that progesterone-induced hyperventilation is at least partially responsible, perhaps due to the increase in ventilation above the level needed to XXXXXXX the rise in metabolic demand."

If that is the case, might this explain why her pulse level drops when she has these attacks? Might her heart pulse rate fall as a response to increased ventilation. i.e. having 'too much' oxygen in her blood?

Certainly, she finds that breathing into her hands (or a paper bag) provides some relief, which makes me wonder whether it is the 'rebreathing' of CO2 that helps to bring her pulse rate back up.

A number of pages talk about dyspnea during pregnancy, but none of these seem to describe the very profound and terryfying symptoms my wife experiences on a nearly daily basis. Her pulse under such circumstances has dropped from mid-60s to as low as 41. Whilst we take some comfort in your assurance that unless accompanyed by low blood pressure or low oxygen saturation, we are still very fearful of her ability to endure her pregnancy physically and mentally.

Can you tell us whether she might expect the dyspnea to increase or decrease as her pregnancy progresses (she is now nearly 9 weeks)? If her condition is related to progresterone, I am concerned that as that level rises, she might find her condition worsens. I understand that there are other physicla changes which might also make breathing more difficult later in the pregnancy: as the size and position of the uterus changes, for example.

Also - finally - referring back to my mention of the Reynauds phenomenon: Although her medical examinations this week show no current signs of low blood pressure or circulatory disorder, do you think the occasional and recurring symotoms where her fingers turn blue/black, with coldness and loss of sensation would indicate any condition that might imply a deficiency of blood oxygen? We are still very concerned that these undiagnosed/ideapathic conditions could potentially indicate something that might be threatening to the health of my wife or the fetus.

Kind regards,

XXXXXX

Progesterone is a known stimulant of respiration and respiratory drive, and its levels rise gradually rise from approximately 25 ng/mL at six weeks to 150 ng/mL at term