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PubMed · 809559

Thyroxine in human amniotic fluid.

J Sack·D A Fisher·C J Hobel·R Lam
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Abstract

Total and free T3 and T4 concentrations were measured in human amniotic fluid and in fetal and maternal blood. Before 20 weeks, the mean AF-T4 level was 0.24 mug/dl; there is a progressive increase in concentration with gestational age. At term, the mean AF total T4 level was much less (0.64 mug/dl) than in fetal or maternal serum (9.3 and 11.3 mug/dl, respectively). Most of the T4 (99.4%) in AF is protein bound, presumably to TBG as in serum, but the mean FT4 concentration in AF at term (4.13 ng/dl) was significantly greater than the levels in fetal or maternal serum (2.67 or 2.56 ng/dl, respectively). The mean TBG level in AF at term was 0.26 mg/dl. T3 was not measurable in AF (less than 15 ng/dl). There were no significant correlations between the total or free T4 concentrations in maternal or fetal sera and in amniotic fluid. Thus AF thyroid hormone concentrations in the euthyroid fetus do not reliably reflect fetal serum T4 or T3 concentrations.

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AmniocentesisAmniotic FluidFemaleFetal BloodGestational AgeHumansInfant, NewbornPregnancyRadioimmunoassayThyroxineThyroxine-Binding ProteinsJournal ArticleResearch Support, U.S. Gov't, P.H.S.

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J Sack, D A Fisher, C J Hobel, R Lam. 1975. Thyroxine in human amniotic fluid.. https://doi.org/10.1016/s0022-3476(75)80636-6

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Antenatal maternal serum screening for Down's syndrome: results of a demonstration project.

OBJECTIVES: To assess the implementation of antenatal screening for Down's syndrome in practice, using individual risk estimates based on maternal age and the three serum markers: alpha fetoprotein, unconjugated oestriol, and human chorionic gonadotrophin. DESIGN: Demonstration project of Down's syndrome screening; women with a risk estimate at term of 1 in 250 or greater were classified as "screen positive" and offered diagnostic amniocentesis. SETTING: Hospital and community antenatal clinics in four health districts in London. SUBJECTS: 12,603 women of all ages with singleton pregnancies seen between February 1989 and the end of May 1991, with follow up of the outcome of pregnancy completed to the end of 1991. MAIN OUTCOME MEASURES: Uptake of screening, detection rate for Down's syndrome, false positive rate, odds of being affected given a positive result, and uptake of amniocentesis in women with positive screening results, together with the costs of the screening programme. RESULTS: The uptake of screening was 74%. The detection rate was 48% (12/25), and the false positive rate was 4.1%, consistent with results expected from previous work based on observational studies. There was a loss of detection due to the selective use of ultrasound scans among women with positive screening results. One affected pregnancy occurred among 205 reclassified as negative; this illustrated the danger of false negatives occurring in this group and lends weight to the view that if an ultrasound estimate of gestational age is used it should be carried out routinely on all women rather than selectively among those with positive results. The estimated cost of avoiding the birth of a baby with Down's syndrome was about 38,000 pounds, substantially less than the lifetime costs of care. CONCLUSION: Antenatal maternal serum screening for Down's syndrome is effective in practice and can be readily integrated into routine antenatal care. It is cost effective and performs better than selection for amniocentesis on the basis of maternal age alone.

Amniocentesis↗