PREGNANCY IN UNTREATED HYPOTHYROIDISM

Peter Bo,ylsn* and M. I. Drury

National Maternity Hospital, Dublin.

Summary THREE cases of success fu l p r e g n a n c y

in unt reated hypo thy ro id i sm are re- ported, The i nc i dence and t rea tmen t are d iscussed.

Introduction It is unusua l for an unt reated hypo thy -

roid woman to conce ive . We repor t 3 cases, in 2 of whom hypo thy ro id i sm was d iagnosed af ter concep t ion , wh i l s t the th i rd pa t ien t had been off t h y r o x i n e for 3 months p r io r to concept ion .

Case Reports Case 1. Mrs. B.W., aged 22 years, was 7

weeks pregnant when first seen. When aged 19, she had a thyroidectomy for hyperthyroidism. Within one, year, she had become hypothyroid and a maintenance dose of thyroxine (0.05 mg daily) was prescribed. For 3 months prior to conception she had taken no thyroxine. At her first ante-natal visit she was pale, with a haemo- globin of 9.8 gm/dl. Red cells were hypochromic and normocytic and the serum iron was 55 /zg/ dl (normal=50-150), total iron binding capacity 272 /~g/dl (normal=240-410); serum folate and vitamin B,= levels were normal. Serum thyroid stimulating hormone (TSH) was >50 p.U/ml (nor- ma1=1.7-7.0). Thyroid antibodies were not pre- sent. Thyroxine 0.3 mg daily, and ferrous sul- phate were prescribed. Two months later her haemoglobin was 12.4 gm/dl and her TSH had fallen to 15 /~U/ml. Pregnancy was uneventful until 42 weeks maturity when she became hyper- tensive. Labour was induced and a live male infant, 3020 gm, was delivered normally. The Apgar score was 9 at 1 and 5 minutes; bone age was normal; serum thyroxine was 20/~g/dl (normal =8.7-14.0), and TSH was 16/~U/ml. At 4 months of age the child was developmentally normal.

Case 2. Mrs. P.D., aged 29 years, was first seen at 23 weeks gestation in her second preg- nancy. She gave a history of cold intolerance and on examination had dry skin and hair, and a myotonic ankle jerk. Hypothyroidism was confir- med by a serum thyroxine of 1.1 /zg/dl (normal= 4.5-11.2) and a TSH of >50/~U/ml. It is probable that her hypothyroidism had existed for many

months. In spite of this, her menstrual cycle was normal and she conceived. Thyroxine was pre- scribed in gradually increasing doses up to 0.3 mg daily and continued throughout pregnancy, which was uneventful. A live born male infant (3000 gm) was delivered normally and there were no perinatal problems. Developmental assessment at 6 months was normal.

Case 3. Mrs. P. L. was diagnosed elsewhere as hypothyroid at 25 weeks in her third preg- nancy, and commenced on thyroxine; the preg- nancy ended at 36 weeks with an intra-uterine death associated with severe hypertension and proteinuria. In her present pregnancy she was seen after 6 weeks amenorrhoea, when she was taking only 0.1 mg thyroxine daily. This was in- creased to 0.2 mg daily and the pregnancy pro- gressed normally, fetal growth being monitored by ultrasound cephalometry. At 39 weeks she delivered a normal male infant weighing 3110 gm. There was transient neonatal jaundice (maxi- mum bilirubin 17 mg/dl). At one year the child was developmentally normal.

Discussion Unti l 1963 on ly 29 cases of p regnancy

and hypo thy ro i d i sm had been repor ted (Echt and Doss, 1963); 21 of t hese pat- ients had conce i ved wh i l e rece iv ing no t rea tment and in 11 of these the diag- nos is had been made af ter concep t i on ; 9 of the 21 pat ien ts wen t to term w i t h o u t t reatment . N i swande r et al (1972) , in the i r ana lys is of the co l l abo ra t i ve per i- natal s tudy of the Nat ional Ins t i tu te of Neuro log i ca l d isease and Stroke, re- v iewed 244 p regnanc ies in hypo thy ro i d women; un fo r tuna te l y they did not dis- t i ngu ish be tween t reated and unt rea ted cases. The s t i l l b i r th rate was doub led in compar i son w i th the rest of the s tudy group, a total of over 38,000 o ther preg- nancies. There is also a h igher rate of ma l fo rmat ion among ch i l d ren born to

* Present address: Research Fellow, Institute of Obstetrics and Gynaecology, University of Lon- don, Queen Charlotte's Maternity Hospital.

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PREGNANCY IN UNTREATED HYPPOTHYROIDISM 11

untreated hypothyroid women, although Echt and Doss dispute this.

Diagnosis is confirmed by a low serum thyroxine and elevated TSH. Where there is doubt about the diagnosis it is recom- mended that replacement therapy, once started, should continue until delivery, when the diagnosis can be reviewed.

The authors acknowledge the help of Dr. N. O'Brien who performed the developmental assess- ments.

References Echt, C. R. and Doss, J. F. 1963. Myxedema in

pregnancy. Obstet. Gynec. 22, 615. Niswander, K. R., Gordon, M. and Berender, H.

W. 1972. The Women and Their Pregnancies. W. B. Saunders Company. p. 246.