Conceptual Options Pregnancy News: Fetal Development Timeline for Surrogates & Intended Mothers

Conceptual Options Pregnancy News: Fetal Development Timeline for Surrogates & Intended Mothers

The transformation from a tiny fertilized egg to a fully formed baby is awe-inspiring. Here’s a look at the major milestones babies in utero typically reach, from conception to birth, and approximately when they happen.

First trimester

Your baby-in-the-making is a ball of cells called a blastocyst. The blastocyst already contains a full set of DNA from you and your partner, which determines sex, eye color, and other traits.
The ball of cells has officially become an embryo and is about the size of a poppy seed. Over the next six weeks, all of your baby’s organs will begin to develop, and some will start to function.
Your baby’s tiny heart begins to beat – at twice the rate of yours. His entire “body” is only about the size of a sesame seed.
Facial features (like eyes and nostrils) are beginning to form, and little buds appear where arms and legs will develop.
Arms and legs are growing, and your baby now has little fingers, as well as a nose and upper lip. He’s moving quite a bit now, but you won’t feel it. He’s about 5/8 of an inch long and weighs hardly anything – four-hundredths of an ounce.
Eyes have developed, though your baby’s eyelids are fused shut for now. She’s lost her “tail” and is starting to look more human.
The embryo has become a fetus. His vital organs – such as kidneys, intestines, brain, and liver – are starting to function. Tiny fingernails and toenails are forming.
Your baby is almost fully formed. Her bones are beginning to harden, and her genitalia are developing externally. She can hiccup, though it’s too soon for you to feel it.
You can hear your baby’s heartbeat at a prenatal checkup.(You may already have heard it at an early ultrasound.) Your baby’s just over 2 inches long and weighs about half an ounce.


Second trimester

Your baby’s kidneys are producing urine, and he releases it into the amniotic fluid. He can make facial expressions and may have discovered thumb-sucking.
Your baby can see light that filters in from outside your womb, even though her eyelids are still shut.
Your baby’s sex may be detectable at your mid-pregnancy ultrasound, which typically happens between 16 and 20 weeks.
If you haven’t felt your baby move yet, you probably will in the next few weeks. It’ll take a couple of weeks longer for your partner and other people to feel your baby’s movements from the outside.


Your baby can hear your heartbeat and sounds that come from outside your body, such as your partner’s voice. Your baby might even be startled by a loud noise.
Your baby’s sense of movement has developed, so he can feel the motion if you dance. His sense of hearing continues to improve. You may sometimes be able to see him squirming under the surface of your belly.
Your baby’s taste buds are developing. Her brain is growing very quickly, and her hair may be growing, too. She’s almost a foot long and weighs just over a pound.
Your baby’s been doing “practice breathing” by inhaling and exhaling amniotic fluid, and if he was born now his lungs could function (with a lot of medical help). He can also open and close his eyes.


Third trimester

Your baby may be dreaming. She has eyelashes, and her eyesight is improving. She weighs about 2 1/4 pounds and is about 15 inches long, head to heel.
He’s grown cute little fingernails and toenails. He’s almost 17 inches long (head to heel) and weighs about 3 3/4 pounds.
If your baby’s born now, she’s considered “late preterm.” Healthy babies born at this stage usually do fine, though they need some care in the neonatal intensive care unit.
Your baby is now considered full-term. His lungs should work fine if he’s born now, but ideally he’ll stay in your womb a bit longer.
Your baby is due and fully ready for life outside the womb. The average weight of a newborn is about 7 1/2 pounds, and the average length is about 20 inches. If you go more than one or two weeks past your due date without delivering, your doctor may decide to induce labor.

Read more here about the Fetal Development Timeline for Surrogates & Intended Mothers