Topic 8: Pregnancy Flashcards
(37 cards)
How much weight on average is gained during the first, second, and third trimesters?
Weight gain is relatively small during the first trimester (13 weeks) with a total gain of only 1–2 kg
Weight gain increases in the second and third trimesters with an average gain of around 0.4 kg per week.
What is weight gain comprised of?
In the first half of pregnancy, about 80% of weight gain is due to maternal tissues. In the final weeks of pregnancy, from 40 weeks, the fetus accounts for about a quarter of maternal weight gain. The remainder is largely due to an increase in maternal extracellular fluid. Overall water accounts for well over half of the maternal weight gained during a normal pregnancy.
In total, how much on average is recommended to gain throughout the pregnancy?
This is dependent on pre-pregnancy weight Pre-pregnancy BMI. Less than 18.5 kg/m² = 12½ to 18kg 18.5 to 24.9 kg/m² = 11½ to 16kg 25 to 29.9 kg/m² = 7 to 11½ kg Above 30 kg/m² = 5 to 9kg
What are the pregnancy complications for women who are over 120% of their normal body weight?
- hypertension,
- gestational diabetes
- postpartum hemorrhage
- caesarean section and
- a large for gestational age (LGA) infant who weighs more than 4000g. These LGA infants are at risk of injury during delivery and higher neonatal mortality and morbidity.
Overweight and obese mothers are less likely to gain higher amounts of adipose tissue during pregnancy, true or false?
False
What are the two major roles of the placenta?
- the source of hormones that regulate both fetal and maternal metabolism during pregnancy.
- it provides the means whereby oxygen and nutrients are delivered to the fetus and waste products are removed
What is the role of progesterone in pregnancy?
- cause relaxation of the smooth muscles of the uterus so that it can expand as the fetus grows, also having a relaxing effect on other smooth muscles in the body.
- Relaxation of the muscles of the gastrointestinal tract reduces motility in the gut, allowing more time for nutrients to be absorbed.
- The slower movement is also a cause of constipation commonly experienced by pregnant women.
- More general metabolic effects of progesterone are to induce maternal fat deposition, reduce alveolar and arterial pCO2 (to facilitate the exchange of lung gases during respiration), and increase renal sodium excretion.
Which nutrients usually increase in pregnancy?
In contrast to water-soluble nutrients, fat-soluble nutrients generally increase with pregnancy, for example, triglycerides, cholesterol, and free fatty acids
What happens to respiration during pregnancy?
Maternal oxygen requirements increase due to increases in metabolic rate and tissue mass in the uterus and breasts. More efficient gas exchange in the alveoli increases the oxygen-carrying capacity of the blood.
What happens to gastrointestinal function during pregnancy?
Progesterone causes a decrease in tone and motility of smooth muscles of the gastrointestinal tract. This can result in delayed gastric emptying and reverse peristalsis, which can eventually lead to gastro-oesophageal reflux.
Another outcome is that absorption of nutrients from the small intestine increases. Water absorption from the colon also increases which can lead to constipation, and this is further exacerbated by the enlarging uterus on the gastrointestinal tract also making elimination difficult.
Other physiological changes include an increase in appetite, nausea, and vomiting, and alterations in the sense of taste.
What happens to metabolism during pregnancy?
Changes in carbohydrate, fat, and protein metabolism occur during gestation:
Fat becomes the major fuel source for the mother, sparing glucose for the fetus.
Glucose contributes 50–70% of fetal energy requirements during the last trimester. The rapid uptake of glucose by the fetus results in fasting blood glucose levels lower than that of non-pregnant women.
Placental estrogen and progesterone cause an increase in the storage of maternal body fat during the second trimester.
Lipolysis increases during the third trimester when fetal demands for glucose cause maternal plasma glucose levels to fall.
What happens to BMR during pregnancy?
Basal metabolic rate (BMR) usually rises by the fourth month of gestation and exceeds non-pregnant levels by 15–20% towards the end of gestation.
The increase in BMR reflects increases in maternal cardiac output dictated by increases in oxygen demands by the fetus and the additional energy necessary to support the growth of fetal and maternal tissue.
What has studies using doubly labeled water on pregnant women revealed about energy expenditure?
One of the most important findings is that inter-individual variability in the energy cost of pregnancy is very large, even within the same population.
What are three advantages of using doubly-labeled water to assess total energy expenditure?
1 - It can be applied to free-living individuals; that is, the subject need not be restrained or confined to bed.
2 - CO2 elimination is measured over a prolonged period, hours to days, and thus it includes a composite measure of energy consumption throughout the entire period.
3 - The method is simple and noninvasive. It requires administration of a single dose of labeled H2O and a few samples of urine, or saliva, or blood to be obtained to measure the changes in isotopic enrichment over several days. It can be used in adults, children, and infants with ease, without requiring any major modifications of equipment.
How is energy intake influenced by pregnancy?
The energy cost of pregnancy varies with the amount and composition of maternal and fetal tissues deposited. On average it is around 1175 kJ per day in women with a gestational weight gain of around 12kg.
What is the NRV’s for pregnant women’s energy intake?
The 2006 nutrient reference values (NRV) recommend an additional 1.4 MJ/day during the second trimester and 1.9 MJ/day during the third trimester. This can easily be provided by a piece of fruit and a small sandwich.
What is the NRV’s for protein in pregnant women?
The 2006 NRV for protein during pregnancy recommends:
- EAR: an additional 0.2 g/kg/day during the last two trimesters, resulting in an EAR of 0.8 g/kg/day during this state.
- RDI: estimated using a CV (coefficient of variation) of 12% giving an RDI in the second and third trimesters of 1.00 g/kg/day or 60 g/day.
When pregnancy occurs during adolescence, the requirements are slightly different:
- EAR: 0.82 g/kg/day
- RDI: 1.02 g/kg/day (corresponding to 58g/day)
What concerns are there around protein intake for pregnant women?
Both low protein and higher protein diets during pregnancy have been associated with detrimental effects on offspring. Excess protein intake during pregnancy is non-beneficial to the fetus and can in fact be harmful. Studies dating as early as the 1980s have demonstrated high protein intake during pregnancy (through a high protein diet or supplementation) is associated with higher preterm birth rates, reduced fetal growth, low birth weight, neonatal deaths, and higher blood pressure in later life.
What micronutrients are the exception to a necessary increase of intake during pregnancy?
Exceptions are potassium, sodium, calcium, and vitamin D.
What is the recommendation for Vitamin B12 during pregnancy and the reason for the increased intake?
2.6 µg (micrograms) per day, which is 0.2 µg per day higher than the recommendation for adult females. The extra vitamin B12 is required for the fetus and increases metabolic demand in the mother. This is pretty easy to achieve unless the mother is vegan, in which case she would need to supplement.
What is the recommendation for folate and its role during pregnancy?
Folate plays a critical role in cell division in DNA and RNA synthesis. The Australian Dietary Guidelines recommend a woman planning pregnancy and during the first three months of pregnancy require a daily 400ug (0.4mg) folic acid supplement in addition to foods naturally rich in folate.
What is the RDI of iron during pregnancy?
The 2006 RDI recommends 27 mg/day during pregnancy, which cannot generally be provided by diet alone, with supplements required to reach this level of intake.
Why have the Australian iron requirements in pregnancy been set at a level that appears to require iron supplementation?
Firstly, because anemia during pregnancy may compromise oxygen delivery to the fetus, and anemic women are less well able to tolerate obstetric complications during childbirth.
Secondly, the additional amount of iron required during pregnancy is greater than the iron stores of many women, which seldom exceed 500 mg and are less than 100 mg in a considerable proportion of the female population. The extra iron needed for a normal pregnancy, therefore, has to be provided mainly from external sources.
Why is there no additional increase of calcium needed?
Significant increases in maternal calcium accretion, bone turnover and intestinal absorption early in pregnancy prior to fetal bone mineralization have also been shown. These adaptations provide the minerals necessary for fetal growth without requiring an increase in maternal dietary intake or compromising long-term maternal bone health.
