Thyroid UK

Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment

TSH doesn't span the same as SPAM - otherwise I'd be putting this paper to the tune of Monty Python's famous ditty. It is repeated enough to have to play the tune ad nauseam.

When, O when, will we see proper understanding and measuring and reporting of thyroid hormones rather than TSH?

(Wouldn't it be grand if "they" insisted on TSH, FT4 and FT3 all being measured and reported in all papers - as a requirement for a) ethical approval; b) consideration for publication?)

It looks like we should be preparing to see the TSH limit go up to 4.0 - rather than 2.5.

Does anyone ever consider T3 (Free, Total or as Liothyronine/desiccated thyroid) at all?

Does anyone look at the most obvious "other" issues such as iron, B12, D, etc.? (They might be looked at individually, but in conjunction with thyroid is my point.)

BMJ. 2017 Jan 25;356:i6865. doi: 10.1136/bmj.i6865.

Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment.

Maraka S1,2, Mwangi R3, McCoy RG4,5, Yao X3,6, Sangaralingham LR3,7, Singh Ospina NM2,8, O'Keeffe DT9,10, De Ycaza AE10, Rodriguez-Gutierrez R2,11, Coddington CC 3rd12, Stan MN10, Brito JP2,10, Montori VM2,10.

Author information



To estimate the effectiveness and safety of thyroid hormone treatment among pregnant women with subclinical hypothyroidism.


Retrospective cohort study.


Large US administrative database between 1 January 2010 and 31 December 2014.


5405 pregnant women with subclinical hypothyroidism, defined as untreated thyroid stimulating hormone (TSH) concentration 2.5-10 mIU/L.


Thyroid hormone therapy.


Pregnancy loss and other pre-specified maternal and fetal pregnancy related adverse outcomes.


Among 5405 pregnant women with subclinical hypothyroidism, 843 with a mean pre-treatment TSH concentration of 4.8 (SD 1.7) mIU/L were treated with thyroid hormone and 4562 with a mean baseline TSH concentration of 3.3 (SD 0.9) mIU/L were not treated (P<0.01). Pregnancy loss was significantly less common among treated women (n=89; 10.6%) than among untreated women (n=614; 13.5%) (P<0.01). Compared with the untreated group, treated women had lower adjusted odds of pregnancy loss (odds ratio 0.62, 95% confidence interval 0.48 to 0.82) but higher odds of preterm delivery (1.60, 1.14 to 2.24), gestational diabetes (1.37, 1.05 to 1.79), and pre-eclampsia (1.61, 1.10 to 2.37); other pregnancy related adverse outcomes were similar between the two groups. The adjusted odds of pregnancy loss were lower in treated women than in untreated women if their pre-treatment TSH concentration was 4.1-10 mIU/L (odds ratio 0.45, 0.30 to 0.65) but not if it was 2.5-4.0 mIU/L (0.91, 0.65 to 1.23) (P<0.01).


Thyroid hormone treatment was associated with decreased risk of pregnancy loss among women with subclinical hypothyroidism, especially those with pre-treatment TSH concentrations of 4.1-10 mIU/L. However, the increased risk of other pregnancy related adverse outcomes calls for additional studies evaluating the safety of thyroid hormone treatment in this patient population.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to

PMID: 28122781

Full text freely available here:

10 Replies


Fertility clinics don't start treatment until TSH is <2.0. Still what do they know about how thyroid levels affect conception and pregnancy?


Sadly, again, we have seen women get to the fertility clinics without having a thyroid test, or without the result being noticed and acted on.

I say "ditto" though, to their use of TSH-only.


Obviously this paper was born in the UK by some senior Endocrinologists/Specialists who play a Pied Piper tune, so all the others follow swiftly and cannot use an independent mind and treat their patient according to their clinical symptoms. Will their findings help the mother-to-be to have a safe pregnancy or a miscarriage? Will the baby have sufficient thyroid hormones from Mum-to-be? Quote:

"However, the increased risk of other pregnancy related adverse outcomes calls for additional studies evaluating the safety of thyroid hormone treatment in this patient population."

How stupid is that, the fact that it is well-known that miscarriages can be frequent occurrences whilst hypothyroid or undiagnosed but hormone replacement should be optimum:


"calls for additional studies evaluating the safety of thyroid hormone treatment in this patient population."

I'm speechless, so will women who've had miscarriages without realising that it is common in undertreated/untreated/undiagnosed to miscarry or more worrying that it affects their baby.


Actually shaws, to quote Bruce Springsteen, born in the USA, rather than the UK!

I find it shocking that they found 5405 pregnant women with subclinical hypothyroidism. Isn't there sufficient recognition of the impact that virtually no-one gets pregnant while hypothyroid? Obviously there isn't. But it is a huge argument in favour of widespread pre-pregnancy testing and appropriate treatment. And a massive ramping up of awareness.

Much of the impact of low thyroid hormones has been reported to be in early pregnancy - so waiting until pregnancy has been confirmed is leaving it too late.

I am afraid that these "thyroid and pregnancy" papers, stories, issues often get me very close to tears.


I'm not surprised Helvella. When we read/learn we wonder how these doctors have a certificate or should I say be certified.

Babies born to severely hypo mothers will be damaged too. I don't want to even surmise how unwell these mothers must be.


Hypo Mums also have Low B12 and VITD - both of which have a profound effect on the future health of their babies ....


I totally agree that the tsh alone is useless and I'd also question the reliability of testing tsh whilst already pregnant. I happen to have had a blood test 3 weeks before I conceived - tsh was 4.87 (0.3-4.2) ft4 15.1 (12-22) but I did not see the gp, just collected results from reception (I was literally moving and intended to follow up through the new surgery). When I had my first midwife appt I mentioned the last lab results and asked to be tested. The blood test was done c. 5 weeks pregnant (2 months after the previous blood test) and the tsh was down to 1.3 (0.35-5.50), ft4 13.9 (9-21). I was told this was great and there were no more tests done during my pregnancy. I had spontaneous early labour at just under 35 weeks. My daughter's motor development was noticeably slower than her peers for the first couple of years.


I have wondered if a relative's hypothyrodism (I presume untreated at this juncture) was the reason for her severely hydrocephalus baby that died after a week.

This article cites it as a possible complication:


Back in 2011 I read an article in the Sunday Times about some research that was to take place giving obese pregnant women Metformin to ensure their babies would not become obese in the future. I wrote to the Research people mentioned and had a very patronising reply. I had asked if the women would be tested and treated for low thyroid. I cannot find the reply but still have a copy of my letter.

Back then I was not aware of how Metformin can deplete B12 - and so all those women who participated in the research ran the risk of B12D and of course unknown damage to the unborn child.

Have a feeling the above link is the research that was done - the dates seem to fit.

Was it really necessary to put women at risk - along with their babies. Low B12 in the Mother can be the cause of lower intellect in the child - sorry no links to hand ....

Betrayal springs to mind ....


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