Repost/ Dr. RAI/ Fetal anomalies

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" A. , MD " wrote:

Date: Mon, 02 Apr 2001 16:04:38

o: thyca@...

From: " A. , MD "

Subject: Re: RAI/Fetal anomalies?

To all,

If you have had RAI for therapy, you need a follow-up scan to

evaluate the effects of therapy. The follow-up scan is generally

done in 6-12 months because of the delay between delivery of

radiation and eventual cell death in thyroid cancer. Scanning and

therapy are contraindicated in pregnancy. Therefore the number one

reason to delay pregnancy for 6-12 months, beyond any potential

issues of fetal abnormalities, is to get a follow-up scan to make

sure the therapy worked.

Jeff

At 12:58 PM 4/2/2001 -0500,

asked:

Hi All,

From what I understand from Dr Ains post(below), the main concern

for pregnancy after RAI is to have regular cycles and a normal/below

normal TSH (for fetal brain dev). He suggests to his patients

waiting 6 months after RAI.

I have read from a nuc med journal a review of pregnancies after

RAI. Of the 30 or so women, 3 got pregnant before 6 months and 2

babies had chromosomal abnormalities and the other had another

physical abnormality. They cannot prove that RAI directly caused

this but recommended women wait 12 months after RAI before becoming

pregnant. My nuc med rad also recommended waiting 12 months, my endo

said 4 WEEKS!

Is there an association between RAI and fetal anomalies? Does it

have to do with the radiation? If so, isn't that out of your system

soon after RAI? Since all of the eggs your ever going to have are

already within, how can the radiation effect be there and then go

away? Are they more susceptible to radiation during ovulation?

Does anyone know any good medical text discussing this? (I don't

want to wait 12 months.)

Dr. Ain quote:

Fetal brain development appears susceptible to maternal

hypothyroidism. This is most critical during the first 8-9 weeks of

fetal development, before the fetal thyroid becomes functional. For

that reason, one should not plan to conceive a pregnancy until the

mother's TSH is at least at or below the normal range. In addition,

therapeutic dose of I-131 may cause a temporary menstrual

irregularity which normalizes within 6 months. For these reasons, I

typically suggest that female patients who are planning a pregnancy

wait at least 6 months from their last I-131 therapy dose or 2

months from their last negative hypothyroid I-131 scan, before

discontinuing birth control.--Dr. Ain (reposted 1-01)

Thanks julie

A. , MD

Albany Medical Center

Albany, NY 12208

cooperj@...