What is the Role of BMI During Pregnancy?

Pregnancy is one of the most desired phases of every woman’s life. It is really a wonderful feeling for the ladies to carry a life inside her womb for almost nine months and nurture the child inside her. They can feel the baby inside them as the fetus starts to grow and as time passes they get emotionally attached to their child even when he is not present in this physical world. That’s the reason most of the ladies forget all the hardships and the physical pain when they see their child in their laps for the first time and have tears of joy in their eyes and gracefully embrace the new life as a mother. 

As we know there are many complications and health issues associated with pregnancies. You have to take care of yourself for almost every month during the period. You have to eat a proper diet, refrain from some of the delicacies during these months as there is another life inside you. So you need to take care of health during the pregnancy period. Therefore Body Mass Index also plays an important factor during the pregnancy. Your body should have proper weight and you must not become obese as it might lead to various complication when you are going for delivery of a child.

What is an Ideal Weight During Pregnancy According to BMI Index?

The normal pregnancy period for ladies is 9 months. So the pregnancy period of a women can be divided into 3 months each which are as follows:

MonthsPregnency Period
1-3 monthsFirst Trimester
4-6 monthsSecond Trimester
7-9 monthsThird trimester

If you have less than normal weight when you deliver a baby, your baby will be born small and they may have problems during breastfeeding and are also at great risk of illness. If by chance you gain more weight during pregnancy, your baby can be large in size when born and you may have to go through cesarean delivery. It can also lead the child to be obese and after the pregnancy period you will also gain weight which may led to obesity. You can see the below table to see how much weight gain is recommended after you get pregnant according to BMI Index.

Ideal Weight Gain During Pregnancy

BMI Index Before PregnancyIdeal Gain Weight
BMI < 18.512.5 kg–18 kg
BMI between 18.5 – 24.511.5 kg–16 kg
BMI between 25.0 – 29.97 kg–11.5 kg
BMI >=305 kg–9 kg

If a lady is expecting twins, it becomes more important to gain the right amount of weight. It is most often the case that twins are born early before the due date, therefore they need to be on the heavier side when they get born into this real world. Therefore you need to maintain an ideal weight and according to BMI below is the table depicting the ideal weight when a woman is carrying the twins in her body during pregnancy:

Ideal Weight Gain During Pregnancy For Twins

BMI Index Before PregnancyIdeal Gain Weight
BMI < 18.519 kg–27 kg
BMI between 18.5 – 24.517 kg–25 kg
BMI between 25.0 – 29.914 kg–23 kg
BMI >=3011 kg–19 kg
Now let’s go through the different phases of a pregnant woman and see what is the right amount of weight during the three trimester.

BMI During Pregnancy First Trimester

The first trimester is the most delicate phase of the pregnancy when the foetus is developed inside the the womb of a lady. During this period, women don’t need to gain more weight. If you have already maintained a good weight according to BMI at the start of your pregnancy you will have to gain only 1 to 4 pounds which is equivalent to 0.5 – 0.8 kg. It can be gained by eating a healthy diet and you need not take any extra calories during the first trimester.

If you suffer from nausea, you can include snacks in your diet regularly which can lead to weight gain which is above normal. You can have biscuits and bread which have whole grains included which are the source for many nutrients and will provide you with long-lasting energy. You can have fruits instead of chocolates and ice cream if you are having cravings for sugar.

BMI During Pregnancy Second Trimester

The second trimester starts from the 4th month of pregnancy and will remain till the 6th month. In these months you will gain weight rapidly. It is because the body adds a lot of water. You will feel thirsty even when you feel like you already have lots of water in your stomach. Your belly will swell up and also have an extra fluid known as amniotic fluids which will add to extra weight. Your uterus will also grow rapidly. Also, there is an increase in the amount of blood volume which is around 50%. Therefore gaining a lot of weight in the second trimester is just a normal case.

The rate of weight gain in second trimester is dependent on your BMI before you become pregnant. Therefore weight gain during second trimester according to the BMI is:

Weight Gain During Pregnancy Second Trimester According to BMI Before Pregnancy

BMIWeight Gain Second Trimester
BMI <18.5kg/m500g/week
BMI 18.5 to 24.9kg/m400g/week
BMI above 25kg/mLess than 300g/week

BMI During Pregnancy Third Trimester

The third trimester is the most important phase of pregnancy. Most of the women during this phase gain weight rapidly. It is because of the foetus which gains a significant amount of weight in this period. The average weight gain is 0.2-0.5 kg and around 4-6 inches during third trimester. The body will also gain weight from the following:

Amniotic Fluid, The Placenta, The breast tissues, Increased supply of blood, A larger uterus, storage of fat for delivery and breastfeeding.

During the third trimester you may also see that your weight is getting steady during ninth month. It is important to gain gradual weight during the third trimester as the baby who is in the womb of the lady requires sufficient nutrients and calories to grow properly. The amount of weight gain during third trimester should be according to your BMI as shown in the table below:

Weight Gain During Pregnancy Third Trimester According to BMI Before Pregnancy

BMIWeight Gain Third Trimester
BMI <18.5kg/m400g/week
BMI 18.5 to 24.9kg/m300g/week
BMI above 25kg/mLess than 200g/week

What are the risks associated with higher BMI during pregnancy?

As we already know, the Body Mass Index is a relation between persons height and weight. It is used to measure whether you are underweight , overweigt or obese. When you get pregnant you should calculate your BMI and as per the normal calculations these are the figures for various BMI :

BMIHealth Risk
BMI < 18.5Underweight
BMI b/w 18.5 – 25Healthy 
BMI > 25Overweight
BMI > 30Obese
BMI > 40More than Obese

So we will see below the health problem associated with the higher BMI for the pregnant women:

Preeclampsia – This is a health disorder associated with high blood pressure. It can occur during pregnancy and also after pregnancy which can affect your entire body. You may suffer from kidney and liver failure. Moreover you can also suffer with eclampsia which leads to seizures. If you get this disorder it might be needed to deliver the baby early.

Gestational Diabetes – You may need to have cesarean delivery if you suffer from this condition. Your child may also suffer during later stages of his life from diabetes.

Sleep Apnea – A condition in which you might stop breathing for short periods of time. If this happens during pregnancy, you can suffer from fatigue and it will result in high blood pressure which can lead to heart and lung disorders.

How to maintain a healthy weight during pregnancy in accordance with BMI?

Pregnant women need to eat healthy to gain significant weight according to trimesters. You will have to take care of calories intake during your first, second and third trimester. In the first trimester you need no additional calories per day whereas in second trimester you need to have around 340 calories extra and in third you will need around 450 additional calories to maintain a proper weight according to your Body MAss Index. The calories intake can be summarised in the following table:

Calories Intake for healthy Weight Gain During Pregnancy

First No extra calories
Second340 calories per day
Third450 calories per day

There are other things to follow to gain significant weight during pregnancy which are described below.

Eat Healthy: During pregnancy you will require lots of proteins, carbohydrates and fats which is required for the energy. You can have nuts, fish, olive oil  to gain unsaturated fats. For the carbohydrates you need lentils, low fat milk products, whole grains and fruits.

Eat in Small Portions: When you are in the last months of your pregnancy period, your stomach has less area to expand, therefore it might be difficult to digest food in one sitting. Therefore try to eat in small portions.

Exercise regularly: If you exercise regularly for sometime, you may avoid risks of complications of the pregnancy. Also it will help in reducing back pain during pregnancy, and reduce constipation. You should go for aerobic exercise which include walking, cycling, yoga and swimming.

Increase intake of Folic Acid: Before you are planning pregnancy, increase your intake of folic acid 2-3 months prior to pregnancy. intake of folic acids reduces the risk of babies born with birth defects. Folic Acid is a basic Vitamin B so avoid the medicines having multivitamin.

Iron intake: Increase the intake of products which include iron. Iron is necessary for the increased supply of blood to foetus and the body of pregnant women. You need to to have 16-20 mg of iron intake daily during your pregnancy period. Foods which are rich in iron includes red meat, green vegetables, cereals, pulses and bread.

Avoid Sugar and Solid Fats: To avoid this you need to say no to cold drinks, meats, desserts and fried foods.

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