The influence of physical activity on pregnancy, labour, a foetus and a newborn

Physical activity during pregnancy and post childbirth brings the following benefits to mother and foetus health:
reduces the risk of preeclampsia, gestational hypertension, and gestational diabetes,
reduces the risk of excessive weight gain during pregnancy and complications during labour,
reduces a risk of post-natal depression and a risk of complications in neonates,
no negative influence on the birth weight and no increased risk of stillbirth.
When there are no contraindications, it is recommended to all women during pregnancy and after childbirth to:
undertake regular physical activity throughout their pregnancy and after labour,
perform at least 150 minutes of aerobic physical activity of moderate intensity during the week, to achieve health benefits,
used various aerobic and muscle strengthening exercises. Adding some stretching may also be advantageous.
Women who habitually intensively practices some aerobic activity or were physically active, can continue that activity during pregnancy and puerperium.

ANY PHYSICAL ACTIVITY IS BETTER THAN DOING NOTHING!

Women who are pregnant or post childbirth, should start with physical activity of low intensity, and gradually increase its frequency, intensity and duration with time.
A training of pelvic floor muscles can be performed every day to reduce the risk of urinary incontinence; however, after seeing a urogynaecological physiotherapist, who will examine the condition of the pelvic floor and decide whether a given woman requires strengthening or relaxing exercises.
Additional safety measures that need to be considered for pregnant women undertaking physical activity include:
• avoiding physical activity during very hot weather, especially high humidity,
• hydration, by drinking water before, during and after physical activity,
avoid physical activities associated with physical contact: posing a high risk of falling or which can restrict oxygen supply, like activities at high altitudes.
Four types of exercises that should be avoided during pregnancy due to a very high risk to a baby, a mother or both:
1. Contact sports (e.g., hockey, box, football, rugby, or basketball).
2. Activities associated with a high risk of falling down (e.g., downhill and water skiing, surfing, riding on a dirt bike, gymnastics and horse riding). 3. Diving (due to foetal pulmonary circulation incapacity).
4. Activities performed at high temperatures (e.g., hot yoga, hot pilates), but also other activities performed in high temperatures, which may lead to overheating. 
Other trainings, though they are not contraindicated, may be associated with a higher risk during pregnancy, but everything should be considered on a case-by-case basis. Activities and exercises that exert unnecessary pressure on the anterior abdominal wall, so they contribute to the increased abdominal separation, cause pain or discomfort within the pelvis, cause urine leakage should not be continued.
NOTE: After the first trimester, avoid activities in a lying position (*aortic-caval syndrome/inferior vena cava syndrome: when a woman is lying on her back, the uterus can press on the inferior vena cava and the aorta. Frequently, the pregnant woman hears a recommendation “lie on your left side”, but it does not mean that she cannot lie on her right side or her back. If you experience dizziness, blood pressure drop, strong movements of your baby or paleness in any of these position, simply change your position.
• After childbirth, return to physical activity gradually, consulting your doctor in the case of caesarean section.
Additionally, the following is recommended:
Women who are pregnant or post childbirth should limit the time spent in a sitting position. Introducing physical activity of any (including light) intensity, instead of sitting, results in health benefits.

Recommendations according to studies: Physical Activity and Exercise During Pregnancy and the Postpartum Perio

Women following a healthy lifestyle who get pregnant should be encouraged to maintain healthy habits. Women who do not lead a healthy lifestyle, should be encouraged to healthier habits before and during pregnancy.
Lack of physical activity and excessive weigh gain during pregnancy were recognised as risk factors for mother’s obesity and associated pregnancy complications, including gestational diabetes.
In the case of no complications, or obstetric or medical contraindications, physical activity during pregnancy is safe and desirable, and pregnant women should be encouraged to continue or initiate safe physical activity.
source: (https://bjsm.bmj.com/content/52/21/1339 )

Examples of exercises that were extensively studied during pregnancy and proved to be safe and advantageous:

walks,
cycling on a stationary bike,
aerobic exercises,
dancing,
resistance exercises (e.g., using weights, bands)
stretching exercises
aerobic in water.

Anatomical and physiological aspects of exercises during pregnancy

Pregnancy causes anatomical and physiological changes that should be taken into account when selecting exercises.
The most noticeable changes during pregnancy include the increase in body weight and shift in the centre of gravity, resulting in an increase in lumbar lordosis. In consequence, over 60% of all pregnant women suffers lumbar and sacral pain.
Strengthening of abdominal and back muscles can minimise this risk.
Continuing with exercises in a lying position after the 20th gestational week may result in reduced venous return due to the pressure by the pregnant uterus on the aorta leading to hypotension, and this haemodynamic change should be considered when recommending modification of exercises during pregnancy.

How physical activity influences the foetus:

The majority of studies on the foetal reaction to mother’s exercises focused on changes in the foetal heart function and birth weight. The studies showed a minimum to moderate increase in the foetal heart rate by 10–30 beats per minute versus the baseline value.
It was found that differences in birth weight were minimal or none.
Women who continued to exercise intensively in the third pregnancy trimester, more frequently gave birth to children weighing 200–400 g less than comparable control groups, though no risk of restricted foetal growth was found.
Benefits continued:
The reduced risk of birth by caesarean section,
Physical activity as an important factor in prevention of depressive disorders in women during the postpartum period.
A better self-assessment of the overall physical fitness and cardiorespiratory function, and this is associated with less pain, e.g., in the lumbar spine.
A reduced risk of hypertension,
No risk of premature birth.

General recommendations:

Rules for exercises for pregnant women do not differ from those for the general population; however, it should be remembered to introduce modifications in some exercises due to anatomical and physiological changes.
An appropriate interview and diagnostics should be performed before starting exercises, to make sure that there are no contraindications to undertaking or continuing physical activity.
Introducing exercises of moderate intensity.
Women should be advised to hydrate well, avoid long periods of lying flat on their back and stop exercises when any of the following symptoms develop:

NOTE! You should stop your training when any of the following problems develop (AND CONSULT A DOCTOR):

bleeding from your vagina,
abdominal pain,
regular painful contractions,
amniotic fluid leaking,
dyspnoea before starting exercises.
dizziness,
headaches,
chest pain,
weakening of muscles that contributes to loss of balance,
pain or swelling of lower legs.

Restricted activity:

No reliable evidence is available supporting the recommendation to lie in bed during pregnancy to prevent premature birth, and this should not be a routine recommendation.
Women recommended prolonged rest or restricted physical activity are at risk of developing venous thromboembolism or bone demineralisation.
No studies document an improvement of results in women at risk of premature birth who restricted their activity, and this includes lying in bed. However, there are reports confirming negative consequences to the mother and the family of limiting the routine activity, including negative psychosocial consequences. The restricted activity should not be routinely recommended to reduce the number of premature births. There is also no evidence available that lying in bed reduces a risk of developing preeclampsia and its complications.

Contraindications to physical exercises during pregnancy

Women suffering with the following disorders or complications should not exercise during pregnancy:
certain heart and lung diseases,
an incompetent cervix,
a twin (and any other multiple) pregnancy with risk factors of premature birth,
placenta previa after the 26th pregnancy week,
preeclampsia or uncontrolled gestational hypertension*
severe anaemia,
uncontrolled thymus disease,
foetal growth restriction.
Relative contraindications include:
recurring losses of a pregnancy,
gestational hypertension,
spontaneous premature birth in the interview,
mild/moderately severe cardiovascular or respiratory disease,
symptomatic ischaemia,
malnutrition/an eating disorder
twin pregnancy after 28th week,
other important disorders.

The training intensity in terms of the pulse range:

Physical activity of moderate intensity, at a level of 40–59% of the heart rate reserve (HRR) or of high intensity at a level of 60–80% HRR, is recommended.
Another measurement of activity intensity includes “speech test” - a woman is comfortable while exercising when she is able to maintain conversation during that time. If it is not possible, that intensity should be reduced. 
Source: 2019 Canadian guideline for physical activity throughout pregnancy
Based on World Health Organization (WHO) guidelines:
(https://www.who.int/publications/i/item/9789240015128 )

Lessons in HiMommy app

Before starting your training make sure that your doctor gives their consent to it and you have no medical contraindications to undertake physical activity. 
If you feel able to exercise and are at an advanced level, you can perform all trainings throughout the pregnancy (the only exception are series performed when lying on your back). If you are just starting, do trainings with bands and dumbbells only until the end of the second trimester, in the third, focus on exercises with the weight of your own body and on relaxing trainings. Warming up can be performed as a separate starting lesson, e.g., to begin your day.
Before you start your exercises, carefully read a description of a lesson, make sure to warm up, if necessary, and check whether a given training is suitable for you at a given stage of your pregnancy. 
If you are a beginner, start with warming up, stretching, and exercises with the weight of your own body, to learn the exercise technique first. 
Warming up:
During next 10 minutes, you will prepare your body for the main part of the training, which you can select from those available in the application.
The aim of this part is to increase your body temperature and to prepare your joints for further exercises. You will focus on increasing mobility, to safely move to the strengthening part.
Training 1 - Stretching
This training can be performed without warming up.
Required equipment: yoga blocks/books and a yoga strap/belt/shawl
The aim of this lesson is to relax the entire body. Using simple accessories available at home, you can perform a relaxing training. It is a perfect solution to start your morning or to end a difficult day, as well as when you feel discomfort or pain in the lower back. Focus on your breath, for the excessive tension to leave your body.
Training 2 - with your own body weight
This training can be performed without warming up.
Required equipment: a chair
The aim of this lesson is to introduce various motion patterns and changes in the position that will work perfectly during pregnancy, but also after birth. As your pregnancy progresses, the growing belly changes your posture, so during this lesson you will learn how to perform exercises correctly. This would have a positive effect on maintaining the correct posture and taking pressure off your back.
Training 3 - with your own body weight
Before this training, perform warming up, or perform it as a continuation of Training No. 2.
Required equipment: none
The aim of this lesson is to strengthen your body using simple exercises. Pay attention to the technique and try to perform movements as precisely as possible. Various forms of exercises are presented during the lesson, so you can adjust the training intensity and difficulty to your strength at a given time.
Progression: in successive weeks of training, instead of performing three series of exercises shown in the video, you can pause the lesson and perform one or two additional series of your favourite exercises.
Training 4 - with mini bands
Warm up before this training. Before you start your training, place the band of higher resistance under your knees. 
Required equipment: Two training mini bands, one of lower and one of higher resistance, or both of the same resistance.
Load selection: the bands usually differ in their resistance. If you have bands of different resistance, use the lighter one for exercises for your hands, and the stronger one for the lower part of your body.
The aim of this lesson is to further strengthen your body using mini bands. Pay attention to the technique and try to perform movements as precisely as possible. If you feel tired, perform a shorter series, or take a longer break than the one proposed during the training.
Progression: in successive weeks of training, instead of performing series of exercises shown in the video, you can pause the lesson and perform one or two additional series of your favourite exercises.
NOTE! If you know that lying on your back is not good for you and you feel unwell or dizzy, do not exercise in this position!
Training 5 - with dumbbells/kettlebells
Warm up before this training. This lesson is in fact a progression of previous trainings, but using additional weights. 
Required equipment: 2 dumbbells/kettlebells/weight plates - from 2 kg up to even 4–6 kg (bottles with water can be used instead), a chair, and a mat for the last series.
Selection of load: If you have no experience in the strength training and are at the beginning of your adventure with weights, start with lighter dumbbells, e.g., of 2 kg. If you are experienced and trained before your pregnancy, and additionally, your technique is perfect, there is no contraindications to use greater weights, even 4–6 (up to 8) kg.
The aim of this lesson is to strengthen your body using additional weights. Pay attention to the technique and try to perform movements as precisely as possible. This training is a progression of all previous ones. It is based on movements that you have already learnt. If you feel tired or feel that your technique is not very good, perform less repetitions or rest longer.
Progression: in successive weeks of training, instead of performing two series of exercises shown in the video, you can pause the lesson and perform one or two additional series of your favourite exercises.
NOTE! You can perform a series of exercises lying on your back longer than until the end of the first trimester. However, if lying on your back is not good for you and you feel unwell or dizzy, do not exercise in this position regardless of the pregnancy stage.
Cool down
This part focuses on calming down at the end of the training. You will work on relaxing and stretching individual parts of your body that participated in the training.