The ability if the terms to grow and
thrive in utero depends on the placental function and the average Wight of the
placental at term is 5089-the ratio between placenta weight and brim weight of
the new born is 1:6. However, methods of measurement vary widely particularly due
to differences in placental preparation.
Placental weight and its
relationship to infant size at birth have been studied for more her a century.
Past studies indicated that placental weight was associated with pregnancy
outcome. High placenta weight was associated with a poor placental outcome, a low
Apgar score, respiratory distress syndrome and placental death; where as a low
placental weight was associated with medical complications in the mother.
Barker et al reported that altered growth of the placental was a predictor of
maternal medical diseases including card oracular disease, hypertension and
diabetes mellitus. Other factors such as race and socio economic status also
affect the placental weight.
Careful examination of the placenta
can provide insight regarding the in utero-environment of the fetus before
delivery two standard references are endorsed by the college of American
pathologists absolute placental weight and fetal/ placental weight (F/P ratio)
have been documented. For example, small placentas may be associated with
trisomies, where as large placentas may be associated with maternal diabetes.
Disproportionately large placentas (low F/P ratio) could reflect acute placental
injury resulting in villous edema or a chronic process requiring placental over
growth, such as maternal anemia or malnutrition. Disproportionately small
placentas (high F/P ratio) may be seen in maternal hypertension, and may result
in fetal distress or low Apgar scores. Recent birth weight tables show fetal
birth weights at term have increased over time. There is a positive correlation
blow fetal birth weights and placental weights. The standard method of weight the
placental, after trimming the placental dist of membranes and umbilical card
may also merit simplification. Leary et al suggested that the fetal weight
placental weight correlation does not change when placentas are weight trimmed
compared to when they are weighed untrimmed. The placenta can be weighted with
membranes and cord attached but the standard approach since its proposal by
Benirschke in the early 1960s is to weight the placental after the extra
placental membranes and the umbilical cord are trimmed from the disk.
The Placenta
The placenta is the most important accessory fetal structure
that brings fetal and maternal circulation into close relationship morphologically
it is partly of fetal organ, the trophoblast, and partly of maternal origin,
the deciduas-the examination of placental (like atrasonography or chorionic
villa biopsy etc) is one of the common method of investigation for factors
endangering the fetus and newborn.
The human full term placental is a discord shaped organ
measuring 15-20cm in diameter, 1.5-3cm in thickness and weight ranging from 500
to 600gm it has two surfaces, a fetal surface and a maternal surface when
viewed from the maternal side 15-20 slightly bulging areas, “the cotyledons”
are recognizable these cotyledons are separated by grooves “the deudual septae”.
The fetal surface shoos large arteries and veins, “the umbilical vessels”
converging two and the umbilical cord and is covered by amnion.
Placenta weight
The delivered placenta is “deflated” compared to its
state in utero, a consideration for anyone attempting ultrasound or anatomic correlations.
The average diameter of the delivered placenta at term has reported as 18-5cm
(range 10-5 to 24.5cm), with a mean thickness of 2.3cm (range 1.1 to 4.1cm). The
same source descried the early growth of the placenta as primarily an increase
in diameter of the chorionic disc, while in the later stages of gestation,
placental weight increased primarily due to increase in placental thickness.
They likewise reported that mean diameters of the placenta at the third to six
months as 5.8cm 8.2cm, 10.8cm, and 13.0cm, respectively the number of major villous
trunks remains constant; therefore, placental growth requires that each major
trunk (established in the early months of gestation) must arborize or otherwise
develop proportional to the increase in placental weight from early gestation to
delivery. Schneider has recently reviewed the ultrasound data regarding placental
volume in the mid trimester. The mean increase in placental volume between 16
and 24 weeks was 31, - +, 8cm3; further placental volume in the
second trimester was dusty correlated with infant birm weight, suggesting that
mid trimester placental well being is an important determine of late fetal
grown.
Expected Fetal and Placental Weight
Ratio
|
Weeks
|
Placental
|
Fetal
|
F.P
|
|
Estuation
|
Weight (g)
|
Weight (g)
|
Ratio
|
|
8
|
6
|
1 -1
|
0 -18
|
|
10
|
14
|
5
|
0-36
|
|
12
|
26
|
17
|
0.65
|
|
14
|
42
|
30
|
0.71
|
|
16
|
65
|
60
|
0.92
|
|
18
|
90
|
130
|
1.44
|
|
20
|
115
|
250
|
2.17
|
Baby’s Weight
In first world nation the average weight of a
full-term newborn is approximately 3.4kg (7½ lbs), and is typically in the
range of 2.7-4.6kg (5.5-10 pounds) over the first 5-7 days following birth the
body weight of a term neonate decreases by 3% - 7% and is largely as a result
of the reasorbtion and urination of the fluid that initially fills the lungs,
in addition to a delay of often a few days before breast-feeding becomes
effective. After the first week healthy term neonates should gain 10-20
gram/kg/day.
Factors that determine the Birth weight
of a baby
·
Infant gender
·
Multiple factors
·
Size of the
parents
·
Birth order
·
Baby’s health
Maternal
factors such as race and ethnicity, nutrition and current and previous
pregnancy medical risk characteristics.
Mothers Weight
The pattern and amount of weight gain is closely associated
with gestational stages. Additional energy is required during pregnancy due do
the expansion of maternal tissues and stores in order to support fetal
development.
In the first trimester (blastogenesis and early embryonic
stages), the mother experiences animal weight gain (approximately
0.5-2kilograms), while the embryo weights only 6 gram, which is approximately 6
raisins.
In the second trimester and third trimester (late
embryonic and fetal stages the fetus undergoes rapid weight growth and the
weight increases to about 3000-4000 grams. It is also in this period that the
mother experiences the bulk of her gestational weight gain but the amount of
weight varies greatly the amount of weight gain depends strongly on their
pre-pregnant weight.
Generally, a normal weight is strongly recommended for
mothers when entering gestation, as it promotes overall both of infants.
Maternal body weight is determined by the body mass
index (BMI) which is defined as the weight in kilograms divided by the square
of the height in meters. While pregnant, body weight should be managed within the
recommended gestational weight gain range as it is shown to have a positive effect
on pregnancy outcomes.
Normal Weight Women
Women having a BMI of 18.5-24-9 are classified as
having a normal or healthy body weight. This group have the lowest risk of
adverse birth overcomes. Their babies are least likely to either be low-birth weight
or high –birth weight. It is advised that women with a normal weight before pregnancy
should gain a total of 11.5 kilograms to 16-0kilogram throughout gestation,
which is approximately 0.0 kilogram per week in the second and third trimesters.
In order to maintain a steady weight gain, the mother
should engage in mild physical activities participating in aerobic activates
such as walking and swimming 3 to 4 times a week is usually adequate. Vigorous physical
activity is not recommended since an excessive loss of calories is induced
which is not sufficient to support fetal development.
A proper diet is also essential to healthy weight gain
the common saying “a women is eating for two” often leads to mothers thinking
that they should eat twice as much.
In reality, only a small increase in caloric intake is needed to provide for
the fetus approximately 350 calories in the third trimester. Also healthy choices
should be emphasized for these extra calories such as whole grain products,
fruits and vegetables as well as low fat dairy alternatives.
Gain weight at a healthy rate
The rate at which you gain weight is carefully
monitored by your doctor. Gaining or losing a lot of weight in a short time can
be a sign of problems there are no set rules for the amount of weight to gain.
It varies from matter to mother and usually depends on the mother’s
pre-pregnancy weight and build. For mothers who were underweight before
pregnancy, the recommended rate of weight gain is about five pounds during the
first 13 weeks, and about a pound a week from then on. Total weight gain should
be 28 – 40 pounds
For normal weight mothers, the recommended weight gain
is three to five pounds during the first 13 weeks, then about a pound a week
from then on, for a total of 25 to 35 pounds. For over weight mothers, the
recommended weight gain is about two pounds during the first is weeks, and
about 2/3 of a pound per week from then on, for a total of 15 to 25 pound 5-
mothers under 52 “2” should gain 18 to 30 pounds. Teen mothers should gain 28
to 40 pounds. Mothers carrying twins should gain 35 to 45 pounds.
Your body begins getting ready for your baby by
storing fat. Most of this fat is stored in weeks 14 through 28 – almost no fat
is stored over your back, abdomen, and upper thighs; therefore the clothes you
were comfortable a fend weeks earlier may not fit even before you begin to
show. Fat is stored opposite the growth rate of your baby, which is minimal during
the first half of pregnancy and rapid during the last half. Stored fat provides
a reserve of calories for you and your baby to use in the last 10 to 12 weeks.
This is the time when your diet may not be able to keep up with the nutritional
needs of you and your baby.
Your weight should increase evenly. However, mothers
who gain too much too soon should not diet. Dieting can kept you from eating
enough Food to provide your baby with right nutrients. This can cause your baby
to grow and develop slower than normal. Instead of dieting, try controlling
your weight gain by cutting out sweets and fatty foods. If morning sickness
during the first few month caused you to lose weight or not gain the
recommended amount, “Catch up” to your recommended weight level once your
morning sickness stops. If you need advice about your diet ask your doctor to
recommend a nutritionist. The goal is to gain weight for you means an up and
down food supply for your baby.
Where the Weight Goes
Your baby makes up only part of your
total weight gain. A few founds become fat stores for energy needed during
labour, delivery, and breast feeders weight gain also comes from the extra
blood, muscles, fluids, and tissue your body makes for you and your baby to use
while you are pregnant. On average most women should gain a total of 25 to 30
pounds. The breakdown of weight gain is as follows:
Baby
7-8 pounds
Placenta
1 -2 pounds
Ammotic
fluid
Variation in Growth
Birth Weight: There
is much variation in growth of the fetus. When fetal size is less than
expected, that condition is known as infrauture growth restriction (IUGR) also called
fetal growth.
Factors affecting fetal
growth can be
·
Maternal
·
Placental or
fetal
Maternal factors include
·
Maternal weight,
body mass index, nutritional state, emotional stress, toxin exposure (including
tobacco, alcohol, heroin and other drugs which can also from the fetus in other
ways), and uterine blood flow
·
Placental factors
include: size, microstructure (densities and architecture) umbilical blood
flow, transporters and binding protein nutrient vitalization and nutrient
production
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