How Many Months Are 20 Weeks? Get Ready To Be Shocked

You missed your periods. It is now somehow quite apparent that you are pregnant. You start noticing some increase in weight, nausea in the morning, change of moods and sooner or later, you will visit your doctor and start hearing the words weeks, trimesters and months and that’s when confusions will chip in, leave alone that, you will start asking yourself how many months are 20 weeks? Well, keep reading, and you will find your answer.

Pregnancy periods according to most gynecologists take approximately 40 weeks, your 20 weeks will be half this period, and since each month has 4 weeks, you are in your 5th month. There you have it. You are 5 months pregnant.

The above case, however, might be a little bit complicated if it is looked at in deeper details. The simple answer to the above question might be 4 or 5 months. The correct answer will depend on whether it is fetal age or gestational age. To find the answer to how many months are 20 weeks, you need to dive a little deeper into knowing pregnancy duration measurement methods.

How Is Pregnancy Lengths Assigned?

Assigning of pregnancy lengths is one of the hardest things not for you but also for your obstetrician. This is because there are factors that come into play like when exactly was your last period?

If you will be able to clearly state your last menstrual period you will be on an easy road to knowing your estimated due date (EDD).Pregnancy lengths are generally given in the form of days, weeks, months and trimesters.

Pregnancy Length In Terms Of Days

Pregnancy in general starts from the day conception of your child occurs to the day of birth. This is about 266 days (fetal age). Conception is the time at which a male sperm fertilised your female ovum. This normally occurs 14 to 16 days after the first day of your last menstrual period.

 Conception varies from one woman to another; it also depends on the number of days the sperm took after copulation, to fertilise your female egg. To avoid confusion and inaccuracies, pregnancy experts therefore normally count pregnancy days from the first day of the last menstrual period (gestational age) which will add up to 280 days to delivery.

Pregnancy Length In Terms Of Weeks

Weeks is one of the key conventional measurement units for pregnancy. Experts approximate that pregnancy will take 40 weeks after the first day of your last menstrual period (gestational age) or 38 weeks from the first day of conception(fetal age). This therefore means that a 20-week pregnancy is 140 days old (gestational) or 126 days old (fetal age).

Confusion, however, might occur when you are on your 22nd week, and you realise your doctor is referring to your baby as a 20 weeks old. Conception occurs 14 days after your last menstrual period, well that is why your baby is 20 weeks old, and you are 22 weeks pregnant. This will get simpler when you learn more about converting your weeks to months.

Pregnancy Lengths In Terms Of Months

Many people believe that pregnancy lasts nine months but according to the Gregorian calendar, months of the year have between 28 – 31 days. Since normal pregnancy takes 40 weeks, you might realise that pregnancy takes a little bit longer than 9 months when calculating the number of months using the normal calendar days.

It is strongly advised that to get estimated birth dates using calendar dates you will need to add up to 7 days to your ninth month date. For example, if the first day of your last menstrual period was on January 1st, first add up the 7 days, then add up your 9 calendar months, your estimated due date will be on October 8th.

To convert your weeks to months, gynecologists estimate that every month has 4 weeks. Therefore your pregnancy of 40 weeks will be 10 months; now you are confidently sure that a 20-week pregnancy means you are in your 5th month.

Getting exact due dates or birth dates is so hectic that it prompted organisational bodies like world health organisations to adopt a lunar system of determining pregnancy lengths. It suggests that a lunar month has 28 days. A 280 days pregnancy will, therefore, be 10 months.

However, a true lunar month has 29 days, 12 and 3 quarter hours. A 280 days pregnancy, therefore, is 9 and a half lunar months. This system was found to be confusing hence the reason it was globally disputed.

Pregnancy In Terms Of Trimesters

The trimester is a Latin origin word trimestris. Tri means three and mestris means months, trimester therefore means a set of three consecutive months. Trimester in pregnancy is a very important term for describing fetal development from fertilisation to birth. It is also helpful in determining your pregnancy length.

The first trimester is commonly defined from the first day of your last menstrual period to the end of the 13th week. The second trimester is from your 14th week to 26th week and the third trimester is from the 27th week to 40th week.

It is very important to note that; it is the 40th week, not 39th week because one extra week is added as an estimate before delivery occurs.

Most pregnancy experts will prefer using weeks than months and trimesters as a way of determining the lengths of pregnancies. However, it is important to note that trimesters help in monitoring the development of your baby for instance;

Indicate the period of fertilisation, embryo development and also placental growth. This is where you will experience a lot of symptoms as you adjust to hormonal changes in the body. This is the period at which miscarriages might occur due to the failure of corpus luteum to sustain the pregnancy.

You will experience less and less early pregnancy symptoms with time. The embryo develops human features like legs, fingers, arms and its body parts like the kidney will start working. At this point, it will be called a fetus. At this stage, you can tell the sex of your baby. The fetus will not, however, survive if delivered.

During this stage, the fetus is fully developed and can respond to stimuli like light, sound and touch. If born prematurely it will survive.

Wrapping Up: When Will Be Your Due Date? After 9 Or 10 Months?

Gynecologists will most likely use the gestational age in determining your pregnancy. This means your pregnancy will be determined from the first day of your last menstrual period; it will therefore last for 280 days which is approximately 9 and half months. That’s the furthest they can go in guessing your due date.

The good news is that your estimated due date will lie in between these two months. Estimated due date is nothing but just estimates that should never come between you and having a good diet, exercising and living a good lifestyle that will ensure that you have a safe and successful delivery. 

Less than a tenth of all deliveries have their due dates accurately determined, you will be the luckiest mum if you will be in this category, and chances are you will be among the majority. It is therefore very crucial to remain calm and live through your expectancy.

Kristi Cathey

Hi everyone! My name is Kristi Cathey and I’m glad you found your way to my blog. I am a mother of 3 beautiful angels. This blog was created in order to share my personal experiences in baby care and general health care for pregnant women. If you'd like to get in touch with me, please contact me by sending me an email via Welcome to

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