When does fetus use maternal thyroxine??

Question

I have had hypothyroidism for 8 years. It has been stabilized for awhile and causing no problems. I am 37 and 6 weeks pregnant. I feel great in terms of energy and health but my TSH was 3.7 so my doctor changed the dosage from 112mcg to 137mcg. We're aiming to have the level at 2.0. My question is how long before I should see changes in the TSH level? How long before it's worth testing again? Also, does the fetus only need my thyroid hormones at 11 weeks or is the baby negatively affected right now because my levels are too low? I am concerned about the research I have read about maternal hypothyroidism and fetal retardation.
When changes are made to your medication, how long in terms of weeks do you need before changing the dose?
I would appreciate any knowledge on this matter that you could share. Thank you,
Tessa

This discussion is related to Thyroid levels abnormal.

coyle · Answer

we're having these problems too. what I think would really clear things up is to explain just how the baby uses this stuff. like the tsh will be one thing then the ft3 another and the ft4 and t4 different still. For example we got pregnant while levels were being raised since we also thought it would take a year but didn't. Anyways I don't want to hijack the post but the tsh was high (coming down now) the t4 and ft4 were always good and high but the ft3 is way down at the low end of acceptable range. Where does the damage come in? is it just the ft3 that the baby uses? Our tsh levels were 6.13 at 8 weeks but then they raised the levels and 3 weeks later the lab showed 2.61 (probably went down right away) so during brain developement we just got in time. Also when you say 8-10 weeks are you referring to the time of conception or last period as there's a 2 week difference there too. Are those levels dangerous at all? I can see how it could be during that crucial time. I would love to have a complete reference to all this. anyone know of one? Thank you all and God Bless!

ovaz129 · Answer

No problem... Good luck!!!  It sounds like you are on top of your health (as more people should be, ya know?)  so I don't think that you have anything to worry about with you or your baby :)

Mabeline · Answer

Thank you so much for your comments! They are both SO helpful. You have really alleviated so much of my stress. Even though I know that other women go through the same experience and are in similar situations with the hypothyroidism, it's so nice to hear real stories of success like yours! I really wish you both the best. Good luck with everything ovaz129! I am certain you are going to have a great pregnancy and wonderful new baby! Thank you also onlyme27!
When I first read about thyroid problems and fertility, I was very sad that they said it would be harder to conceive but then we were pregnant after the FIRST time of trying!!! We had planned on it maybe taking a year but then it was right away!! So I feel like I have some positive fortune along this path! (I'm feeling lucky about this baby so far!)

onlyme27 · Answer

I went thru the same thing with my last child.  When I found out I was pregnant my levels were at 14.5!  I took 375mcg a day throughout pregnancy.  I was terrified to read about the effects of hypothyroidism on the fetus.  According to my endo, the chances of mental inabilities due to hypo are not great especially when treated early, which mine were.  I was tested every 4 weeks to make sure my levels were in check.  Now I have them checked every 3 months.  The OB and endo told me that the baby is relying on your thyroid until about the 2nd trimester when the baby's starts to kick in. As long as your are getting treatment and regular testing, you should be fine.  Oh yeah, I know tha my OB had me doing NST every visit for the entire 3rd trimester to make sure that the baby was fine.  He said that with my thryoid history I was a higher risk pregnancy.  This may not be true for everyone though.  Ask your dr about it.

ovaz129 · Answer

Hi there... I have Hashimoto's and was diagnosed 13 years ago with it.  I am currently 15 weeks pregnant.  To answer some of your questions...

1. Have your thyroid levels checked every 4 weeks
2. It takes roughly 4 weeks for your new medication to stablize your thyroid levels
3. Careful what you read on the internet... low IQ is associated with woman who did not take their medication or were not diagnosed during pregnancy and did not have adequate treatment.
4. It is critical that your levels are stable between weeks 8-10 as this is when a large part of the brain is developing.
5. Low thyroid levels will not cause retardation (that is a genetic abnormality, not something that is caused)
6. You should be seeing an endochronologist and not your OB during pregnancy for thyroid related adjustments & treatments 


You levels aren't really that off... my levels were at 2.0 up until week 12 when they shot up to 10.0.  So, 3.7 is that bad :)  I was on 112mcg as well, and during week 12 my endo put me on 137 mcg.  As you know, there is a delicate balance that needs to be maintained during pregnancy.  You don't want to give your baby too much thyroxine as that can pose just as many risks to the baby as being hypo would pose.  So, get your thyroid levels checked every 4 weeks and you should be good! :)  Good luck with your pregnancy.