Hey JM,
Oxygen therapy is the safest cluster headache abortive, even at flow rates that support hyperventilation. There are no side effects. You and your baby need oxygen to live... You can't say that about imitrex or zomig as cluster headache abortives or verapamil as a cluster headache preventative...
During a typical oxygen therapy session where you breath oxygen to abort (stop) the cluster headache and pain completely, you will breathe 100% oxygen for 3 to 20 minutes depending on the pain level.
You would need to breathe 100% oxygen continuously for 12 to 18 hours without a break breathing room air to start feeling the effects of oxygen toxicity.
How much vitamin D3 are you taking as prescribed or suggested by your OB as part of your prenatal clutch of supplements?
A consensus of several vitamin D3 experts (endocrinologists, OB/GYN, pediatricians) regarding how much to take during pregnancy and breast feeding indicates a minimum of 6000 IU/day plus the vitamin D3 cofactors... is essential... Taking more up to 10,000 IU/day is likely better.
Dr. E. Orbermer of Italy wrote the following:
“Until further experimental evidence, adequate and incontrovertible, is made available, I submit that we should play for safety. In a climate like that of England every pregnant woman should be given a supplement of vitamin D in doses of not less than 10,000 IU per day in the first 7 months, and 20,000 IU (per day) during the 8th and 9th months.”
"For the past five years I have been recommending to all personally known pregnant women to take 10,000 IU of vitaminD3 and also supplement with high dose omega 3. one young lady send me an youtube of her baby laying on daddy’s chest on her abdomen and mother called baby’s name and literally she lifted her head and looked around to see where the voice came from and mother commented that she attributes this to her supplement intake. All the children of mothers who had taken adequate amount of D3 shows remarkable alertness, agility, observation, attention and are overall very calm and always in a playful mood. I have grand parents thanking me for my recommendation."
Ashok Patel MD
Don't take my word for it... Read through the following links and see for yourself.
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

The wonderful thing about vitamin D3 is you can have its status measured with a simple lab test for 25-Hydroxyvitamin D, a.k.a. 25(OH)D. The normal reference range for this lab test is 32 to 100 ng/mL.
That makes 68 ng/mL the mid point in the "normal" reference range and a good target serum concentration of 25(OH)D to shoot for.
So ask your OB for this lab test at the first opportunity or call him to ask for this test today.
If your results come back 20-32 ng/mL, your vitamin D3 intake is insufficient. If your 25(OH)D serum concentration is less than 20 ng/mL, you're vitamin D3 deficient. Neither case is good for your baby...
See your OB and get this lab test ASAP! then work with your OB to adjust your vitamin D3 intake to achieve the ideal/target 25(OH)D serum concentration.
If you follow the chart below, you'll see that a vitamin D3 intake of 10,000 IU/day results in a serum concentration of 85 ng/mL. That's still well within the normal reference range... It is also sufficient to help prevent your cluster headaches.
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or
You'll also notice the "green zone" on this chart. That represents the range of 25(OH)D serum concentrations where 80% of the CH'ers who take vitamin D3 experience a significant reduction in the frequency, severity and duration of their cluster headaches... or go pain free...
Show this chart to your OB as well.
So there you have it... Using oxygen therapy at 15-25 liters/minute as an abortive and taking 10,000 IU/day vitamin D3 plus Omega 3 fish oil and the vitamin D3 cofactors as a cluster headache preventative provides the two safest and most effective methods of controlling your cluster headaches...
Moreover, both are safe for you and your baby... The benefits of taking sufficient vitamin D3 supplementation during pregnancy... and after... particularly if you intend to breast feed, are many...
Remember, that bump in your tummy is totally dependent on you... It's snug, warm and it's got cable... What could be better?
Take care,
V/R, Batch