Marginal and Velamentous Cord Insertions: A True Story of Abnormal Placental Cord Insertions
Did you know the umbilical cord can insert into the placenta in a variety of ways? To be perfectly honest, I had no idea these variations existed until my placenta and I became an abnormal statistic with Baby #4.
Before we dive into cord insertions, let’s quickly recap the cord itself. The umbilical cord connects the placenta to the baby (1). Three blood vessels (two arteries and one vein) are surrounded by a protective substance called Wharton’s Jelly (2). The vein supplies oxygen- and nutrient-rich blood to the developing baby while the two arteries return oxygen-poor blood back to the placenta. The umbilical cord is baby’s lifeline and if anything happens to these vessels in utero, the effects can be devastating.
Normally, the umbilical cord inserts into the center of the placenta (central insertion) or slightly off-center (eccentric insertion). In a 2017 meta-analysis, normal cord insertion occurs about 90% of the time. However, sometimes the cord inserts within 2 cm of the placenta edge called a marginal cord insertion (MCI) or not into the placenta at all which is called a velamentous cord insertion (VCI) (3). In the case of VCIs and my 4th birth experience, the umbilical cord inserts into the membranes of the amniotic sac where unprotected blood vessels run through the membranes before reaching the placenta edge. When the umbilical cord is supported by very little or no placental tissue, the risk of blood vessel abruption becomes much greater.
MCIs and VCIs are considered abnormal cord insertions and occur about 7% and 1% of the time, respectively. They occur more frequently in multiples pregnancies and are associated with spontaneous abortion, preterm labor, infants small for gestational age, vasa previa, emergency cesarean, and other adverse outcomes (3). Without the protection of Wharton’s Jelly, risk to these umbilical vessels is much greater, particularly in VCIs. That being said, MCIs have a tendency to become VCIs towards the end of pregnancy. The biggest risk of these abnormal cord insertions occurs if one of the exposed vessels ruptures, immediately compromising baby’s lifeline. This could happen naturally (during labor) or artificially (if a birth attendant ruptures the membranes).
Imagine our surprise when our homebirth midwife returned upstairs to the “birthing suite” to share that we had an undiagnosed velamentous cord insertion. Not only that, but the exposed blood vessels were very close to his head. His amniotic sac broke between two vessels allowing him to pass through without compromising his blood supply. Believe it or not, this is only the beginning of Clark’s miraculous, probably-shouldn’t-have-been-a-homebirth story. For the rest of the story check out the BIRTHFIT podcast or the BIRTHFIT Colorado blog.
One of the many things I love about BIRTHFIT is the intentional practice around all four pillars: fitness, nutrition, mindset, and connection. Over the past 5 years of working with BIRTHFIT, I became more educated and conscious of ways I could “stack the deck” in favor of optimal birth outcomes (read: improved my practice around the four pillars). My daily practice around the nutrition pillar, made intentional by the work of Lily Nichols, supported the building of a very strong amniotic sac which mitigated the increased risk of premature rupture. While the scientific community doesn’t fully understand why abnormal cord insertions occur, our lifestyle choices remain within our control and can buffer potential adverse outcomes.
Melissa HemphillBIRTHFIT Coach Seminar Director BIRTHFIT Colorado Regional Director @birthfit_colorado @melissahemphill
- Kliman, Harvey J. The Umbilical Cord, Yale University School of Medicine, 1998, web.archive.org/web/20130328143634/http://www.med.yale.edu/obgyn/kliman/placenta/articles/EOR_UC/Umbilical_Cord.html
- “Wharton’s Jelly.” Wikipedia, Wikimedia Foundation, 15 Jan. 2019, en.wikipedia.org/wiki/Wharton%27s_jelly.
- Ismail, Khadijah Irfah et al. “Abnormal placental cord insertion and adverse pregnancy outcomes: a systematic review and meta-analysis” Systematic reviews vol. 6,1 242. 6 Dec. 2017, doi:10.1186/s13643-017-0641-1