TKO,
Welcome to CH.com... You've come to the right place...
Please believe me, I understand your concerns... I also understand what your wife is going through with her cluster headaches and the good news is it doesn't need to be that way.
For starters, I'm not a doctor, nor am I a certified nutritionist... That said I did stay at a Holiday Inn a few years back.
Accordingly, you need to bounce all that follows off your wife's OB and neurologist. It's very important they're both singing from the same hymnal...
Have your wife see her OB for a lab test of her serum concentration of 25(OH)D. This is the serum level metabolite of vitamin D3 that's used to measure its status. The normal reference range for 25(OH)D is 30 to 100 ng/mL.
Nearly all CH'ers are vitamin D3 deficient. i.e, a serum concentration of 25(OH)D less than 30 ng/mL.
Unfortunately most physicians unfamiliar with the health benefits of vitamin D3 will say a 25(OH)D serum concentration of 31 ng/mL is "Normal."
While that may be true in order to prevent rickets... a 25(OH)D serum concentration that low will not do squat diddly for cluster headaches and it's too low for a low risk pregnancy.
We've collected 25(OH)D lab result data from hundreds of cluster headache sufferer's (CH'ers). The average 25(OH)D serum concentration before starting the anti-inflammatory regimen with 10,000 IU/day vitamin D3 was 24.3 ng/mL, (60.75 nmol/L).
80% of the CH'ers who start this regimen experience a significant reduction in the frequency, severity and duration of their cluster headaches... 75% experience several 24 hour pain free periods and 60% remain substantially pain free...
When these CH'ers had their 25(OH)D tested, the 25(OH)D serum concentration averaged 79 ng/mL.
If your wife's 25(OH)D lab test comes back indicating > 30 ng/mL or even up to 50 ng/mL, she needs to start vitamin D3 therapy asap... This is very good for her and the baby in her tummy... If she's home, call her OB about the lab test and starting the anti-inflammatory regimen asap!
Most of the vitamin D3 experts... i.e., Jedi Masters of vitamin D3 therapy, say 7,000 IU/day vitamin D3 should be taken during pregnancy. Some of the other vitamin D3 experts say pregnant ladies should take 10,000 to 15,000 IU/day... all the way through the pregnancy... and after...
In either case, both of you should talk with your wife's OB about the Anti-Inflammatory regimen. It's very safe because it's formulated with off-the-shelf nutrients, vitamins and minerals that are all very healthy for women during pregnancy.
The following link will provide you and your wife with your reading assignment for the evening.
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As you'll see, opinions among the experts differ slightly on the dose to take... That said, all are convinced your wife needs vitamin D3 during pregnancy... and after... It makes for better breast milk for the baby...
Most vitamin D3 experts say 60 ng/mL is a good target 25(OH)D serum concentration to shoot for during pregnancy...
Please understand... that's for normal, otherwise healthy women... not a pregnant lady with cluster headaches...
As a CH'er... your wife falls into another category... She will need to shoot for a 25(OH)D serum concentration range of 60 to 110 ng/mL, or an average of 85 ng/mL.
The important thing to understand about proper vitamin D3 therapy is we need to take more than just the vitamin D3... We also need the vitamin D3 cofactors... These are the essential supplements that aid in vitamin D3 metabolism... They include: calcium, magnesium, zinc, boron, vitamin A (retinol) and vitamin K2 (MK-4 & MK-7).
You'll find the complete anti-inflammatory regimen "How To" guide with the list of supplements, suggested doses, vitamin D3 dosing strategy, drug interactions and contraindications at the following link:
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You can also find a condensed version at VitaminDWiki at the following link:
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The bottom line is your wife needs to be taking a minimum of 7,000 IU/day vitamin D3... 10,000 to 15,000 IU/day is likely even better for her and the baby.
After your child's birth. both mother and baby need vitamin D3 supplementation, particularly if breast feeding.
Again, talk with your wife's OB... if he or she comes down with anal leakage over the suggested doses of vitamin D3 or the target 25(OH)D serum concentration your wife needs to maintain in order to stay cluster headache pain free... take along some of the material from the VitaminDWiki web site WRT vitamin D3 during pregnancy...
If my wife was pregnant, I'd be saying the same thing... except that would be a medical rarity as she's kicked the heck out of 76 and turns 77 in December... Go figure... I'd also tell her to use oxygen therapy as a custer headache abortive...
There are a number of articles that say taking sumatriptan succinate, (imitrex) as a cluster headache abortive, and verapamil as a cluster headache preventative are OK during pregnancy... I disagree... and I would argue my wife and her neurologist out of her taking either of them...
My wife also takes the same anti-inflammatory regimen as I do as a chronic CH'er... except she's been taking 15,000 IU/day since she started this regimen in December of 2010. She looks great, feels great, and has more energy than I've seen in 20 years.
She was also a chronic migraineur with migraines hitting once a month for 3 to 5 days in duration like clockwork... She hasn't had a single migraine headache since she started this regimen...
One last note... You need to be on this same regimen as well... The health benefits are too numerous to count... The only note of caution is when both you and your wife are on this regimen... fertility can go up significantly...

Please feel free to PM me with questions... If you're anything like I was when my wife got pregnant for the first time... you've got more questions than Carter's Little Liver Pills...
Take care and please do keep us posted on your wife's progress...
V/R, Batch