İnsan plasentasının morfometrisi: plasental parametrelerin karşılaştırılması

PDF Dosyası: 

arastirmax_2204_pp_153-156.pdf

Introduction
The placenta is a unique characteristic of the higher
mammals. In humans it is a thick mass, about 18 cm in
diameter. The placenta is attached to the uterus, and the
fetus is connected to the placenta via the umbilical cord.
The human placenta is the functional center of the
maternal-fetal system, and is responsible for respiratory,
nutritional, excretory, endocrine and immunological
functions.
Researchers have, for a long time, emphasized the
benefits associated with the anatomical examination of
the placenta. The literature presents several studies on
the morphology of placenta (1,2).
In this study, we aimed to investigate the relationship
between morphometric characteristics of human placenta and maternal-neonatal parameters. The placental
and umbilical cord morphologies in relation with some
maternal and fetal characteristics were evaluated.
Material and Methods
We performed this descriptive study on 259 human
placentas between April 2004 and November 2006. The
placentas were obtained from mothers who gave birth
at the Turkish Ministry of Health Ankara Etlik
* Maternity and Women's Health Academic and Research Hospital,
Turkish Ministry of Health, Etlik, Ankara
**Department of Anatomy, Gülhane Military Medical Academy
Reprint request: Dr. Necdet Kocabýyýk, Department of Anatomy,
Gülhane Military Medical Academy, Etlik-06018, Ankara, Turkey
E-mail: nkocabiyik@gata.edu.tr
Date submitted: January 30, 2007
Accepted: July 23, 2007
ARAÞTIRMA/ORIGINAL ARTICLE Gülhane Týp Dergisi 2007; 49: 153-156
© Gülhane Askeri Týp Akademisi 2007
Summary
We aimed to investigate the relationships between maternal-neonatal parameters and morphometric characteristics
of human placenta. We performed this study on 259 human
placentas. We observed that 257 placentas were single and
two (0.8%) were twin. Number of cotyledon was 16±2.22.
The length of umbilical cord was 57.13±9.08 cm. The cord
coiling was 0.18±0.1 per cm. Two out of 259 (0.8%) placentas had knotted umbilical cords. In most of the cases, there
were two umbilical arteries and one umbilical vein. In two
cases (0.8%), the artery was single. Diameters of umbilical
artery and umbilical vein were 2.48±0.38 mm and 2.97±0.49
mm, respectively. We compared the number of cotyledon
and hypercoiling of the cord. The differences between
them were statistically significant. In addition, there were
significant correlations between hypercoiling of the cord,
and abortion and APGAR scores.
Key words: Cotyledon, fetal demise, human placenta, morphometry, umbilical cord
Özet
Ýnsan plasentasýnýn morfometrisi: plasental parametrelerin karþýlaþtýrýlmasý
Bu çalýþmada maternal-neonatal parametreler ile insan
plasentasýnýn morfometrik karakteristikleri arasýndaki iliþ-
kilerin araþtýrýlmasý amaçlandý. Çalýþma 259 insan plasentasý
üzerinde gerçekleþtirildi. Çalýþmada 257 tek plasenta ve iki
adet ikiz plasenta tespit edildi. Kotiledon sayýsý 16±2.22 idi.
Umbilikal kordun uzunluðu 57.13±9.08 cm olarak ölçüldü.
"Cord coiling index" (her cm baþýna düþen korddaki kývrým
sayýsý) 0.18±0.1 cm olarak hesaplandý. Ýki yüz elli dokuz
plasentanýn ikisinde (%0.8) düðümlü umbilikal kord vardý.
Vakalarýn çoðunda umbilikal arter sayýsý iki, ven sayýsý bir
olarak bulundu. Ýki vakada ise sadece bir arter vardý.
Umbilikal arter ve ven çaplarý sýrasýyla 2.48±0.38 mm ve
2.97±0.49 mm olarak bulundu. Plasentalarýn kotiledon
sayýsý ve kývrýmlýlýk derecesini karþýlaþtýrdýðýmýzda, aralarýndaki farklýlýklar istatistiksel olarak anlamlý bulundu. Ek
olarak, kývrýmlýlýk derecesiyle düþük sayýsý ve APGAR skoru
arasýnda anlamlý korelasyonlar bulundu.
Anahtar kelimeler: Kotiledon, fetal ölüm, insan plasentasý,
morfometri, umbilikal kord154 · Eylül 2007 · Gülhane TD Karadeniz ve ark.
Maternity and Women's Health Academic and Research
Hospital, and they were transferred to the Department
of Anatomy of Gulhane Military Medical Academy. All
were transported within 10% formalin solution. Apgar
scores at 1 and 5 minutes after delivery (AI and AV)
were recorded. Mothers' age range was 17-42 years.
After removing the excess blood and membrane the
placentas were examined macroscopically and the
umbilical cords were cut at 1 cm from the placental
disc. Afterwards, placentas were fixed in 10% formalin
solution for an average period of seven days.
Number of cotyledon (NC), number of umbilical
artery (NUA) and number of umbilical vein (NUV)
were determined. The umbilical cord coiling index
(UCI) was calculated as the number of coils divided by
the sample length in cm. Diameter of umbilical artery
(DUA), diameter of umbilical vein (DUV), length of
umbilical cord (LUC) were measured with Vernier caliber in the Anatomy Dissection Laboratory of Gulhane
Military Medical Academy. Additionally, mothers and
newborns were evaluated according to maternal (age,
gestational age, height and weight) and neonatal (sex,
height and weight) parameters.
Statistical analysis was performed by using SPSS 10.0
(SPSSFW, SPSS Inc., Chicago, IL.,USA) statistical software. Descriptives of the parameters were given as
mean±SD notation. Kendall's tau-b or Spearman ranks
correlation of coefficients were calculated. P values less
than 0.05 were assumed as statistically significant.
Results
We found that 1 out of 259 placentas (0.4%) was
monochorionic monoamniotic twin placenta and 1 out
of 259 placentas (0.4%) was dichorionic diamniotic
twin placenta (Figure 1). The number of cotyledon was
16±2.22.
The length of umbilical cord was 57.13±9.08 cm
(range 22-76 cm). The distribution of cord coiling in
259 placentas was 0.18±0.1 per cm. Hypercoiling of the
cord was 0.34±0.38 (10.8%), and 2 out of 259 (0.8%)
placentas had knotted umbilical cords (Figure 2).
Number of umbilical artery was two and of umbilical vein was one in most cases. In two cases (0.8%), the
artery was single. We found the diameter of umbilical
artery as 2.48±0.38 mm, diameter of umbilical vein as
2.97±0.49 mm. In the two-vessel cord (single umbilical
artery and single umbilical vein), the blood flow to the
placenta is only through the single umbilical artery,
resulting in a compensatory increase of the arterial
diameter (Figure 3B).
The differences between number of cotyledon and
hypercoiling of the cord (p<0.001) and the differences
between APGAR scores (first and five minute) were
statistically significant (Table I). Moreover, there were
significant correlations between hypercoiling of the
Figure 1. Dichorionic diamniotic twin placenta cord, and abortion and APGAR scores (first minute).
Figure 2. A knotted (k) in an umbilical cord
Figure 3. Schematic representation of the umbilical cord transvers section. A: a normal three-vessel cord. a: umbilical artery,
v: umbilical vein. B: a two-vessel cordCilt 49 · Sayý 3 · Gülhane TD Morphometry of placenta · 155
Discussion
The human placenta is initially labyrinthine as the
early villous stems are formed, but becomes secondarily villous with the development of generation of terminal villi. The expelled placenta is a flattened discoidal
mass with an approximately circular or oval outline (3).
Approximately 30% of multiple gestations are
monozygous and 70% are dizygous. All dizygous twins
have dichorionic-diamniotic placentas. The separate
dichorionic placentas may occasionally be fused.
Monozygous pregnancies may have dichorionicdiamniotic (30%). Frequency of monozygous varies
from 1 in 30 births in Nigeria to 1 in 150 births in Japan
(4). We found that 1 out of 259 placenta was monochorionic monoamniotic twin placenta and 1 out of 259
was dichorionic diamniotic twin placenta.
Macroscopically, fetal surface of placenta is smooth,
shiny and transparent. The umbilical cord is usually
attached near the center of the fetal surface. The maternal surface is finely granular and mapped into some 15-
30 lobes by a series of fissures or grooves. The lobes are
often somewhat loosely termed cotyledons (3). We
observed 8-20 lobes. Cotyledons were counted from
maternal surface in order to evaluate their contribution
to oxygenization and function of the placenta.
The normal human umbilical cord measures approximately 55 cm at term. At term a cord shorter than 35
cm or longer than 85 cm is considered to be abnormal.
Both short and long cords may be associated with
intrauterine problems. A cord less than about 32 cm
may increase the likelihood of placental abruption.
Long cords may increase the probability of cord entanglement, prolapse and true knot development (5). In
our study, the length of umbilical cord was 57.13±9.08
cm (range 22-76 cm).
Less commonly, but with potentially devastating consequences, the umbilical cord can become knotted. If
the knot is loose, fetal circulation is maintained.
However, if the knot is tightened, for example at the
time of fetal descent through the birth canal, the tightening knot can occlude the circulation between the placenta and fetus, resulting in an intrauterine demise (5).
We observed that 2 out of 259 placentas were consisting
of knotted umbilical cords.
In 1992, Naeye has reported that approximately 1%
of all umbilical cords contain only one artery rather
than the normal two (6). In 1995, Persutte and Hobbins
have found that this value was 2.0% (7). Fetuses with
single umbilical artery had significantly more chromosomal and other congenital anomalies (7). In our study
we found that 2 out of 259 (0.8%) placentas have only
one artery. The umbilical cord typically contains two
arteries and a single vein. If only one artery and one vein
are grossly visible, the fetal anomaly rate is nearly 50
percent (8). These anomalies may affect the cardiovascular, genitourinary or gastrointestinal systems, and
others as well (9,10).
The average diameter of human umbilical cord was
reported as 1.5 cm and the average circumference was
separately reported as 3.6 cm after birth (1). The umbilical vein and artery have been measured before and after
birth. At term, the typical umbilical cord is in a diameter of 2.0 to 2.5 cm (11). We measured external diameters of these vessels as in Reynold's study (12). We
found that the external diameter of umbilical artery was
2.48±0.38 mm and the external diameter of umbilical
vein was 2.97±0.49 mm.
Most umbilical cords show a twist. This coiling
probably provides greater strength while retaining necessary flexibility. Presumably, this coiling arises because
the longer umbilical vein twists around the umbilical
arteries. The only twist-associated process which seems
relevant to stillbirth is the absence of any coiling.
Various series have shown frequencies of 10-18% for
untwisted cords in stillborns. This does not mean that
lack of twisting is the cause of intrauterine death. In
fact, no one has any idea what the sequence of events is
in connecting untwisted cords and stillbirth (2,13,14).
We found significant differences between the number
of cotyledon and hypercoiling of the cord (p<0.001).
However, in 1997, Dado et al. reported no statistically
significant difference in umbilical venous flow between
coiled and non-coiled cords when external compression, twisting and longitudinal stretching were applied
to the cord segments (15). Published series of umbilical
cord coiling range from 0.19 to 0.44 coils/cm (16-20).
In 2000, Machin et al. reported abnormally coiled
cords among 1329 cases (20). Twenty one percent of
cords were overcoiled. Principal clinical correlations
Table I. Correlations among the parameters
_____________________________________________________
Parameters Number of Hypercoiling Apgar scores
cotyledons of the cord (first minute)
_____________________________________________________
Abortion τ 0.377 0.171 0.095
p <0.001 <0.001 0.065
Number of τ 0.250 0.026
cotyledons p <0.001 0.634
Hypercoiling τ 0.250 0.001
of the cord p <0.001 <0.001
Apgar scores τ -0.029 0.113 0.244
(first minute) p 0.579 0.045 0.968
_____________________________________________________
τ: correlation coefficent156 · Eylül 2007 · Gülhane TD Karadeniz ve ark.
found in overcoiled cords were fetal demise (37%), fetal
intolerance to labor (14%), intrauterine growth retardation (10%), and chorioamnionitis (10%). Abnormal
cord coiling was associated with thrombosis of chorionic plate vessels, umbilical venous thrombosis, and cord
stenosis (20).
The normal umbilical cord coiling index (UCI) is
0.17 (+/-0.009) spirals completed per cm. Abnormal
cord coiling, i.e. UCI <10th centile (<0.07) or >90th
centile (>0.30) is associated with adverse pregnancy
outcome (21). We found that the distribution of umbilical cord coiling index in 259 placentas was 0.18±0.1
per cm and hypercoiling of the cord was 0.34±0.38
(10.8%).
In our study, noticeably, the differences between the
number of cotyledon and hypercoiling of the cord and
the differences between other parameters were statistically notable.
Finally, hypercoiling of the cord, hypocoiling of the
cord, abnormal cord insertion, knotted of the cord or
long umbilical cord and oligohydramnios may lead to
hypoxia or death of the fetus. Besides, small diameter of
umbilical arteries and vein can decrease in oxygen and
nutrition transfer capacity between the fetus and placenta.