American College of Nurse-Midwives

Workshop #23: The Placenta: To Know Me Is To Love Me
May 12th, 2000
Anchorage, Alaska

During the workshop, questions were asked regarding umbilical cord coiling, neonatal blood gases, umbilical vein as conduit for coronary artery bygass grafting, and RhoGam for RH incompatibility. Click here for the results of the MedLine search.

Below are the questions and answers for the quiz distributed during the workshop. (With page where answer can be found, in "The Placenta: To Know Me Is To Love Me" textbook, unless otherwise specified)

    A. At term, the placenta usually weighs and measures:
  • 1. 400 grams, 18 x 18 x 3 cm
  • 2. 470 GRAMS, 20 x 20 x 2 CM (pg. 61)
  • 3. 550 grams, 24 x 20 x 1.4 cm
  • 4. 350 grams, 20 x 14 x 2 cm
    B. "Battledore" placenta refers to a:
  • 1. right twisted umbilical cord
  • 2. velamentously inserted umbilical cord
  • 3. MARGINALLY INSERTED UMBILICAL CORD (pg. 61)
  • 4. a cord that has been torn off the fetal surface during manual placental removal
    C. Match the following:
  • 1. Decidua vera: D - decidua in late pregnancy lining uterus and overlying membranes
  • 2. Decidua capsularis: B - decidua attached to the membranes
  • 3. Decidua parietalis: C - decidua lining the uterus
  • 4. Decidua basalis: A - decidua underlying the placenta (pg. 70)
    D. The placenta may be green due to:
  • 1. prenatal meconium discharge
  • 2. hemosiderin pigment associated with old hemorrhage
  • 3. severe ascending infections
  • 4. ALL OF THE ABOVE (pg. 40)
    E. There are twice as many veins as arteries on the fetal surface of the placenta.
  • True or FALSE (pg. 72)
    F. Right twisted umbilical cords out number left twisted umbilical cords because more people are right handed.
  • True or FALSE (pg. 62)
    G. Under which circumstances is the Wharton's jelly more likely to be shrunken, contracted (lesser diameter umbilical cord)? (circle all that apply)
  • 1. with preterm delivery
  • 2. AT TERM (pg. 61)
  • 3. POSTDATES
  • 4. in association with polyhydramnios
  • 5. IN ASSOCIATION WITH OLIGOHYDRAMNIOS
    H. Single umbilical artery (SUA/two vessel umbilical cord), is most often associated with which of the following congenital anomalies?
  • 1. tracheo-esophageal fistula
  • 2. sirenomelia
  • 3. renal dysplasia or agenesis
  • 4. OVER 100 MALFORMATIONS ARE ASSOCIATED WITH SUA; NO ONE ANOMALY PREDOMINATES (pg. 66)
    I. Candida/yeast infection is easily identified on the umbilical cord.
  • TRUE or False (pg. 65)
    J. Which of the following is true?
  • 1. meconium may be discharged in response to fetal distress
  • 2. meconium may not be discharged in response to fetal distress
  • 3. meconium is thought to be a contributing cause to the development of cerebral palsy
  • 4. ALL OF THE ABOVE (pp. 158-159)
    K. Which of the following is not true of abruptio placentae?
  • 1. THE PLACENTAL PARENCHYMA IS TORN AND FRAGMENTED AT THE SITE OF ABRUPTION (pp. 3, 81)
  • 2. the placental maternal surface may show nothing
  • 3. the placental maternal surface may show adherent rubbery red to stringy brown blood clot
  • 4. is often due to damaged endometrial spiral artery
  • 5. the placental parenchyma overlying the abruption often infarcts
    L. Which of the following is not true of nicotine and cocaine? They are both:
  • 1. anorexic drugs
  • 2. vasoconstrictors
  • 3. associated with a higher incidence of abruptio placentae
  • 4. RESPONSIBLE FOR DOUBLING PROPORTION OF LOW BIRTH WEIGHT BABIES IN A POPULATION (Slotkin)
  • 5. associated with higher incidence of risky behavior (co-abuse of other drugs, no prenatal care, low socioeconomic status)
    M. Placental triage is an important part of health care for the child, mother and future children.
  • TRUE or False (pg. 52)
    N. Examination of the placenta may impact cases of birth injury litigation.
  • TRUE or False (pg. 157)
    O. The placenta is not a messy specimen to examine.
  • True or FALSE

References

  1. Schuler-Maloney D, Lee S: The Placenta: To Know Me Is To Love Me. A reference guide for gross placental examination, published 1998 by DSM PathWorks, Inc., St. Mary's, IA
  2. Slotkin TA: Fetal Nicotine or Cocaine Exposure: Which one is worse? Journal of Pharmacology and Experimental Therapeutics, 1998, Vol. 285, No. 3, pp. 931-945.

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These questions were asked during the workshop. MedLine reference review follows each question.

Q. Review the work of Dr. Thomas Strong, concerning umbilical cord twisting and fetal outcome.

A. Umbilical cord twisting is believed to be related, at least in part, to fetal activity. Therefore, with a more active fetus, a more twisted umbilical cord is expected and conversely, with a more sedate fetus, a poorly twisted cord is expected. (1)

In the early 1990's, Dr. Strong and his colleagues attempted to quantify this relationship, by first confirming what others had observed, that a child born with non-coiled umbilical vessels is at increased risk for perinatal morbidity and mortality (2). They then developed the "umbilical cord index" (divide the total number of complete vascular coils by the length in centimeters of the umbilical cord) (3) to quantitate umbilical vascular coiling, revealing the mean umbilical coiling index to be 0.21 +/- 0.07 (SD) coils per centimeter.

Dr. Strong et al discovered an association between increased incidence of abnormal karyotype, meconium staining and need for operative intervention for fetal distress and umbilical coiling index below 0.10, and that moderate to severe variable fetal heart rate decelerations were associated with both decreased umbilical coiling index below 0.10 and above 0.30.

If the umbilical coiling index was to be of clinical value, Dr. Strong recognized the importance of being able to determine cord coiling antepartum. By studying prenatal ultrasounds, he discovered that although 30% of noncoiled cords early in gestation will become coiled by delivery, the 2-6% of cords that remain uncoiled throughout gestation can be recognized on ultrasound, and may represent a real risk for suboptimal perinatal outcome. Dr. Strong et al also discovered that cords with umbilical coiling indices of less than 0.10 were at greater risk for nuchal entanglement. (5)

These 4 articles (2, 3, 4, 5) also discuss the fiber structure of the cord, the possible etiology of umbilical cord twisting and the possible protective function of the coiled cord.


Q. Which is really better for evaluating neonatal blood gases immediately? Blood from the umbilical artery or umbilical vein?

A. In their straight forward and succinct article, Dr. James Thorp and Dr. R Scott Rushing (6) review "the issues surrounding the use of umbilical blood gas analysis, including pertinent acid-base physiology, techniques, normal value, perinatal factors affecting the values, and controversies surrounding universal and selective sampling strategies."

"Which Umbilical Vessel Should Be Sampled?" suggests umbilical artery blood most accurately reflects the condition of the fetus, because it is the blood returning from the fetus versus the umbilical vein which carries the blood from the placenta to the fetus. However, umbilical venous blood gas measurements better reflect maternal acid-base status and placental function, in addition to fetal acid-base status. If only one vessel can be sampled, it should be the umbilical artery; however sampling from both an artery and the vein may be associated with some advantages, perhaps providing insights into the cause of an acid-base disturbance.


Q. What is the latest about using umbilical vein as a conduit for coronary artery bypass grafting?

A. Dr. Charles Canver, in his 1995 article "Conduit Options in Coronary Artery Bypass Surgery" (7), reported that although glutaraldehyde preserved umbilical vein grafts are well suited to withstand high arterial pressures and wall tension because of their circumferential elasticity and are readily available and easily stored, their usefulness as a coronary artery bypass graft is somewhat limited due to 1) the fact it remains a foreign material despite glutaraldehyde fixation which alters its immunogenicity; 2) dissection of the innermost layer of the vein occurs easily; and 3) the patency rate is low, with short-term patency of only 50%.

However, "the umbilical vein graft has become an effective alternative to autogenous material" for lower extremity revascularization, allowing limb salvage rates of up to 68% for crural reconstruction and 80% for popliteal reconstruction, according to Kurt Wengerter and Herbert Dardik. (8)


Q. With an Rh- Mom, why is RhoGam given with a miscarriage before the 20th week of pregnancy, if the fetus doesn't really begin to produce quantities of Rh+ red blood cells until about 20 weeks gestation?

A. According to the 1998 PDR (9), for Ortho Diagnostics MICRhoGAM (50 micrograms) and RhoGam (300 micrograms) and Bayer Corporation's BAYRHO-D Mini-Dose (50 micrograms) and BAYRHO-D Full Dose (300 micrograms), a lesser dose (50 micrograms versus the full dose of 300 micrograms) of Rho(D) immune globulin is given after a spontaneous or induced abortion, termination, or ectopic pregnancy up to and including 12 weeks gestation, to prevent isoimmunization in the event fetal-maternal/transplacental hemorrhage of greater than 0.1 ml of fetal red blood cells into the maternal circulation occurred at that time. Even though fetal red blood cell production is not well developed until about 20 weeks gestation, fetal red blood cells are present from early gestation. Although the total fetal red blood cell volume before 12 weeks is estimated to be less than 2.5 ml, there is a 3% risk of maternal isoimmunization. After 12 weeks gestation, regardless of the indications, a full dose of Rho(D) immune globulin is required.

References

  1. Schuler-Maloney D, Lee S: The Placenta: To Know Me Is To Love Me. A reference guide for gross placental examination. DSM PathWorks, Inc., St. Mary's, Iowa, 1998.
  2. Strong TH, Elliot JP, Radin TG: Non-coiled Umbilical Blood Vessels: A new marker for the fetus at risk; Obstetr & Gynecol, March 1993; 81 (3): 409-411.
  3. Strong TH, Jarles DL, Vega JS, Feldman DB: The Umbilical Coiling Index; Am J Obstet Gynecol, January 1994; 170 (1): 29-32.
  4. Strong TH, Finberg HJ, Mattox JH: Antepartum Diagnosis of Noncoiled Umbilical Cords; Am J Obstet Gynecol, June 1994; 170 (6): 1729-1733.
  5. Strong TH, Manriquez-Gilpin MP, Gilpin BG: Umbilical Vascular Coiling and Nuchal Entanglement; J Maternal-Fetal Med, 1996; 5: 359-361.
  6. Thorp JA, rushing RS: Umbilical Cord Blood Gas Analysis; Obstetr Gynecol Clin N Am, December 1999; 26 (4): 695-709.
  7. Canver CC: Conduit Options in Coronary Artery Bypass Surgery; Chest, October 1995; 108 (4): 1150-1155.
  8. Wengerter K, Dardik H: Biological Vascular Grafts; Sem Vasc Surg, March 1999; 12 (1): 46-51.
  9. Physician's Desk Reference, 1998, Medical Economics company; pp.: 641-643, 1981-1982.