At birth the cardiovascular system undergoes extensive remodelling under the changed haemodynamics of the now activated pulmonary system. In addition, umbilical vessels and vascular shunts are initially functionally closed and then eventually structurally (anatomically) closed. The remnants of some vessels remain in the adult as ligaments. This page gives a brief overview of some of these human neonatal vascular changes.
The heart at birth is anatomically higher and lies more transverse than seen in the adult, tilting of the heart occurs between 2 to 6 years of age.
A newborn infant
Page Links: Introduction | Reading | Umbilical Vasculature | Foramen Ovale | Ductus Arteriosus | Ductus Venosus | Glossary
The umbilical blood vessel cavity is lost postnatally over the course of weeks to months after birth.
The adult anatomical remnant of the umbilical vein between the umbilicus and liver is the ligamentum teres.
There are two separate forms of foramen ovale closure; functional and structural. Functional closure begins at the first breath and is rapid. Structural (anatomical) closure is much slower and generally occurs before the end of the first year.
The ductus arteriosus is a direct connection between the pulmonary trunk and the dorsal aorta. Postnatal closure occurs initially by by smooth muscle contraction and begins at the first breath and is rapid, completed within the first day (about 15 hr after birth). Anatomical closure is much slower occuring by 2–3 weeks after birth (33% of infants), by 2 months (90% of infants) and by 1 year (99% of infants).
The adult anatomical remnant of the ductus arteriosus is the ligamentum arteriosum.
The ductus venosus connects portal and umbilical blood to the inferior vena cava. Functional closure occurs postnatally within hours. Structural closure commences days after birth and completes by 18 to 20 days.
The adult anatomical remnant of the ductus venosus is the ligamentum venosum (a dorsal fissure on the liver).
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Birth or parturition is a critical stage in development, representing in mammals a transition from direct maternal support of fetal development, physical expulsion and establishment of the newborns own respiratory, circulatory and digestive systems.
This page introduces circulatory changes related to birth and the neonate and should give you a feel for the topic.
Note there is an additional page covering Postnatal Heart Development.
Please email Dr Mark Hill if you wish to make a comment about this current project.