The idea that human males are most strongly attracted to traits that peak in women in the nubile age group raises the question of how well women in that age group contend with the potential hazards of a first pregnancy. Using data for 1.7 million first births from 1990 U.S. natality and mortality records, we compared outcomes for women with first births (primiparas) aged 16–20 years (when first births typically occur in forager and subsistence groups) with those aged 21–25 years. The younger primiparas had a much lower risk of potentially life-threatening complications of labor and delivery and, when evolutionarily novel risk factors were controlled, fetuses which were significantly more likely to survive despite lower birth weights. Thus, nubile primiparas were more likely to have a successful reproductive outcome defined in an evolutionarily relevant way (an infant of normal birth weight and gestation, surviving to one year, and delivered without a medically necessary cesarean delivery). This suggests that prior to the widespread availability of surgical deliveries, men who mated with women in the nubile age group would have reaped the benefit of having a reproductive partner more likely to have a successful first pregnancy.

人类男性最容易被适婚年龄段女性的特征所吸引，这一观点提出了一个问题：该年龄段的女性如何应对第一次怀孕的潜在危险。我们使用 1990 年美国出生和死亡率记录中 170 万头胎的数据，比较了 16-20 岁头胎（初产妇）女性（头胎通常发生在采集群体和生存群体中）与 21-25 岁女性的结局。年轻的初产妇发生可能危及生命的分娩并发症的风险要低得多，并且当控制进化上新颖的风险因素时，尽管出生体重较低，胎儿的存活率却明显更高。因此，适龄初产妇更有可能获得以进化相关方式定义的成功生殖结果（正常出生体重和妊娠的婴儿，存活至一年，并且在没有医学上必要的剖腹产的情况下分娩）。这表明，在手术分娩广泛普及之前，与适婚年龄组女性交配的男性将受益于拥有更有可能成功首次怀孕的生殖伴侣。