The Fifth Month of Pregnancy Week by Week

By BSc, MSc (embryologist).
Last Update: 01/11/2019

The fifth month of pregnancy encompasses from week 17 to 20 and is part of the second trimester of pregnancy. The most obvious symptoms to expect are, on the one hand, the increased size of the breasts and the belly, as well as the first baby movements.

The fifth month of pregnancy is the halfway point of pregnancy. In fact, it is the moment when the pregnant woman starts enjoying it, since the miscarriage rate decreases and the symptoms are not so uncomfortable yet.

Changes in the mother

The changes a woman who is 5 months pregnant may experience are actually quite similar to the previous month. Nonetheless, these symptoms increase during this period without becoming particularly annoying.

What to expect

It is likely that you experience a weight gain of between 2.5 to 5 kg in this stage of pregnancy and you may feel that your legs and ankles are swollen. At the same time, this weight gain can make you feel more tired and bloated. This set of symptoms can get worse due to intra-abdominal pressure, causing you to breath differently and aggravating the feeling of fatigue.

The increase in your breasts size is due to hormones preparing your mammary glands to start producing milk. Areolas become darker and the veins become more noticeable to the naked eye. It is likely that, during this month, you have to use nursing bras or, at least, a larger size.

Despite fetal weight is not greater than 300 g at this stage of pregnancy, its growth may start affecting your organism. You might notice certain symptoms in your backbone that cause you to change your daily positions. In fact, you might feel clumsier when walking due to the size of your baby.

It is normal to feel an increased sensation of thirst. For this reason, we recommend that you increase your daily intake of liquids as well as avoid holding your urine. Both practices, at the same time, are highly beneficial for preventing Urinary Tract Infections (UTIs), which can cause complications during pregnancy.

Other common symptoms

The following are more common symptoms you are likely to feel during your fifth month of pregnancy:

Sciatic pain
It is the inflammation of the sciatic nerve, located in the lower back, which can extent to one foot. Hormone relaxin, responsible for the distention of the ligaments to favor the expansion of the uterus, can be the cause of this annoying symptom.
Cramping
Involuntary muscle contractions that typically appear in the legs due to your uterus expanding. Since this can cause pressure in the nerves and blood vessels of the lower extremities, it causes annoying cramps.
Constipation
It is one of the most common complications of pregnancy. As a consequence of hormonal changes during pregnancy, bower movements decrease.
Hemorrhoids
A circulatory disorder caused by a dilation in the rectal veins. It is associated with constipation to a large extent.
Heartburn
Caused by reflux of stomach acids to the esophagus. Since progesterone causes a delayed stomach emptying and the expansion of the uterus exerts pressure on the lining of the stomach, the heartburn sensation increases.
Palpitations and tachycardia
An increased blood flow, necessary to support the growing baby, forces the heart to support a heavier workload. For this reason, its functions can be a bit altered.

Changes in the fetus

By the end of this month, the fetus will have acquired an average length of 25 cm from head to toes, and a weight of about 300 g. The face has not acquired a rounded shape yet and the size of the eyes is a very prominent one. The skin is not so transparent as in previous months.

During the fifth month of pregnancy, the fetal internal organs go through a major development process. For instance, the circulatory system is now considerably developed, the auricles and the ventricles of the heart are delimited (the four chambers that form the heart), and it is able to beat vigorously now.

At this stage of pregnancy, the size of the fetus is similar to a pear, and it can be differently positioned, since he has still enough space to move freely. It is not uncommon that, with each prenatal visit, fetal position is different: lying on his side, breech position, etc. From this moment on, you will start noticing his movements more intensely.

Week 17

One of the most important changes in the baby during this month of pregnancy is the appearance of the vernix caseosa, a cheesy-like substance that covers the body of the unborn baby. The function of this fatty layer is to protect the skin of the baby from the irritation caused by amniotic fluid and dehydration. Normally, it is present to the momento of birth, although not all babies are covered with it at birth.

The placenta increases its size and acquires millions of blood vessels that transport components and oxygen from the mother’s body to the baby’s.

Week 18

When the woman is 18 weeks pregnant, his length is about 14 cm and the weight is 150 g. Eyes and ears are now in their final position. The baby can yawn, make facial expressions, or even have hiccup, since his digestive system is already working and he can swallow. The vocal chords are fully develop and he could even cry.

Given that the bones of his internal ear and most of his nerve endings of the brain are almost fully formed, he can distinguish the sound of his own heart or the voice of his mother. A number of doctors recommend that you stimulate the fetus with music or just talking to him in order to improve his hearing ability.

Week 19

The baby’s heart is beating unstoppably and its four chambers develop through this month. Simultaneously, the skeleton is developing as well, and bone tissue starts forming out of the soft cartilage.

During this week of pregnancy, the baby sleeps for longer periods, and wakes up with more energy as a result. For this reason, it is likely that you notice a greater number of episodes of fetal movement, as well as moments of total absence of fetal activity.

The measurements of the baby in week 19 of pregnancy are 15 cm long approximately. Finding out your baby’s gender is more common by this time.

Week 20

At this point of his development, the baby’s size and proportions are almost human. He can reach a length of about 15 cm and weight 250 g.

You may notice that your skin is more stretched than before, and the position of your uterus is almost as high as your belly button.

Week 20 marks the beginning of the second trimester of pregnancy. For this reason, from this week on, you should take special care of your diet and the activities you do on your daily routine, since you need a greater amount of minerals and nutrients, especially iron, to make sure that your baby is growing healthily.

Prenatal visits

At this point of pregnancy, you will have to run another fetal ultrasound, particularly the one called second trimester morphology ultrasound. The goal of this test is to:

  • Confirm the date of birth
  • Examine fetal anatomy
  • Detect potential anomalies
  • Control the amount of amniotic fluid
  • Examine fetal activity based on fetal movement
  • Confirm the gender of the baby

Your doctor may suggest that you undergo the triple screen test, also known as triple test or multiple marker screening. This test includes a blood test to determine if there are chances for the baby to have some kind of chromosomal abnormality.

Week 20 of pregnancy is an ideal moment for you to do a HD ultrasound. This test includes a conventional ultrasound scan that is able to provide a clearer picture of the baby.

FAQs from users

I am 6 months pregnant and do not feel my baby move, should I be worried?

By Victoria Moliner BSc, MSc (embryologist).

This stage of pregnancy characterizes for the fact that the baby starts moving vigorously. However, each pregnancy is different and fetal development does not always follow the same pattern. In any case, we suggest that you visit your doctor and tell him or her about these symptoms to see if it is a sign that something is not going as it should.

Can you have an abortion at 5 months of pregnancy?

By Victoria Moliner BSc, MSc (embryologist).

With 5 months of pregnancy, abortion is possible only if the pregnancy is a life-threatening factor for the woman or compromises her health severely. Also, if developmental abnormalities that are incompatible with life are detected in the fetus. A pregnancy can be terminated for these reasons up until week 22.

For a voluntary termination of pregnancy to be free of risks can be performed only until week 14.

What are the potential pregnancy complications in the second trimester?

By Victoria Moliner BSc, MSc (embryologist).

Potential risks or complications associated with this trimester of pregnancy are:

  • Gestational diabetes
  • Anemia
  • Urinary tract infections
  • High blood pressure
  • Threatened miscarriage
  • Sudden birth

Is it normal to have contractions at 5 months?

By Victoria Moliner BSc, MSc (embryologist).

Yes. In fact, from the 5th month onwards, you are likely to feel Braxton-Hicks contractions, which help your body to get ready for childbirth. Their intensity increases progressively as the pregnancy progresses and can become more frequent during the final weeks. They are different from birth contraction because they appear at this stage of pregnancy, occur often as an isolated event, and are painless.

Suggested for you

Once week 20 of pregnancy comes to its end, the sixth month of pregnancy begins, a moment when we can consider that fetal development is in an advanced stage. Learn more here: What Happens during Your Sixth Month of Pregnancy?

Also, if you want to get an overall idea of what happens throughout all months of pregnancy, we recommend that you visit this guide: Pregnancy Stages by Month – Fetal Development with Pictures.

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.

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Grupos de trabajo de la Guía de Embarazo y Parto, Guía de Salud Oral, y Guía de Lactancia Materna. Consejería de Sanidad, Dirección General de Salud Pública y Servicio de Salud del Principado de Asturias. Octubre de 2015.

Health Service Excecutive (Feidhmeannacht na Seirbhíse Sláinte) (2010). A guide to your pregnancy month by month. Breastfeeding.ie - Your breastfeeding support network. Order Code: HPM00341

March of Dimes, Pregnancy & Newborn Health Education Center. Exercise during Pregnancy. Retrieved March 11, 2008

National Health Service (NHS) (UK) (2009). The Pregnancy Book. Your complete guide to: A healthy pregnancy, Labour and childbirth, The first weeks with your new baby. Crown copyright 2009. Produced by COI for the Department of Health.

Obstetricia 4ª edición. J. González Merlo. Ed. Masson. Barcelona, 2003

Ramírez García O, Martín Martínez A, García Hernández JA. (2003). Duración del embarazo. Modificaciones de los órganos genitales y de las mamas. Molestias comunes del embarazo normal. Panamericana Ed. Tratado de Ginecología, Obstetricia y Medicina de la Reproducción. Cabero Roura L, Madrid.

The American College of Obstetricians and Gynecologists. (2005). Your Pregnancy and Birth (4th ed.). Washington, DC: Meredith Books.

The American College of Obstetricians and Gynecologists (2011). Frequently Asked Questions (FAQ156). Pregnancy.

The American Dietetic Association. (2008) Position of the American Dietetic Association: Nutrition and Lifestyle for a Healthy Pregnancy Outcome. Journal of the American Dietetic Association. 108:553-561.

U.S. Food and Drug Administration (FDA). Food Safety for Moms-To-Be. Retrieved April 09, 2010

FAQs from users: 'I am 6 months pregnant and do not feel my baby move, should I be worried?', 'Can you have an abortion at 5 months of pregnancy?', 'What are the potential pregnancy complications in the second trimester?' y 'Is it normal to have contractions at 5 months?'.

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Authors and contributors

 Victoria Moliner
Victoria Moliner
BSc, MSc
Embryologist
Degree in Biochemistry and Biomedical Sciences from the University of Valencia (UV). Master's Degree in Biotechnology of Human Assisted Reproduction from the UV and the Valencian Infertility Institute (IVI). Presently, she works as a Research Biologist. More information about Victoria Moliner

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