All Fetuses Are Not Equal: Spatial and Developmental Determinants of Within-Litter Variation in the Pig
In brief
Crowding, uterine position and fetal sex shape piglet growth before birth
This review describes how limited space and nutrients in larger litters, a fetus's position in the uterus, and fetal sex can contribute to growth differences even among piglets in the same pregnancy. Those differences can affect birth weight, survival and later performance, but the review does not quantify their effects or establish which factors matter most.
- Journal
- Reproduction & fertility (Q1)
- Published
- 3 November 2026
- Study design
- Narrative review / expert opinion
- Evidence level
- Level 5, Expert Opinion (CEBM 5)
- Authors
- Yvette E Wolpo, Claire Stenhouse
- PMID
- 42976092
- DOI
- 10.1530/RAF-26-0111
Why clinicians should know about it
- Picked for Embryology (paper of the day, 4 November 2026): Review of prenatal growth variation and developmental determinants
Abstract
In pigs, not all piglets grow the same before birth, even when they develop in the same pregnancy. However, these differences are often overlooked. This review describes some of the reasons why piglets within a litter can grow differently. As litter size increases, piglets must share limited space and nutrients in the uterus, creating competition during development. Differences can begin very early in pregnancy and may depend on where each fetus is located in the uterus. The sex of the fetus and neighboring fetuses may also influence growth and development. Together, these factors mean that each fetus develops under different conditions, which can affect birth weight, survival, and later performance. Understanding why these differences occur may help identify ways to produce more uniform litters and improve piglet survival and productivity.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.