It’s common for women to get confused messages when it comes to exercising and nutrition during pregnancy. Many feel they are erring on the side of caution by giving up exercise altogether. Obviously there are many changes which occur during each trimester, so I’ve published the ‘client handbook’ we created for our clients who are considering pregnancy, are currently pregnant and/or breastfeeding. I hope this will help to clarify a few things…
Healthy and safe maternal weight gain
1st trimester: ~1-2kg
2nd and 3rd trimester: ~0.4kg/week
Recommended overall weight gain:
Starting at ‘normal’ weight (BMI 18.5-24.9): 11.5-16.0kg gain
Starting at ‘overweight’ (BMI 25.0-29.9): 7.0-11.5kg gain
Starting at ‘obese’ (BMI >30): 5-9kg gain
Components of maternal weight gain:
Up to 20 weeks:
Most weight gain due to increases in maternal tissues (eg: 80% of 4kg gain is maternal tissues)
Gain in weight of foetus accounts for ~50% of weight gained
Note: at the end of gestation….
- The placenta weighs around 500-700g
- The foetus approx. 3.5kgs
- Amniotic fluid – 1 litre
- Uterus increases to 1kg (50g pre-pregnancy)
- Blood volume increases by 40%
- Breasts – approx. 500g each
Function of extra stored fat
The majority of maternal fat gain during pregnancy is deposited on the abdomen, back and upper thighs. A certain amount of fat gain is necessary for the use of fuel for the mother in order to preserve glucose for the foetus. This results in lower blood sugar levels for pregnant women compared with pre-pregnancy. Stored fat is generally mobilised during post-partum period as a source of energy for lactation.
Underweight women have a higher risk of delivering small for gestational age infants. This risk can be decreased by gaining optimum weight during pregnancy. Energy intake required is approximately 150kjs per day higher than someone starting pregnancy at a ‘healthy’ weight.
Overweight women have a higher risk of gestational diabetes, hypertension, caesarean delivery and post-operative complications, as well as neural tube defects. If overweight at the beginning of pregnancy, a weight gain of <6kg is recommended. Weight loss during pregnancy is NOT recommended. A decrease in physical activity is another factor associated with a greater weight increase.
- Decrease in tone and motility of smooth muscles of the intestinal tract
- Delayed gastric emptying
- Increased absorption of nutrients
- Increased water absorption from the colon (constipation)
- Change in sense of taste
- Change in appetite
- Nausea and vomiting
Cardiovascular & renal function
- Increased cardiac output and blood flow through the kidneys
- Increased waste products from the foetus cleared through the kidneys
- Increased oxygen requirements often leading to breathlessness
- Changes in hormones (relaxin, progesterone, oestrogen and cortisol) cause a generalised increase in ligament and thus joint laxity. You may be at greater risk of injuring yourself if your exercise is not carefully monitored and adapted to suit your specific needs. This laxity causes and increase in available movement so it’s important to maintain strength throughout pregnancy. These hormones may remain elevated until 3-6 months after cessation of breastfeeding.
- Diastasis of Rectus Abdominus Muscle (DRAM) – This separation of the abdominal muscle is very common (66%) in the 3rd trimester of pregnancy.
What is ‘normal’?
<3-4cm separation (common – monitor closely)
>4cm separation (must be carefully managed by a specialist physiotherapist)
Benefits of controlled and monitored exercise
- Improves/maintains general health & wellbeing
- Improves cardiovascular fitness – important for stamina for labour, motherhood
- Weight-gain management – reducing the risk of gestational diabetes
- Reduces aches and pains
- Improves body awareness, posture and breathing
- Improves/maintains strength to counteract the effect of relaxin (laxity in joints/ligaments)
Core and pelvic floor muscles explained
While most think of the core as a tight six-pack or toned abs, however the most obvious abdominal muscles only form a small part of the core, which is actually a group of muscles that stabilise the spine and pelvis. Therefore, a core-strengthening exercise program needs to include all of these muscles to be effective. When well-conditioned, core muscles help to distribute the stresses of weight-bearing, as well as improving our balance and posture and reducing our risk of injury. During pregnancy, these muscles, along with your pelvic floor muscles, are subjected to increased pressure.
What are the core muscles?
While the definition of this group of muscles varies between experts, the following list includes the most commonly identified. Essentially core function can include additional muscles, such as the glutes (bottom), erector spinae (running from your neck to your lower back), the diaphragm and hip flexors, but for the purpose of this explanation I’ll stick with the primary group.
multifidus – located along the vertebral column, these muscles extend and rotate the spine
transverse abdominus (TVA) – located under the obliques, this is the deepest of the core muscles and wraps around your spine like a girdle for protection and stability
internal obliques – located beneath the external obliques
pelvic floor – This is a sling of muscle running from back to front, from the tail bone to the front of the pelvis. The pelvic floor muscles lift, while the deep abdominals draw in.
rectus abdominus – located on the front of the abdomen and referred to as a ‘six-pack’ when visible in lean individuals
external obliques – located on the side and front of the abdomen
Why are these muscles important?
Strong core muscles play such an important role in all movement that without conditioning, you’re almost certain to have poor posture and/or sustain an injury. It’s common for most women to become acutely aware of the importance of core strength during and post-pregnancy. Weak core and pelvic floor muscles can exacerbate bladder leakage, back pain and even the prolapse of internal organs. The pelvic floor muscles work as part of the core to regulate the internal pressure in the abdominal ‘cylinder’, in conjunction with the back and breathing muscles. During exercise the internal pressure within the abdomen is constantly changing. This regulation happens automatically for most people, however, if the core or pelvic muscles become weak, this may no longer work effectively. Ideally, the core muscles should work together with the pelvic floor ‘lifting’ and the abdominal and back muscles ‘drawing in’ to support the spine. However, when this is done incorrectly (and holding your breath), it causes excessive pressure to bear down on the pelvic floor resulting on strain on the bladder and bowel. If repeated, over time this can weaken ligaments and cause leakage or pelvic organ prolapse.
How do I activate my pelvic floor/core correctly?
We used to think that drawing the belly button towards the spine would activate our core, however, the latest research now indicates that this causes some to tighten their back muscles, draw in the abdomen and hold their breath. This places pressure down on the pelvic floor. To work effectively, the core muscles need to contract and relax throughout movement. Constant bracing can lead to stiffness in these muscles and can be as much of a culprit in ‘leakage’ as weak muscles.
The most familiar function that we all use pelvic floor muscles for is stopping ourselves from going to the bathroom. To correctly activate your core and pelvic floor, it’s easiest to feel if you lie down on your back and bend your knees with your feet flat on the floor. Place your fingers on the front of your hip bones and slide them inwards 2-3cms. To activate your pelvic floor muscles, think of stopping yourself from going to the bathroom. You should feel a slight tightening beneath your fingers and your stomach should stay flat. At the same time, think of gently drawing your navel in towards your spine until you feel the muscles tightening beneath your fingers. You should still be able to breath normally and have a conversation when these muscles are contracted correctly. Once you have mastered contracting these muscles, you can begin to practice in standing and seated positions until it becomes second nature.
- Additional nutrients are required for synthesis of new tissue and increased energy expenditure, but it’s important to keep in mind that physical activity generally declines during pregnancy.
- 1st trimester: no additional kilojoules required
- 2nd trimester: +1400kjs/day (335 cals/day)
- 3rd trimester: +1900kjs/day (455 cals/day)
Vitamins and minerals
Vitamin B12: extra B12 is required to accommodate the rapid cell division
Folate: adequate supply is necessary for rapid growth and the foetal demand is high compared to maternal stores. Protects against neural tube defects. The neural tube closes 27 days after fertilisation, therefore it’s imperative to take a supplement form of 5mg of folate/day one month prior to conception and continue to take until the end of the first trimester.
Iron: the foetus efficiently extracts iron from the maternal stores and accumulates the most iron in the last trimester. Iron carries oxygen through the blood, including oxygen to the foetus, so adequate maternal stores are essential.
Iodine: low maternal iodine has emerged as a major public health concern in Australia and NZ and can have a serious impact on neurological and cognitive development in the foetus.
Calcium: while the foetus does increase the demand, there are maternal adjustments in metabolism to compensate for this, so additional intake is not imperative.
Omega 3 fats are composed of the 2 active components – EPA & DHA. DHA is essential for the baby’s brain and eye development.
- Preconception – 200mg/a day
- 1st/2nd/3rd – 200-300mg/a day
Best Sources – Fish oil supplements, Flaxseed oil, Fish (keeping tuna, salmon intake to a minimum due to high Mercury levels), walnuts
Alcohol consumption: pregnancy and alcohol do not mix. Alcohol consumption during pregnancy causes damage in two ways:
- Alcohol crosses the placenta, foetal blood alcohol levels rise until it reaches an equilibrium with maternal blood alcohol. Levels are obviously toxic for the foetus.
- Poor maternal nutrition
Infants may weigh less than infants born to women who abstain from alcohol during pregnancy.
Caffeine: moderate intake through pregnancy (300mg/day). This recommendation has been lowered to 200mg/day in the UK due to a weak association between miscarriage and caffeine.
Foods to avoid
Raw or undercooked foods -
- Processed (deli) meats – Ham, salami, luncheon, chicken meat etc.
- Any raw meat raw chicken or other poultry, beef, pork etc.
- Cold chicken or turkey, eg: used in sandwich bars
- Pâte or meat spreads
- Raw seafood (sashimi)
- Ready-to-eat, chilled prawns
- Soft and semi-soft cheese, eg brie, camembert, ricotta, fetta, blue, etc.
- Ice-cream soft serve
- Unpasteurised (raw) diary
- Raw egg in food eg: home-made mayonnaise, chocolate mousse, aioli
Healthy pregnant women are more likely than other healthy adults to get listeria and are more likely to become dangerously ill from it. This can harm the unborn baby as it carries across the placenta.
Lactation: the role of maternal nutrition
Maintenance of milk secretion
- Lactation begins at birth with the removal of the placental oestrogen and progesterone – enables prolactin to promote milk secretion
- Ducts don’t develop fully until onset of pregnancy. Breast tissue increases 2-3 times in pregnancy
- Suckling – stimulates hypothalamus – initiates release of oxytocin (causes release of milk from storage) and prolactin (stimulate milk production) from the pituitary gland – milk supply to infant.
- Milk increases with infants demand – no suckling/stimulus = reduced milk supply
- Synthesis most active during suckling – continues at a lower rate between times
- Fat synthesis: from maternal plasma, carbohydrates or fatty acids
- Protein synthesis: specific milk proteins (not maternal proteins), synthesised in mammary glands
Factors affecting milk composition
- Stage of lactation day to day
- From one breast to the other
- Over the duration of feeding (fore-milk and hind-milk)
- Between women (maternal diet/nutritional status)
Stage of lactation
- Colostrums secreted during the first few days after birth:
Higher in proteins (4-5%) – immune and anti-infective factors
Lower in sugar, fat, energy
- Stage of a feed: initially low fat – 4 x increase by the end of the feed
- Time of the day: greater volume early morning, lower nutrient density
Energy from breast milk
- Minimal change across well-nourished women
- Doesn’t diminish unless under-nutrition is severe
Composition of breast milk lipids (fats)
- Fat in breast milk increases from beginning of feed to end
- Fat provides 50-60% energy
- Fatty acid profile reflects maternal diet and what is stored in adipose tissue
- Fat is in small emulsified globules which are easy to absorb & digestion assisted by lipases in milk
Composition of breast milk protein
- Not greatly influenced by maternal diet
- Amino acid composition differs from cows milk:
Lower in some amino acids: methionine, phenylalanine, tyrosine
Higher in cystine and taurine
Composition of breast milk carbohydrates
- Lactose content is largely independent of the maternal diet
- Vitamins: concentration of water soluble vitamins reflect dietary intake of the mother. Long term effects of high vs low intakes are apparent
Composition of breast milk minerals
- Vary little with maternal diet
- Low levels in human milk reflect bioavailability rather than deficiency
Eg: iron is present in very small amounts but is well absorbed (50%). This is one of the primary differences between cows milk and breast milk
General composition of breast milk
- There are more than 20 enzymes in breast milk to assist in digestion
- Many hormones are present in breast milk, including pituitary and thyroid hormones and steroids) and growth factors
- Healthy infant ingests an average of 750-800mls/day
Factors that influence milk volume
- Nursing frequency
- Birth weight
- Gestational age (premature – less suckling capacity)
- Cigarettes – inhibit prolactin
- Alcohol – inhibits oxytocins (high levels of consumption)
- Oral contraceptives – progesterone inhibits lactation (mini pill)
- Anecdotal: intense activity may alter the flavour of the milk (Lactic acid) and decrease infant intake
- Regular exercise is recommended for lactating women
Nutritional demands of lactation
Dependent upon composition and volume of milk…
- Energy requirements: lactating women require approx 3000kjs (718 cals) to meet the demands of milk production (based on the average synthesis of 850mls/day), but this varies considerably between women.
- It is not recommended that women consume these extra calories to accommodate this demand. Most women will lay down 2-4 kilograms of body fat during pregnancy for this purpose. Women will also generally have a reduction in activity immediately post-partum, which means they are burning less energy.
- Lactating women who are weight-stable: 2000-2100kjs/day
- A loss of 2kg/month is not associated with adverse growth outcomes of the infant
- +17gm/day, or 0.28gm/kg of body weight (RDI = 1.1g/kg)
- Vitamin A (+400 RE/day)
- Thiamine (+ 0.3mg/day)
- Riboflavin (+ 0.5mg/day)
- Niacin (+ 2.4mg/day)
- Vitamin B6 (+ 0.6mg/day)
- Vitamin B12 (+ 0.4mg/day)
- Iron (decrease to 9mg/day) ** once menstruation recommences, return to RDI adult women
- Calcium – no change (1000mg/day)
- Zinc – (+4mg/day)
Other factors which may influence breast milk
- Caffeine: can overstimulate infant (>6-8 cups/day)
- Allergy: breast milk is protective but some suggestion allergens be omitted from the maternal diet
Advantages of breast feeding
Optimum nutrition with low excretion for waste, reduced risk of infection and allergy, optimal weight/growth
Involution of the uterus, decrease postpartum haemorrhage, suppressed ovulation, ease of feeding