The Sexually Dimorphic Nature of the Human Placenta: A Literature Review

Abstract

Introduction: Neonatal growth is dependent on the ability of the mother’s placenta to deliver nutrients. As such, placental health is an important aspect of obstetric care. Existing literature has suggested an association between fetal sex and placental growth and development; however, no centralized study has been conducted. This paper aims to conduct a narrative review that summarizes findings from published literature on the effects of fetal sex on the growth and development of the placenta through three facets: placental function, structure, and outcome.

Methods: Databases including Medline, Embase, and EMCare in Ovid, CINAHL, Web of Science, and Scopus were searched using keywords for the concepts of fetal sex and placenta. These were searched in combination with keywords relevant to placental function, placental structure, and pregnancy outcomes, using Boolean operators “OR/AND/NOT” as necessary. Studies written in English and published in peer reviewed journals were considered, with an emphasis on those published between 2017-2021.

Results: Sexual dimorphism is evident in the fetal responses to stressful maternal environmental conditions, onset by conditions such as asthma and obesity. Sex-specific differences have also been observed in complications of pregnancy, including gestational diabetes mellitus (GDM), preeclampsia, preterm delivery, stillbirth, and insufficient uteroplacental circulation.

Discussion: Despite the placentas from male and female births being categorized together in previous literature, this review highlights the sexually dimorphic nature of the ephemeral organ. Knowledge of fetal sex as early as possible during the pregnancy will help clinicians take proactive measures to optimize the health of the mother and the fetus.

Conclusion: This study provides a holistic review of the effects of placental development among the fetal sexes, a critical aspect to monitor for effective obstetric care. Hence, further research into the sexually dimorphic nature is warranted.