Immunization against the human platelet antigen (HPA)-1 alloantigen is the most common cause of severe fetal and neonatal thrombocytopenia. Fetal therapy has substantial risks and its indications need better definition. Of 24,417 consecutive pregnant women, 618 (2.5%) were HPA-1a negative of whom 385 entered an observational study. All were HLA-DRB3*0101 genotyped and screened for anti–HPA-1a. Their partners and neonates were HPA-1 genotyped and the latter were assessed by cord blood platelet counts and cerebral ultrasound scans. Anti–HPA-1a was detected in 46 of 387 pregnancies (12.0%; 95% CI 8.7%-15.2%). All but one were HLA-DRB3*0101 positive (odds ratio 140; 95% CI 19-1035;P< .00001). One baby died in utero, and of 26 HPA-1a–positive babies born to women with persistent antenatal antibodies, 9 were severely thrombocytopenic (8 with a count <10 × 109/L, 1 with a large porencephalic cyst), 10 were mildly thrombocytopenic, whereas 7 had normal platelet counts. Severe thrombocytopenia was significantly associated with a third trimester anti–HPA-1a titer ≥ 1:32 (P = .004), but was not observed in babies of women with either transient or postnatal-only antibodies. HPA-1a alloimmunization complicates 1 in 350 unselected pregnancies, resulting in severe thrombocytopenia in 1:1,200. HPA-1a and HLA-DRB3*0101 typing combined with anti–HPA-1a titration allows selection of the majority of pregnancies at risk of severe thrombocytopenia.

Studies of amniotic testosterone in humans suggest that fetal testosterone (fT) is related to specific (but not all) sexually dimorphic aspects of cognition and behaviour. It has also been suggested that autism may be an extreme manifestation of some male-typical traits, both in terms of cognition and neuroanatomy. In this paper, we examine the possibility of a link between autistic traits and fT levels measured in amniotic fluid during routine amniocentesis. Two instruments measuring number of autistic traits (the Childhood Autism Spectrum Test (CAST) and the Child Autism Spectrum Quotient (AQ-Child)) were completed by these women about their children (N=235), ages 6-10 years. Intelligence Quotient (IQ) was measured in a subset of these children (N=74). fT levels were positively associated with higher scores on the CAST and AQ-Child. This relationship was seen within sex as well as when the sexes were combined, suggesting this is an effect of fT rather than of sex per se. No relationships were found between overall IQ and the predictor variables, or between IQ and CAST or AQ-Child. These findings are consistent with the hypothesis that prenatal androgen exposure is related to children exhibiting more autistic traits. These results need to be followed up in a much larger sample to test if clinical cases of ASC have elevated fT.

Empathy involves an understanding of what others are thinking and feeling, and enables us to interact in the social world. According to the Empathizing-Systemizing (E-S) theory, females on average have a stronger drive to empathize than males. This sex difference may in part reflect developmental differences in brain structure and function, which are themselves under the influence of fetal testosterone (fT). Previous studies have found that fT is inversely correlated with social behaviors such as eye contact in infancy, peer relationships in preschoolers, and mentalistic interpretation of animate motion. Male fetuses are exposed to higher levels of testosterone than are female fetuses. The present study investigates empathizing in children, as a function of amniotic measures of fT. One hundred ninety-three mothers of children (100 males, 93 females) aged 6-8 years of age completed children's versions of the Empathy Quotient (EQ-C), and the children themselves were tested on "Reading the Mind in the Eyes" Task (Eyes-C). All mothers had had amniocentesis during the 2nd trimester of pregnancy. There was a significant negative correlation between fT and scores on both measures. While empathy may be influenced by post-natal experience, these results suggest that pre-natal biology also plays an important role, mediated by androgen effects in the brain. These results also have implications for the causes of disabilities involving empathy, such as autism spectrum conditions, and may explain the increased rate of such conditions among males.