"Physiologically, there are a lot of good reasons why you might be tired when pregnant," says Obstetrician and Gynaecologist Dr Philip Zinn, at Kingsbury Hospital in Cape Town.
"A baby's prime purpose is to command the resources of its mother, and the mother comes second. It does this by making sure that it gets preference for circulation, preference for oxygen and preference in terms of nutritional requirements."
"Every heartbeat, every enzyme action, every cell that's growing (at a very fast rate) in your baby, comes from your energy," he says.
Blood pressure plays a big role in fatigue when pregnant. "You're not able to adjust your blood pressure as quickly as when you're not pregnant and when you fall pregnant, your blood pressure drops."
Once you get to your second trimester, it goes down to its lowest point, and while it starts to pick up through the pregnancy, it remains, on average, low.
"Low blood pressure is a natural state of pregnancy, and it's a reason for feeling tired. You don't compensate as fast as you would if you weren't pregnant".
"The hormones of pregnancy and the need to shed extra heat cause blood vessels to dilate and remain dilated even when the blood pressure is too low for you".
"This is why when you're lying down, and you stand up too quickly, your blood pressure doesn't equalise fast enough, and you might feel faint and fall over," he says.
Haemoglobin is the iron-containing pigment of the red blood that transports oxygen from your lungs to the rest of your body.
Levels of haemoglobin also drop during pregnancy because your blood is diluted, and the thinner blood circulates more easily through the placenta.
"What's more, the baby has a different kind of haemoglobin which will grab oxygen from the mother even if the mother's levels are low - yet another reason your baby is tiring you out," explains Dr Zinn.
"As a result of the greater oxygen demands, your heart has to work more vigorously during pregnancy, and your reserves are prioritised for your baby. All of this is tiring," he says.
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Not only is your sleep disturbed when you're pregnant because you're uncomfortable (in the third trimester), it's disturbed through pregnancy because of high oestrogen levels that act as a stimulant.
High oestrogen levels make you more sensitive to all stimuli, and deep sleep is a thing of the past.
"Perhaps this is why – once you have your baby – you might wake up to your baby's cries while your partner sleeps all night peacefully long! The point is, you're attuned to sleep lighter and as a result, end up tired in the morning," says Dr Zinn.
When is it at its worst?
According to Dr Zinn, many women feel fine in their first trimester, but there are a lot of physiological changes and increased energy demands.
Those who are used to running around but are also suffering from nausea and painful breasts and with lower blood pressure, feel very tired. Most notably, it's a stark contrast to what they felt before.
"In the second trimester, your blood pressure drops even further, and if you were able to relax in your first trimester, you would feel more tired in your second trimester when your blood pressure is at its lowest (around 16 weeks or so), and you might want to sleep all the time."
"From about the 18/20 week mark, you will most likely feel a renewed energy. And 20 to 28 weeks is a nice time of pregnancy for all sorts of reasons – one of the main reasons is having the reassurance that everything is okay with the baby and the pleasure of feeling the baby move."
The weight of the pregnancy is more manageable at this time.
The anxiety of the first and second trimesters can be quite significant, and there are lots of psychological buoyancy effects that might give you more energy.
"As the third-trimester advances, mechanics will, of course, take over. Everything will start to crack, your centre of gravity shifts, your muscles and ligaments start to take the strain, and you're constantly carrying a baby in front of you", Dr Zinn says, explaining that your body needs more energy to deal with all of these aches and pains.
Other reasons for exhaustion
One of the most common pathological reasons Dr Zinn sees for exhaustion during pregnancy is the common illnesses that everyone else gets.
"When you're pregnant, your immune system is compromised, and you're more vulnerable to coughs and colds. You may also not recover fully from a cold before the next one comes along," he says.
He also stresses that social issues – for example, demands at work, other family members, and the inability to be able to go and lie down when you're tired – can leave you feeling exhausted and take a huge toll on the body.
"Psychological issues such as positive and negative stress (a trip overseas, lots of exercises, illness or not eating properly) can also impact how tired you are."
Stress can and does have a physiological effect on the body and leaving it tired. "Anything that requires the body's additional resources will sap your energy," he says.
Lastly, he believes that society doesn't have much empathy for pregnant women and not only are they expected to carry on at the same pace as before (even though they are functioning for two), but women themselves work till 38 weeks, exercise as before and carry on at the same pace.
All of this is exhausting.
When to worry
Screening tests in early pregnancy will help your doctor determine if you're already at risk. For example, if your haemoglobin levels are already low, you might be predisposed to anaemia.
Secondly, if you are excessively tired, it's worth telling your doctor as you might have thyroid issues that have only cropped up since being pregnant – you might have an underactive thyroid.
Thirdly, heart and lung function have to be considered too. Lungs have a great capacity. Even if their function is poor, they can still cope well with pregnancy. The heart, on the other hand, doesn't have much additional capacity.
If you have an underlying heart problem that you didn't know about, it might manifest for the first time in pregnancy.
And a lot of the symptoms are typical symptoms of pregnancy which is why it may be missed until it becomes serious, explains Dr Zinn.
"Unusual fatigue, shortness of breath, fainting spells, and feeling worse when you're lying down are all signs that something is wrong," he says.
"If you feel that things don't quite click, then you need to let your doctor know right away and get a thorough physical examination".
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Six ways to get your energy back
Put your feet up
This is not an old wives' tale – it's something that you have to do, for at least 15 minutes a day. If you're at work, put your head down on your desk during your lunch hour and sneak a catnap.
If you're at home – now is when it's okay to let your older children watch some TV! Nobody expects you to be a supermom.
Towards the end of your pregnancy, your body will start to take more and more strain.
Yes, this might be your last few weeks alone with your other children before a new baby comes into the picture, but don't let your guilt push you beyond your limits. Reel in granny and grandpa or hire help.
Learn to say no
To social commitments, to the mess in the house, to your boss who expects you to be on your feet for 8 hours a day or work overtime.
This is your body and your baby, and you need to put it first.
When carrying one baby, you need about 300 extra calories every day. You're going to have the odd craving, and in the first trimester, it might be tough getting lots of healthy meals down.
But in general, a healthy diet made up of vegetables, fruits, whole grains, skim milk, and lean meats can give you energy. Drink lots of water.
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In addition to this, you need to cut back on caffeine and make sure you're drinking plenty of water. If you're spending your nights on the loo, try not to drink a few hours before bedtime but rather drink lots during the day.
Exercise, gently, every day.
We don't expect you to train for a marathon, but a short walk can give you more energy – even if you can't pull yourself up off the couch to put your shoes on. Unless your doctor has told you not to exercise, make exercise part of your daily routine (30 minutes max).
If you're running around after a toddler – you'll probably find you've done enough working out for the day. In that case, use your free time to go chill out somewhere by yourself.
And remember to breathe.
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