Maternal Serum Steroid Levels Are Unrelated to Fetal Sex: A Study in Twin Pregnancies

Steroid Metabolome Analysis in Dichorionic Diamniotic Twin Pregnancy

Steroid hormones have diverse roles in pregnancy; some help stabilise pregnancy and influence the stability of pregnancy and the onset of labour. Changes and disorders in steroidogenesis may be involved in several pregnancy pathologies. To date, only a few studies have performed a very limited steroid analysis in multiple pregnancies. Our teams investigated multiple pregnancies regarding the biosynthesis, transport, and effects of steroids. We recruited two groups of patients: pregnant women with multiple pregnancies as the study group, and a control singleton pregnancies group. Blood samples were drawn from the participants and analysed. Information about the mother, foetus, delivery, and newborn was extracted from medical records. The data were then analysed. The gestational age of twin pregnancies during delivery ranged from 35 + 3 to 39 + 3 weeks, while it was 38 + 1 to 41 + 1 weeks for the controls. Our findings provide answers to questions regarding the steroidome in multiple pregnancies. Results demonstrate differences in the steroidome between singleton and twin pregnancies. These were based on the presence of two placentae and two foetal adrenal glands, both with separate enzymatic activity. Since every newborn was delivered by caesarean section, analysis was not negatively influenced by changes in the steroid metabolome associated with the spontaneous onset of labour.

Developmental programming: Impact of preconceptional and gestational exposure to a real-life environmental chemical mixture on maternal steroid, cytokine and oxidative stress milieus in sheep

BACKGROUND

Gestational exposure to environmental chemicals (ECs) is associated with adverse, sex-specific offspring health effects of global concern. As the maternal steroid, cytokine and oxidative stress milieus can have critical effects on pregnancy outcomes and the programming of diseases in offspring, it is important to study the impact of real-life EC exposure, i.e., chronic low levels of mixtures of ECs on these milieus. Sheep exposed to biosolids, derived from human waste, is an impactful model representing the ECs humans are exposed to in real-life. Offspring of sheep grazed on biosolids-treated pasture are characterized by reproductive and metabolic disruptions.

OBJECTIVE

To determine if biosolids exposure disrupts the maternal steroid, cytokine and oxidative stress milieus, in a fetal sex-specific manner.

METHODS

Ewes were maintained before mating and through gestation on pastures fertilized with biosolids (BTP), or inorganic fertilizer (Control). From maternal plasma collected mid-gestation, 19 steroids, 14 cytokines, 6 oxidative stress markers were quantified. Unpaired t-test and ANOVA were used to test for differences between control and BTP groups (n = 15/group) and between groups based on fetal sex, respectively. Correlation between the different markers was assessed by Spearman correlation.

RESULTS

Concentrations of the mineralocorticoids - deoxycorticosterone, corticosterone, the glucocorticoids - deoxycortisol, cortisol, cortisone, the sex steroids - androstenedione, dehydroepiandrosterone, 16-OH-progesterone and reactive oxygen metabolites were higher in the BTP ewes compared to Controls, while the proinflammatory cytokines IL-1β and IL-17A and anti-inflammatory IL-36RA were decreased in the BTP group. BTP ewes with a female fetus had lower levels of IP-10.

DISCUSSION

These findings suggest that pre-conceptional and gestational exposure to ECs in biosolids increases steroids, reactive oxygen metabolites and disrupts cytokines in maternal circulation, likely contributors to the aberrant phenotypic outcomes seen in offspring of BTP sheep - a translationally relevant precocial model.

Association between prenatal androgens and cord blood androgens, a path analysis

To determine association paths between prenatal androgens and cord blood androgens. The concentrations of T, FT, DHT, DHEA and SHBG in prenatal venous blood and cord blood were measured in 342 pregnant women and their neonates. The association paths between these hormones in prenatal and cord blood were revealed using Pearson correlation, multiple linear regression and path analysis. CB-T, CB-FT and CB-DHT in male neonates were higher than those in female neonates. In male and female neonates, P-FT was lower than CB-FT; however, P-DHT and P-SHBG were higher than CB-DHT and CB-SHBG, respectively. P-DHEA was lower than CB-DHEA in female newborns. In male neonates, there were association paths of P-T → CB-T → CB-FT → CB-DHT, P-T → CB-FT → CB-DHT, P-T → P-FT → CB-FT → CB-DHT, P-T → P-DHT, CB-DHEA → CB-DHT, CB-DHEA → P-DHT, and CB-DHEA → P-DHEA. In female neonates, there were association paths of P-T → CB-T → CB-FT → CB-DHT, P-T → P-FT → CB-FT → CB-DHT, P-T → P-FT → P-DHT, P-T → P-DHT, P-DHEA → P-DHT, CB-DHEA → P-DHEA, and CB-DHEA → CB-FT. There were differences in the T, FT and DHT concentrations in cord blood between male and female neonates and in the FT, DHT, DHEA, and SHBG concentrations between prenatal and cord blood. P-T and P-FT concentrations were positively associated with CB-T and CB-FT concentrations, while CB-DHEA concentration was positively associated with P-DHEA concentration.

Primary tooth size asymmetry in twins and singletons

OBJECTIVES

To explore asymmetry values of antimeric deciduous tooth crown dimensions in three types of twins: monozygotic (MZ), dizygotic same-sex (DZ) and opposite-sex (OS) vs. single-born controls.

SETTING AND SAMPLE POPULATION

Mesiodistal and labio-lingual crown dimensions of second deciduous molars and mesiodistal canine and first molar crown dimensions of 2159 children at 6-12 years of age were evaluated, originating from the US cross-sectional Collaborative Perinatal Study from the 1970s, including altogether MZ (n = 28), DZ same-sex (n = 33) and OS (n = 39) pairs. Single born (n = 1959) were used as controls.

MATERIAL AND METHODS

Dental casts were measured for comparison of variance relationships calculated from antimeric teeth, exhibiting fluctuating (FA), and directional (DA) asymmetry using anova.

RESULTS

Significant differences appeared in MZ and OS girls in DA of deciduous canines, which gain size in the first and second trimester, and deciduous second molars, which finally stop crown growth during the early post-natal period. Significantly, increased FA values appeared for lower deciduous canines and second molars, indicating greatest environmental stress in OS girls, MZ girls and DZ boys. Twin girls had more fluctuating and directional crown asymmetry than twin boys, but in some dimensions, the twins were more symmetric than controls.

CONCLUSIONS

Transmembrane hormonal influence between opposite-sex twins, and late gestational stress factors, caused by placental malfunction and/or monochorionicity, may be involved in asymmetric growth of antimers, during critical periods of crown size gain.

Characterization of estrogens, testosterone, and cortisol in normal bottlenose dolphin (Tursiops truncatus) pregnancy

The goal of this study was to describe profiles of serum estrogens, testosterone and cortisol during normal pregnancy in bottlenose dolphins. Predominant estrogens in all categories of dolphin sera pools during estrus and pregnancy (EARLY: Days 0-120; MID: Days 121-240; LATE: Days 241 to parturition; Day 0=day of conception) were estrone/estrone conjugates (E1-C) and estriol (E3). Serum samples collected throughout 101 normal pregnancies were analyzed for E1-C, E3, testosterone (T) and cortisol (CORT). E1-C was higher (P<0.05) during LATE compared to EARLY and MID, and higher (P<0.05) in nulliparous than multiparous females. E1-C concentrations were also inversely associated with maternal age (P=0.05). E3 was higher (P<0.05) in EARLY than MID and LATE, and higher overall for nulliparous than multiparous females, but concentrations were similar among gestational stages when parity was excluded from analyses. Analysis by indexed month post-conception (IMPC) demonstrated that E1-C increased from IMPC 9 and peaked at IMPC 11. E3 was significantly elevated during IMPC 1, decreased until IMPC 6 and peaked at IMPC 11. T increased (P<0.05) at IMPC 3 and continued to increase throughout gestation (P<0.05). CORT was higher (P<0.05) during LATE compared to EARLY and MID (P<0.05), peaked during IMPC 12, and was not affected by parity. Hormone profiles were not influenced by fetal sex.

Risk of Sex-Specific Cancers in Opposite-Sex and Same-Sex Twins in Denmark and Sweden

BACKGROUND

Increasing evidence shows that some cancers originate in utero. It is hypothesized that elevated exposure to some steroid hormones might increase cancer risk and that hormone transfer between twin fetuses could result in different prenatal exposure to testosterone.

METHODS

This large-scale prospective twin study compared opposite-sex (OS) and same-sex (SS) twins to test the impact of intrauterine exposures on cancer risk. On the basis of the Danish and Swedish twin and cancer registries, we calculated incidence rate ratios for OS and SS twins, whereas standardized incidence ratios (SIR) with 95% confidence intervals (CI) were calculated for OS/SS twins compared with the general population.

RESULTS

A total of 18,001 cancers were identified during 1943-2009. No significant differences were observed between OS and SS twins, neither for the sex-specific cancers nor for cancer at all sites. All-cause cancer was slightly reduced for OS and SS twins compared with the general population, significant for OS males (SIR, 0.95; 95% CI, 0.92-0.98) and for SS males and females (SIR, 0.97; 95% CI, 0.94-0.99).

CONCLUSIONS

Our data suggest that having a male co-twin-which may entail higher exposure to prenatal testosterone-does not increase the risk of sex-specific cancers in OS females. Furthermore, the study supports that twinning per se is not a risk factor of cancer.

IMPACT

Findings are reassuring, as they fail to provide evidence for the hypothesis that endocrine or other difference in the in utero milieu affects the risk of sex-specific cancers.

Sex-specific associations of maternal prenatal testosterone levels with birth weight and weight gain in infancy

Associations between maternal salivary testosterone at 36 weeks' gestation with birth weight and infant weight gain through 6 months of age were examined in a group of 49 healthy, pregnant women and their offspring. The diurnal decline of maternal testosterone was conserved in late pregnancy, and levels showed significant day-to-day stability. Elevated maternal morning testosterone level was associated with lower birth weight Z-scores adjusted for gestational age and sex, and greater infant weight gain between birth and 6 months. Although maternal testosterone levels did not differ by fetal sex, relations were sex-specific such that maternal testosterone had a significant impact on weight for male infants; among female infants associations were nonsignificant. Results highlight the opposing influence of maternal androgens during pregnancy on decreased growth in utero and accelerated postnatal weight gain.

Measurement of androgen and estrogen concentrations in cord blood: accuracy, biological interpretation, and applications to understanding human behavioral development

Accurately measuring hormone exposure during prenatal life presents a methodological challenge and there is currently no "gold standard" approach. Ideally, circulating fetal hormone levels would be measured at repeated time points during pregnancy. However, it is not currently possible to obtain fetal blood samples without significant risk to the fetus, and therefore surrogate markers of fetal hormone levels must be utilized. Umbilical cord blood can be readily obtained at birth and largely reflects fetal circulation in late gestation. This review examines the accuracy and biological interpretation of the measurement of androgens and estrogens in cord blood. The use of cord blood hormones to understand and investigate human development is then discussed.

Hormones and endocrine-disrupting chemicals: low-dose effects and nonmonotonic dose responses

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of "the dose makes the poison," because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from the cell culture, animal, and epidemiology literature. We illustrate that nonmonotonic responses and low-dose effects are remarkably common in studies of natural hormones and EDCs. Whether low doses of EDCs influence certain human disorders is no longer conjecture, because epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities. We conclude that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses. Thus, fundamental changes in chemical testing and safety determination are needed to protect human health.

The relevance of the epidemiology of human sex ratios at birth to some medical problems

The human sex ratio (proportion male at birth) shows considerable variation which is central to reproductive epidemiology. For example, it has reportedly shown significant secular trends and wartime variation, and it has shown replicated variation with parental exposure to several deleterious chemicals. However, scientific progress in identifying the causes of these forms of variation has been very slow and, as described here, this has elicited some scepticism. Benefits may be expected from identifying these causes. Two (non-competing) hypotheses have emerged, the first relating to the hormonal regulation of sex ratio at conception, and the second to the sex-selective effects of stressors during pregnancy. It is shown here that if the first of these hypotheses was substantially correct, it would illuminate a number of scientific and medical problems, for example, the causes of autism and of selected sex-related congenital malformations and obstetric pathologies.

A potential explanation of some established major risk factors for autism

Baron-Cohen hypothesized that a cause of autism in infants is exposure to high concentrations of intrauterine testosterone concentrations. Some of the subsequent research on this hypothesis has focused on the possibility that the source of this testosterone is the fetus; however, this review shows that if the source is taken to be the mother, then many of the established risk factors for autism could be explained. If that were correct, it would follow that high maternally derived intrauterine androgen concentrations may be a major environmental cause of autism.

Decreased prevalence of left-handedness among females with male co-twins: evidence suggesting prenatal testosterone transfer in humans?

Studies of singletons suggest that right-handed individuals may have higher levels of testosterone than do left-handed individuals. Prenatal testosterone levels are hypothesised to be especially related to handedness formation. In humans, female members from opposite-sex twin pairs may experience elevated level of prenatal exposure to testosterone in their intrauterine environment shared with a male. We tested for differences in rates of left-handedness/right-handedness in female twins from same-sex and opposite-sex twin pairs. Our sample consisted of 4736 subjects, about 70% of all Finnish twins born in 1983-1987, with information on measured pregnancy and birth related factors. Circulating testosterone and estradiol levels at age 14 were available on 771 and 744 of these twins, respectively. We found significantly (p=.006) lower prevalence of left-handedness in females from opposite-sex pairs (5.3%) compared to females from same-sex pairs (8.6%). The circulating levels of neither testosterone nor estradiol related to handedness in either females or males. Nor were there differences in circulating testosterone or estradiol levels between females from opposite-sex and same-sex twin pairs. Birth and pregnancy related factors for which we had information were unrelated to handedness. Our results are difficult to fully explain by postnatal factors, but they offer support to theory that relates testosterone to formation of handedness, and in a population-based sample, are suggestive of effects of prenatal testosterone transfer.

Testosterone treatment of pregnant rabbits affects sexual development of their daughters

The intrauterine position (IUP) may affect the sexual development of a female fetus in litter-bearing mammals. Females gestating between two males (2M) develop into masculinized adults compared to females without contiguous males (0M). Fetuses are known to secrete different types and amounts of steroid hormones during the prenatal period, and diffusing steroids may affect sexual differentiation of their neighbors, too. Exposure of elevated testosterone (T) levels generally results in masculinized anatomy and behavior in females of several rodent species. Our recent study showed that IUP-dependent masculinization is also present in the domestic rabbit, which shows large variation in sex related traits as adults. The aim of the present study was to test if the IUP effect in rabbits can be induced by exogenous testosterone treatment. By administering different doses of testosterone propionate (TP) to pregnant rabbits, and following anatomical and behavioral development of their female offspring, we obtained dose-dependent increase both in the anogenital distance (AGD) and chin-marking behavior of prenatal T exposed females. The effects of treatment corresponded to the variation due to intrauterine position in our previous study, namely, exposure to T of known external origin resulted in similar tendencies of masculinization in rabbit females as the in utero proximity to male siblings. Our results suggest that the IUP effects may have similar physiological bases across different mammalian taxa including Lagomorphs.

Maternal gestational androgen levels in female marmosets (Callithrix geoffroyi) vary across trimesters but do not vary with the sex ratio of litters

Maternal hormones can dramatically modify offspring phenotypes via organizational actions on morphological and behavioral development. In placental mammals, there is the possibility that some portion of hormones in maternal circulation may be derived from fetal origin. We tested the possibility that maternal androgens in pregnant female marmosets reflected, in part, contributions from male fetuses by comparing levels of urinary androgens across pregnancy in females carrying varying numbers of male offspring. We monitored urinary androgen excretion in 18 pregnancies from five female white-faced marmosets (Callithrix geoffroyi). Androgen levels rose significantly in the first trimester of pregnancy, reached a peak in the middle of the second trimester, and then declined gradually until parturition. At no point in pregnancy were levels of urinary androgens higher in females carrying litters that had 50% or more males than in females carrying litters that were less than 50% male. Levels of maternal androgens were not associated with litter size, the number of males in the litter, or with the proportion of the litter that was male. The high levels of androgen in pregnant females are therefore likely of strictly maternal origin, and any modification of fetal growth and development can be considered a 'maternal effect'.

Beyond parity: association of ovarian cancer with length of gestation and offspring characteristics

Women with higher parity have a lower risk of ovarian cancer possibly because of pregnancy hormones, but the specific effect of different pregnancy hormones on ovarian cancer risk is not clear. Some clarification might be gained by considering situations where hormone levels vary between pregnancies. Study participants from an Australian population-based, case-control study of epithelial ovarian cancer (2001-2005) completed a reproductive/lifestyle questionnaire. The authors included 1,203 cases and 1,286 controls with at least 1 birth and, using multiple logistic regression, calculated odds ratios and 95% confidence intervals to investigate the effects of pregnancy-related factors on cancer risk. Women who had 1 or more preterm births had higher risks of ovarian cancer than those who had only full-term births (odds ratio (OR) = 1.48, 95% confidence interval (CI): 1.02, 2.15). The authors also found that bearing only boys was associated with a 2-fold increased risk of mucinous ovarian cancer (OR = 2.19, 95% CI: 1.15, 4.17). There was no association between multiple pregnancy and ovarian cancer (for any multiple pregnancy vs. only singleton pregnancies: OR = 1.22, 95% CI: 0.74, 2.02). The results suggest that pregnancies associated with differing hormonal milieux have different effects on ovarian cancer risk and that some of these associations may vary with histologic subtype.

Traces of embryogenesis are the same in monozygotic and dizygotic twins: not compatible with double ovulation

Common knowledge of over a century has it that monozygotic and dizygotic twinning events occur by unrelated mechanisms: monozygotic twinning 'splits' embryos, producing anomalously re-arranged embryogenic asymmetries; dizygotic twinning begins with independent ovulations yielding undisturbed parallel embryogeneses with no expectation of departures from singleton outcomes. The anomalies statistically associated with twin births are due to the re-arranged embryos of the monozygotics. Common knowledge further requires that dizygotic pairs are dichorionic; monochorionicity is exclusive to monozygotic pairs. These are fundamental certainties in the literature of twin biology. Multiple observations contradict those common knowledge understandings. The double ovulation hypothesis of dizygotic twinning is untenable. Girl-boy twins differ subtly from all other humans of either sex, absolutely not representative of all dizygotics. Embryogenesis of dizygotic twins differs from singleton development at least as much as monozygotic embryogenesis does, and in the same ways, and the differences between singletons and twins of both zygosities represent a coherent system of re-arranged embryogenic asymmetries. Dizygotic twinning and monozygotic twinning have the same list of consequences of anomalous embryogenesis. Those include an unignorable fraction of dizygotic pairs that are in fact monochorionic, plus many more sharing co-twins' cells in tissues other than a common chorion. The idea that monozygotic and dizygotic twinning events arise from the same embryogenic mechanism is the only plausible hypothesis that might explain all of the observations.

Prevalence of polycystic ovary syndrome in women from opposite-sex twin pairs

INTRODUCTION

Intrauterine androgens of a male fetus may influence the female fetus in opposite-sex twin pairs. Because female intrauterine overexposure to androgens could lead to polycystic ovary syndrome (PCOS), the prevalence of PCOS should be higher in women from opposite-sex twin pairs. Therefore, the aim of the current study was to evaluate the prevalence of PCOS in women from opposite-sex twin pairs compared to women from same-sex twin pairs, sisters, and female spouses of twins.

SUBJECTS AND METHODS

Data from 1325 monozygotic twins, 1191 dizygotic twins (711 women from same-sex twin pairs and 480 women from opposite-sex twin pairs), 745 sisters of twins, and 218 spouses of male twins were evaluated. PCOS was defined as less than nine natural menstrual cycles a year combined with either hirsutism or acne. The prevalence of PCOS was compared using a chi2 test. Binary logistic regression analyses were conducted to test for confounding effects of smoking, age, and body mass index.

RESULTS

No significant differences in PCOS prevalence were found between women from same-sex twin pairs (either monozygotic or dizygotic), opposite-sex twin pairs, sisters, and spouses.

CONCLUSION

The prevalence of PCOS is not different in women from opposite-sex and same-sex twin pairs, singleton sisters, or spouses. This indicates that possible androgen exposure of the female fetus, caused by a shared intrauterine environment with a male fetus, does not result in PCOS-like traits.

Does having a twin brother make for a bigger brain?

OBJECTIVE

Brain volume of boys is larger than that of girls by approximately 10%. Prenatal exposure to testosterone has been suggested in the masculinization of the brain. For example, in litter-bearing mammals intrauterine position increases prenatal testosterone exposure through adjacent male fetuses, resulting in masculinization of brain morphology.

DESIGN

The influence of intrauterine presence of a male co-twin on masculinization of human brain volume was studied in 9-year old twins.

METHODS

Magnetic resonance imaging brain scans, current testosterone, and estradiol levels were acquired from four groups of dizygotic (DZ) twins: boys from same-sex twin-pairs (SSM), boys from opposite-sex twin-pairs (OSM), girls from opposite-sex twin-pairs (OSF), and girls from same-sex twin-pairs (SSF; n=119 individuals). Data on total brain, cerebellum, gray and white matter volumes were examined.

RESULTS

Irrespective of their own sex, children with a male co-twin as compared to children with a female co-twin had larger total brain (+2.5%) and cerebellum (+5.5%) volumes. SSM, purportedly exposed to the highest prenatal testosterone levels, were found to have the largest volumes, followed by OSM, OSF and SSF children. Birth weight partly explained the effect on brain volumes. Current testosterone and estradiol levels did not account for the volumetric brain differences. However, the effects observed in children did not replicate in adult twins.

CONCLUSIONS

Our study indicates that sharing the uterus with a DZ twin brother increases total brain volume in 9-year olds. The effect may be transient and limited to a critical period in childhood.

The use of digit ratios as markers for perinatal androgen action

Since the ratio of the second-to-fourth finger length was first proposed as a marker for prenatal androgen action in 1998, over 100 studies have been published that have either further tested the association between the digit ratio and prenatal androgens, or employed digit ratios as a marker to investigate the association between prenatal androgens and a variety of outcomes, including behavior, fertility, and disease risks. Despite the clear demand for an adult marker of prenatal androgen action and increased use of digit ratios as such a marker, its validity remains controversial. This review (1) evaluates current evidence for the relationship between digit ratios and prenatal androgens (using experimentation with animal models, amniotic testosterone, and congenital adrenal hyperplasia case-control studies), (2) describes opportunities for future validation tests, and (3) compares the potential advantages and disadvantages of digit ratio measures with more established methods for studying the effects of prenatal androgens.