Know more about the fetus (Baby inside the womb)


Pregnancy is one of the most amazing biological processes of living beings. From the moment of conception up to labor, a number of wonderful things happen inside the womb. Babies undergo various morphological and functional changes during a period of nine months. Here’s an insight into your baby’s miraculous journey across three trimesters.

First Trimester

Weeks 1- 5: Formation of an embryo

Normally, fertilization is 14days after the last menstrual period. A female egg combines with a sperm initiating a very complex biological process. The genetic composition of the baby including the sex, intelligence, physical characteristics etc. are determined from that very moment itself.

At 5 weeks your baby is about the size of a sesame seed! The important organs such as the brain, spinal cord, heart, arms and leg buds start to develop. Now it is called an embryo. It receives nutrition and oxygen via the placenta and the umbilical cord.

Weeks 6-8

External organs like ears and nose start to take form. Limbs grow longer and fingers and toes begin to appear. The formations of eye lids and sex organs also happen. The baby acquires a regular heart rhythm.

Weeks 9-12: Formation of a fetus

Embryo now looks like a human and is called a fetus. It displays many reflexes with the help of newly created neuronal connections. It can make a fist, curl its toes, and clench its eye muscles. It has now grown up to 3 inches and normally weighs about one ounce.

Second Trimester

Weeks 13- 17

Most of the internal organs are now developed and they continue to mature. Its skeleton system starts to develop along with bones and muscles. Skin and sweat glands appear around the body. In addition, meconium is formed in the intestines of your baby. Now it weighs about 5 ounces and has a length of 4-5 inches.

Weeks 18-21

Fetal movements can be felt now. The baby is now active and its senses have developed. It can hear and swallow. The baby is covered by lanugo which is a form of fine hair. Its eyebrows, eyelashes, toenails, and fingernails are fully developed by now. Now your baby is about 6 inches long and weighs approximately nine ounces.

Weeks 22-28

During this period, the senses of the baby continue to develop stronger every day. Now it can hear, smell, taste, and feel very well. It can open eyes and blink. It sleeps and wakes up according to its own time table. He can be even dreaming!

The lungs have developed, but non-functional. The genital system is developed as well. Now the baby’s sex can be easily determined using an ultrasound. Your baby now weighs about 1.5 pounds and has a length of approximately 12 inches.

Third Trimester

Weeks 29-32

The baby’s head increases in size to accommodate the developing brain. Its lungs continue to mature. Sometimes practicing breathing movements can occur. Baby is more active and needs more nutrients to survive. It gains weight rapidly at a rate of about 1.5 pounds/week. It has grown up to about 16 inches now.

Weeks 33-36

The baby continues to mature in every aspect. Even if a preterm labor happens at this time, the baby will be just fine. Lanugo around its skin starts to fall off and its skin is smoother than ever. It will continue to grow in size and weight. It can be about 19 inches long and 6 pounds heavy.

Weeks 37-40

This is considered to be the “term” of pregnancy. The baby is fully developed and delivery can be expected at any time. The baby turns itself upside down to make delivery easy. If any other type of presentation happens like a breech presentation where buttocks come out first instead of the head, your Ob/Gyn might consider going into a C-section rather than a normal vaginal delivery.

By now your baby can be about 20 inches long and 7-9 pounds heavy. These numbers can vary from one baby to another. Assuming that everything goes smoothly without any complications, you will be proud parents to a healthy bundle of joy by this time!