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
Weight (g)
Weight (g)
1 -1
0 -18

        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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