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Early amniocentesis: alphafetoprotein levels in amniotic fluid, extraembryonic coelomic fluid and maternal serum between 8 and 13 weeks
Author(s) -
WATHEN NEVILLE C.,
CASS PETER L.,
CAMPBELL D. JAMES,
KITAU MURIEL J.,
CHARD TIM
Publication year - 1991
Publication title -
bjog: an international journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.157
H-Index - 164
eISSN - 1471-0528
pISSN - 1470-0328
DOI - 10.1111/j.1471-0528.1991.tb13507.x
Subject(s) - amniotic fluid , amniocentesis , coelom , gestation , medicine , gestational age , obstetrics , fetus , andrology , pregnancy , prenatal diagnosis , anatomy , biology , genetics
Objective— The aim was to establish a normal range of alphafetoprotein (AFP) concentrations in amniotic fluid from 8 to 12 weeks gestation, and to determine any difference between AFP levels in amniotic fluid and extraembryonic coelomic fluid. Design and subjects— 150 women had a transvaginal ultrasound guided amniocentesis before termination of an apparently normal first trimester pregnancy. Separately identified samples of amniotic fluid and extraembryonic coelomic fluid were obtained and assayed by radioimmunoassay for AFP. Results— In amniotic fluid, very high levels of AFP were present at 8 weeks, levels falling rapidly up to 10 weeks after which there was a slight rise. Thus over the period 8 to 10 weeks, there was a significant inverse correlation between amniotic fluid AFP and gestational age ( r = 0.67 ; P <0.001 ). In extraembryonic coelomic fluid, by contrast there was no trend in AFP relative to gestational age. Conclusions— The rapidly changing levels of AFP from 8 to 10 weeks as well as the small volume of the amniotic cavity makes the use of amniocentesis impracticable before 11 weeks gestation. The lack of any relation between AFP levels in amniotic fluid and extraembryonic coelomic fluid emphasises the importance of identifying the site of amniocentesis in the first trimester.