Month by Month Guide to Prenatal Development of Baby

Learn the prenatal development of baby by the growing months

By Michele
Month by Month Guide to Prenatal Development of Baby

Want to have a baby but finding it difficult to conceive? Getting pregnant but having miscarriages? You’re not alone. Many couples are facing these same problems, but some knowledge about conception and full-term pregnancies can increase your chances of conceiving and having a beautiful baby.

Stages of Fetus in Prenatal Development


Once you’ve found out you’re pregnant and have celebrated with social media posts and have rejoiced over the news, it’s time to understand what’s going on inside the womb.



About eleven days to two weeks after a woman's period, she is fertile and releases eggs. If a male sperm connects with it, it attaches to the uterine wall. At this point, the sex of the baby is determined by the male whose sperm will supply a Y chromosome for a boy or an X chromosome for a girl. During this time, the baby will be called an embryo.

1st Trimester (0-13 Weeks)


The 1st trimester is the most crucial time in fetal development, for the baby's organs, are developing. Miscarriages happened during this time, so it's important to take care of yourself.

Many changes to the mother’s body occur during the first four months of pregnancy: morning sickness (which can happen at any time), fatigue, mood swings, breast tenderness, and heartburn to name a few. There is usually little to no change to the outside of the body.

1st Month


The embryo develops a sac around it for protection while placenta transfers nutrients to the baby and wastes from the baby. At this stage, the baby is about a quarter of an inch long. The baby’s facial features begin to develop along with his heart.

2nd Month


The embryo’s facial features, the ears and eyes, continue to develop. His limbs also start to grow, along with his brain, spinal cord, and nervous system. He is about an inch long and weighs approximately 1/30 of an ounce.

3rd Month


Arms, hands, fingers, feet, fingernails, toenails—all of these are fully formed during the third month of pregnancy. The embryo can fist his or her hands. All the organs and their systems are developing. While the reproductive organs are forming, a doctor cannot tell the gender of the baby yet. The child is about 4 inches long and weighs about an ounce. After this month, the likelihood of a miscarriage decreases significantly.

2nd Trimester (14 to 26 Weeks)

During this period, the morning sickness and fatigue should be lessening along with many of the other symptoms from the 1st trimester. However, new pregnancy signs will appear, such as backaches, headaches, hernia, and frequent urination. This is also the time when the doctor can determine the baby’s sex through an ultrasound and the female will see increased hair growth, increased breast growth, and a rosy look to the face (pregnancy glow).

4th Month

This is an exciting month because a baby’s heartbeat can be heard on a Doppler ultrasound, and the baby's sex can be determined by the doctor. The child continues to develop facial features while the nervous systems begin working. The fetus will be about 6 inches long and weigh about 4 ounces.

5th Month

During this month is when parents feel the child moving, exercising its newly formed muscles. Hair begins to grow on the child’s head as well as his back, shoulders, and temple. Your child will be about 10 inches long and weigh about a pound.

6th Month

Fingerprints and toeprints can be seen during this month. You will be able to feel movements, and your baby will react to stimuli like light and sound. Your child's length will be around 12 inches and he/she will weigh about 2 pounds. A baby born prematurely during this month might survive with intensive care.

3rd Trimester (27 to 40 Weeks)


Expectant parents prepare to welcome their baby to the world stage. The mother will begin to have shortened breath as the fetus grows larger, developing into a baby. The baby turns around and could arrive into the world starting at the 38th week if the pregnancy is a healthy one.

7th Month

The baby’s body continues to develop and mature. The child continues to react to stimulants, especially since its hearing is fully developed at this stage. The baby’s length will be about 14 inches while his weight will be anywhere from 2 to 4 pounds. A baby born prematurely during this month has a high likelihood of surviving.

8th Month


The baby’s eyesight, as well as other organs, is fully developed. Only the lungs will not be completely mature. He or she will be moving around more and will be about 18 inches in length and about 5 pounds in weight.

9th Month


The baby’s organs and other body systems are fully developed. The baby can move, see, and hear. He or she will turn upside down and drop into the pelvis region in preparation for delivery. The child will be about 18 to 20 inches long and weigh about 7 pounds when it is born.

Factors Affecting Conception

Biological Factors


Eating fast food and sweets may be enjoyable; but if you’re having problems getting pregnant, it’s time to re-evaluate your eating habits. A female’s weight plays a key role in being able to conceive. Being too far above or too far below a healthy weight can negatively affect the ability to have a baby. In fact, being obese, especially at an early age like 18 years, is the leading cause of infertility. Taking the time to eat healthily and to exercise can significantly increase the ability to reproduce.

But what about the other side of the coin? Women often feel pressured to stay thin and fall below a healthy weight. Doing this can also cause problems with fertility. The answer is to gain weight to increase egg fertility through healthy eating and moderate exercise.

Exercising too vigorously can cause ovulation to decrease, making conception difficult.

Environmental Factors


We can safely assume that the FDA is strictly limiting chemical contaminants in our food and drink, right? Sometimes. The truth is that pesticides, plastics, and tap water all contain chemicals that are like a fake estrogen and can cause infertility. So, it's a smart idea to buy organic food, avoid food and drink in plastic containers, and buy a filter that filters out the synthetic estrogen when trying to get pregnant. This fake estrogen is the same chemical in birth control, so that's how important it is to avoid it to aid fertility. 

Even some forms of plastics found in household products like personal care and beauty items can produce chemicals that cause early menopause or infertility in women. Many chemical-free personal items can be purchased to decrease the threat of barren womb.

Lifestyle Factors


1. Alcohol

If you like to consume substantial amounts of alcohol, you may want to curb this habit if you are seeking to become a mother. While moderate amounts of alcohol are okay, heavy drinking can disturb your natural ovulation thus making it difficult to be pregnant. Some experts believe that you shouldn’t drink at all if you are trying to get pregnant as it could keep you from reaching your pregnancy goal.

2. Smoking

We’ve all known for years that smoking is hazardous to your health, but did you know it can make you infertile? The chemicals in cigarettes can change DNA and cause infertility in both men and women. Even second-hand smoke has this effect. Kicking the habit is crucial to helping you and your mate conceive. 

3. Stress

Stress—we all have it, but it can prevent a much-wanted pregnancy. For men and women, stress negatively impacts estrogen and testosterone prohibiting reproduction. It's essential that you find ways todo-stress, like doing yoga or listening to soothing music. Taking the time to relax will increase the likelihood of becoming pregnant.


When discussing the topics of fertility and pregnancy, the adage is true: knowledge is power. Knowing what to do and when to do it can help you beat infertility, and understanding what happens in a female's body during pregnancy can assist you in conceiving and delivering a happy, healthy baby.