Amniotic fluid testosterone and follicle-stimulating hormone in the determination of fetal sex

A window for the study of prenatal sex hormone influences on postnatal development

In humans, the influence of prenatal sex hormones on the fetal brain and subsequent postnatal development has had limited study because of the apparent inaccessibility of hormone levels in normal fetuses. We propose that amniotic fluid obtained via midtrimester amniocentesis can be assayed for fetal hormone levels during the period thought to be important for sexual differentiation of the brain. Amniotic fluid samples from midgestation (N = 70) were assayed for levels of testosterone and follicle-stimulating hormone, and significant sex differences were observed (ps less than .001), with some degree of overlap between the sexes. The possibility of applying hormone levels obtained from amniotic fluid to the study of postnatal development is discussed.

Fetal control of maternal prolactin production and bioactivity in utero

Amniotic fluid prolactin is a product of maternal decidualized endometrium that is derived by translocation of the hormone across the reflected fetal membranes. Amniotic fluids from 26 second-trimester (14 to 23 weeks) and 75 third-trimester (29 to 40 weeks) normal singleton pregnancies were evaluated for prolactin content by radioimmunoassay and bioassay with the Nb2 rat lymphoma cell line. The relative bioactivity was calculated as the ratio of bioassay to radioimmunoassay for each fluid. Data segregated by gestational age and fetal genetic sex identified a highly significant difference (p = 0.0004) in amniotic fluid prolactin radioimmunoassay concentrations (mean +/- SEM) that surround male (682 +/- 49, n = 42) versus female (440 +/- 39, n = 33) fetuses of third-trimester age. Paired bioassay values were significantly lower (p = 0.002) than radioimmunoassay values among males (626 +/- 52) but equivalent (p = 0.1066) among females (464 +/- 44). The bioassay/radioimmunoassay ratios of third-trimester fetal female-associated amniotic fluid prolactin were significantly higher (p = 0.0004) than those of third-trimester males and second-trimester males and females. The results suggest a fetal gender-related factor is associated with both the production and the biologic activity of the maternally derived hormone. Thus the fetus appears to have some control over the dynamics of uterine prolactin production.

Amniotic fluid testosterone and testosterone glucuronide levels in the determination of foetal sex

Unconjugated testosterone levels were assayed in 351 amniotic fluid samples obtained at 15-19 weeks gestation. The median values for unconjugated testosterone in the 166 female foetuses and 185 male foetuses were 137 and 712 pmol/l respectively. Sixteen amniotic fluid samples from male foetuses had unconjugated testosterone levels lower than the highest female unconjugated testosterone value (361 pmol/l). Testosterone glucuronide was measured in amniotic fluid from 48 female and 55 male foetuses. There was a significant sex difference in the median values of testosterone glucuronide between female (median 160 pmol/l, range 64-465 pmol/l) and male (median 817 pmol/l, range 68-3707 pmol/l) amniotic fluid specimens (P less than 0.001). Of the sixteen male foetuses with amniotic fluid unconjugated testosterone levels in the female range, 12 had amniotic fluid testosterone glucuronide levels within the male testosterone glucuronide range of values. Hence used in conjunction with unconjugated testosterone, testosterone glucuronide increased the predictive accuracy of foetal sexing from 95.4 to 98.9%. Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no Testosterone sulphate was measured in 24 female and 25 male amniotic fluid samples. There was no significant difference between female (median 2591 pmol/l) and male (median 2964 pmol/l) testosterone sulphate levels.

Testosterone assays: guidelines for the provision of a clinical biochemistry service

Approximately one year after the devolution of testosterone assays from the SAS, the Analytical Methods Working Party of the Association of Clinical Biochemists set up a working party to investigate the performance of the assays, to survey the available methodology and to give guidance on the factors that influence the assay. This document represents a summary of the deliberations of the group and forms one of a series of similar reports.

Prenatal sex diagnosis: testosterone and FSH levels in mid-trimester amniotic fluids

We studied the validity of mid-trimester amniotic fluid testosterone and FSH in the diagnosis of fetal sex in abnormal fetuses and in twins. It was found that the testosterone/FSH ratio, but not the level of the individual hormones, was an excellent criterion for fetal sex diagnosis. In a control group of 32 female and 34 male fetuses, the testosterone/FSH ratio was diagnostic. In two cases the values were indeterminate and fetal sex could not be predicted, but there were no false diagnoses. The abnormalities of the fetuses were diagnosed by karyotype analyses or raised levels of alpha-fetoprotein. It was found that neither autosomal trisomies nor X-chromosome aneuploidy or neural tube defect interfered with the diagnostic value of the hormonal approach. The twin study included 14 pairs, three of whom were discordant for sex. In all twins the fetal sex diagnosis was appropriate. In co-twins of the same sex the hormone levels were very close to each other.

Fetal sex dependent hormone levels in early pregnant women with elevated maternal serum alpha-fetoprotein

Maternal serum and amniotic hormone levels have been investigated in two groups of women in pregnancy weeks 18-21. One group (B) was composed of women with high alpha-fetoprotein levels in serum without fetal abnormality, and a matched control group (A) with normal alpha-fetoprotein levels in serum. Amongst group B women were four pregnancy complications: two spontaneous abortions, one premature delivery, and one cesarean section due to fetal asphyxia. Group B women were significantly different from group A women. Thus, higher maternal serum levels of total estriol (P = 0.030), testosterone (P = 0.016), and alpha-fetoprotein (P = 0.018) were noted in the presence of male fetuses; and higher hPL (P = 0.004), FSH (P = 0.037), and alpha-fetoprotein (P = 0.002) concentrations in women carrying female fetuses, who were accompanied by lower total estriol concentrations (P = 0.045). Differences between groups B and A in terms of amniotic fluid analyses were only related to female fetal sex. Thus, group B showed higher hPL (P = 0.028), testosterone (P = 0.020), and FSH (P = 0.006) levels, and lower alpha-fetoprotein (P = 0.013) concentrations. It is concluded that elevated maternal serum levels of alpha-fetoprotein are accompanied in female fetuses by an endocrine milieu different from that of matched controls. This difference may put the conceptus at a disadvantage, but the majority of the girls were born on time without signs of small-for-date.

Amniotic fluid testosterone and fetal sex determination (discussion of the endocrine function of the fetal testis)

Amniotic fluid testosterone levels were determined by the radioimmunoassay technique in 101 samples obtained by amniocentesis between 16 and 18 weeks of gestation from women with increased risk of chromosomal abnormalities. Fetal sex was determined by cell culture and chromosomal analysis of fetal amniotic cells and was confirmed at birth. In pregnancies with male fetuses (50 samples), the mean amniotic fluid testosterone level of 216 pg/ml (+/- 75) was significantly higher (p less than 0.001) than the mean value of 93 pg/ml (+/- 28) found in pregnancies with female fetuses (51 samples). The range for pregnancies with male fetuses was 130 to 500 pg/ml and for those with female fetuses 10 to 140 pg/ml, showing an area of overlap from 130 to 140 pg/ml.

Changes in maternal serum total and free androgen levels in early pregnancy: lack of correlation with fetal sex

The fetal testis actively produces androgens during early gestation. To determine whether this fetal production of androgens might be reflected by levels of androgens in maternal serum, which might then be a useful test for antenatal fetal sex determination, we measured serum testosterone (total and free) and serum dihydrotestosterone in 83 pregnant women whose fetuses ranged from 4 to 20 weeks in age. For no maternal serum androgen measured was there a significant difference between women carrying a male fetus and those carrying a female fetus, even when this comparison was limited to various 4-week subintervals or fetal age. Total serum testosterone correlated directly with fetal age (r = 0.341, p less than 0.005), but serum dihydrotestosterone did not (r = 0.146, p = NS). Inverse correlations with fetal age were observed for percentage free testosterone (r = -0.531, p less than 0.001) as well as absolute serum free testosterone (r = -0.349, p less than 0.005). We conclude that maternal serum androgen levels are not useful for antenatal fetal sex determination in early pregnancy. The reason for the progressive fall in serum free testosterone, and presumably androgen production, during early gestation remains obscure.

Maternal serum human chorionic gonadotropin concentrations and fetal sex prediction

The feasibility of using maternal serum human chorionic gonadotropin (hCG) concentrations for prenatal sex prediction was examined. hCG was mesured in 822 serum samples from 560 women with uncomplicated pregnancies. Significantly higher hCG concentrations were found in the serum of women bearing female fetuses than in the serum of women bearing male fetuses during the third trimester, especially during the 10th lunar month. The data were utilized to construct probability graphs for fetal sex prediction based upon a single maternal serum hCG determination during the third trimester and during the 10th lunar month. However, the utility of these graphs is limited by the small proportion of pregnant women with serum hCG concentrations that were high or low enough to allow a prediction with high probability.

Prenatal diagnosis of fetal sex by amniotic fluid testosterone and FSH, and their potential use in detecting sex linked disorders

Amniotic fluid testosterone was assayed by radioimmunoassay in 971 samples at 16-18 weeks gestation. FSH assay was performed in 353 of these samples. Correct prediction of fetal sex (46%) was made in all samples with a testosterone level above 338 ng/L for all males, and below 162 ng/L for females. For 45% of samples with FSH levels below 7.6 IU/L for males and 10.9 IU/L for females the fetal sex was predicted correctly. By using a testosterone/FSH ratio, the diagnostic accuracy was 80%. The anmiotic fluid of ten Duchenne Muscular Dystrophy carrier mothers were studied and only the sex of one case could not be predicted. The amniotic fluid testosterone and FSH assays could be used as a rapid biochemical screening method for predicting fetal sex in X-linked disorders before birth.

The prenatal determination of fetal sex: amniotic fluid testosterone as a preliminary screening test

Amniotic fluid testosterone levels were measured by radioimmunoassay without chromatography on 101 specimens obtained at amniocenteses between 15 and 19 wk gestation. For the male fetus, the amniotic fluid testosterone level of 553 +/- 23 pmol/l (mean +/- SE) was significantly higher (P less than 0.0005) than the concentration found for the female fetus (206 +/- 9 pmol/l). There was an overlap of the ranges 74-1120 pmol/l for the male and 122-399 pmol/l for the female fetuses. Amniotic fluid testosterone levels above 400 pmol/l were observed in 84% of the male and in none of the female fetuses. The method allowed determination of testosterone levels within 8 h. It is concluded that amniotic fluid testosterone measured by radioimmunoassay without chromatography is a rapid and effective preliminary screening test for the prenatal diagnosis of fetal sex.

Amniotic fluid testosterone and follicle-stimulating hormone assay in the prenatal determination of fetal sex

Amniotic fluid testosterone was assayed by radioimmunoassay in 812 samples taken at 16 weeks' gestation at the time of genetic amniocentesis. In each of 361 samples (45% of total), correct assignment of fetal sex was made where the testosterone level was above 33.8 ng/ml for male fetuses and below 16.2 ng/ml for female fetuses. In each of 159 of 353 (45%) samples assayed for follicle-stimulating hormone (FSH), levels were below 7.6 mlU/ml for male fetuses and above 10.9 mlU/ml for female fetuses. By combining the two assays in the testosterone/FSH ratio, correct assignment of sex was made in each of 282 samples (80%). The percentage of samples in which correct assignment was achieved was greater for female fetuses (ratio less than 2.2 in 161/187 [86%]) than for male fetuses (ratio greater than 3.4 in 121/166 [72%]). The testosterone/FSH ratio holds promise as a rapid biochemical screening tool in the prenatal diagnosis of fetal sex in X-linked disorders.

[Prenatal sex determination by radioimmunoassay of testosterone with and without chromatography of the amniotic fluid (author's transl)]

Amniotic fluid testosterone measured by radioimmunoassay (RIA) without chromatography (immunoreactive testosterone) seems not to be a definitive test for prenatal sex determination in all cases. In this study testosterone (T) levels measured by RIA with chromatography of the amniotic fluid samples were compared with immunoreactive testosterone (iT) values, to determine the predictive accuracy of the two methods. In 111 amniotic fluid samples between 15 and 19 weeks of gestation iT and T were measured parallelly. There are significant differences between iT- and T-means of both sexes (p less than 0.001). 95%-condifence limits of iT-values of the male and female fetuses are largely overlapping. In contrast, the overlap of 95%-confidence limits of the T-values is only minor. The measurement of testosterone with chromatography of the amniotic fluid samples shows for prenatal sex determination in over 90% accuracy. This result is due to the elimination of sex-specific differences in crossreacting steroids within the amniotic fluid of both sexes.