The relative maturity, alertness, and reactivity of an infant at birth are sensitive indices of the neonate's health, the quality of the pregnancy, and the mother's wellbeing. Even when fetal growth and gestation length have been normal, the maturing fetus can still be adversely impacted by both physical events and psychological challenges to the mother during the prenatal period. The following research evaluated 413 rhesus monkeys from 7 different types of pregnancies to determine which conditions significantly influenced the behavioral responsiveness and state of the young infant. A standardized test battery modeled after the Neonatal Behavioral Assessment Scale for human newborns was employed. The largest impairments in orientation and increases in infant emotional reactivity were seen when female monkeys drank alcohol, even though consumed at only moderate levels during part of the pregnancy. The infants' ability to focus and attend to visual and auditory cues was also affected when the gravid female's adrenal hormones were transiently elevated for 2 weeks by ACTH administration. In addition, responses to tactile and vestibular stimulation were altered by both this ACTH treatment and psychological disturbance during gestation. Conversely, a 2-day course of antenatal corticosteroids 1 month before term resulted in infants with lower motor activity and reactivity. These findings highlight several pregnancy conditions that can affect a young infant's neurobehavioral status, even when otherwise healthy, and demonstrate that alterations or deficits are specific to the type of insult experienced by the mother and fetus.

The capacity of prenatal stress to disrupt the placental transfer of maternal antibody was evaluated in neonatal squirrel monkeys (Saimiri boliviensis peruviensis) gestated under different pregnancy conditions. Normal squirrel monkey offspring (n = 63) were compared with infants generated from pregnancies that involved either a single or 3 periods of disturbance (ns = 21 and 29, respectively). At parturition, levels of antibody (IgG) were determined in mothers and neonates. Only the chronic disturbance condition significantly altered antibody levels in the mothers, resulting in lower IgG. Antibody transfer to the fetus was also affected only by chronic disturbance. In this case the effect was bidirectional, influenced by the sex of the infant. Males were born with lower levels, whereas female infants actually had higher-than-normal IgG, despite lower titers in their mothers. Because virtually all IgG is derived from the prenatal transfer of maternal antibody, it indicates that the sex of the fetus differentially affected this placental process. The IgG receptor may have been up-regulated selectively on the placentas of female fetuses, compensating for reduced antibody in the disturbed mothers.

The concept of fetal programming is based on the idea that the developmental trajectory of infants is adjusted in response to in utero conditions. In species with extended parental care, these prenatally-derived tendencies are further substantiated by behavioral attributes of the mother during the postnatal period. We investigated the stability of maternal behavioral interactions with infant monkeys, and carefully varied prenatal conditions across siblings reared by the same mother. We hypothesized that effects of prenatal disturbance and the infant’s susceptibility would be differentially affected by maternal attributes. Hierarchical Linear Modeling was employed to analyze observational data on 121 rhesus macaques reared by a total of 35 multiparous mothers. A portion of the variance in 5 dyadic behaviors was statistically driven by the infant (or was unique to a particular mother-infant pair), but stable maternal propensities and a consistent style of care across siblings also substantially influenced behavioral interactions. Moreover, the magnitude and direction of the prenatal effects were contingent on a female’s intrinsic dispositions. When mothers typically exhibited high levels of a corresponding behavior, responsiveness to infants was enhanced as a consequence of prenatal disturbance. The opposite was true for less expressive females. Challenges to the wellbeing of pregnancy thus served to accentuate maternal predispositions and served to magnify the range of variation in mother-infant behavior across the whole population.

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