The first day of your menses is considered Day 1 of your menstrual cycle or The Last Menstrual Period (or LMP). It is important for knowing how old your baby is because you may not remember when you last had sex, or may have had sex several times so it is difficult to pinpoint when you got pregnant. It is also almost impossible to know when you ovulated or when the egg was fertilized by the sperm. It is essential to remember that if you base your baby's age on the LMP, it is usually 2 weeks older than your baby's actual age because ovulation happens 2 weeks after your LMP or on Day 14 to 16 of your menstrual cycle.

Ovulation happens between 12 to 16 days after the first day of your menses. This happens when a mature follicle releases an egg into the fallopian tubes. The egg can survive for only 24 hours after it is released. This is an important window especially for couples who are trying to conceive.

Fertilization happens when a sperm penetrates the released egg. The days that follow fertilization are among the most active times of development during pregnancy. This is why it is important to have supplementation even before you find out you are pregnant.

Once firmly in place, the ball of cells divide into 2 groups. One group will continue to differentiate into your baby, while the other group will become the placenta-–the structure that provides nourishment to your baby.

The amniotic sac or the bag of water is formed during this time. It is a water-filled water that will keep your baby safe from getting hurt if you experience 

Your baby resembles a tadpole more than a human. 

Arm and leg buds are developing.

The amnion is beginning to surround the body stalk which will later become the umbilical cord.

The circulatory system is beginning to form, and cells in the tiny "heart" will start to flicker this week.

Your baby is approximately 3mm long, the size of a sesame seed. It may be visualized and measured through ultrasound.

Your baby's nose, mouth and ears are starting to take shape, and their intestines and brain are beginning to develop.

The hearbeat is almost always visible on ultrasound.

Your baby is the size of a lentil.

Your baby has doubled in size since last week, but still has a tail, which will soon disappear. Little hands and feet that look more like paddles are emerging from the developing arms and legs.

Your baby is the size of a blueberry.

Your baby has started moving around!                                           Although you'll have to wait until the 18th to 20th week to feel it. 

Nerve cells are branching out, forming primitive neural pathways, these are necessary for your baby to feel. 

Breathing tubes now extend from their throat to their developing lungs.

Your baby is the size of a kidney bean. 

The crown rump length or the distance between the head to the butt is approximately 22mm. 

Fingers and toes become more visible, and the arms can now start to bend at the elbows.

The upper lip is complete, and the external ears form definitive elevations on either side of the head.

Your baby's basic anatomy is developing (they even have tiny earlobes now), but there's much more to come. Their embryonic tail has disappeared and they weigh just a fraction of an ounce but are about to start gaining weight fast.

Your baby is the size of a grape.

Your embryo has completed the most critical portion of development. Their skin is still translucent, but their tiny limbs can bend and fine details like nails are starting to form.

Your baby is the size of a kumquat

Your baby is almost fully formed. They're kicking, stretching, and even hiccupping as their diaphragm develops, although you can't feel any activity yet.

Your baby is the size of a fig.

Your baby continues to grow very fast!

Areas for bone formation and development appear in most bones, and your baby's fingers and toes have now differentiated.

Skin and nails develop, while patches of hair appear.

The external genitalia show definitive signs of being a boy or a girl, although it won't be seen on Ultrasound until the 18th to 20th week at the earliest.

This is the last week of your first trimester. Your baby's tiny fingers now have fingerprints, and their veins and organs are clearly visible through their skin. 

If you're having a girl, her ovaries contain more than 2 million eggs.

Your baby is the size of a pea pod.

Your baby's brain impulses have begun to fire and they're using their facial muscles. Their kidneys are working now, too. If you have an ultrasound, you may even see them sucking their thumb.

The neck is getting longer and the head more erect

Hair may start growing on top of the head as well as eyebrows

Soft, downy hair called lanugo may also be seen to grow all over the body

Your baby is the size of a lemon.

Your baby's eyelids are still fused shut, but they can sense light. If you shine a flashlight on your tummy, they'll move away from the beam. Ultrasounds done this week may reveal your baby's sex.

Your baby is the size of an apple.

The patterning on your baby's scalp has begun, though their hair isn't visible yet. Their legs are more developed, their head is more upright, and their ears are close to their final position.

Your baby is the size of an avocado.

Your baby can move their joints, and their skeleton – formerly soft cartilage – is now hardening to bone. The umbilical cord is growing stronger and thicker.

Your baby is the size of a turnip.

Your baby is flexing their arms and legs, and you may be able to feel those movements. Internally, a protective coating of myelin is forming around their nerves.

Your baby is the size of a bell pepper.

Your baby's senses – smell, vision, touch, taste and hearing – are developing and they may be able to hear your voice. Talk, sing or read out loud to them, if you feel like it.

Your baby is the size of an heirloom tomato.

Your baby can swallow now and their digestive system is producing meconium, the dark, sticky goo that they'll pass in their first poop – either in their diaper or in the womb during delivery.

Your baby is the size of a banana.

Your baby's movements have gone from flutters to full-on kicks and jabs against the walls of your womb. You may start to notice patterns as you become more familiar with their activity.

Your baby is the size of a carrot.

Your baby now looks almost like a miniature newborn. Features such as lips and eyebrows are more distinct, but the pigment that will color their eyes isn't present yet.

Your baby is the size of a spaghetti squash.

Your baby's ears are getting better at picking up sounds. After birth, they may recognize some noises outside the womb that they're hearing inside now.

Your baby is the size of a large mango.

Your baby cuts a pretty long and lean figure, but chubbier times are coming. Their skin is still thin and translucent, but that will begin to change soon too.

Your baby is the size of an ear of corn.

Your baby's wrinkled skin is starting to fill out with baby fat, making them look more like a newborn. Their hair is beginning to come in, and it has color and texture.

Your baby is now the same weight as an average rutabaga.

Your baby is now inhaling and exhaling amniotic fluid, which helps develop their lungs. These breathing movements are good practice for that first breath of air at birth.

Your baby is the size of a bunch of scallions.

This is the last week of your second trimester. Your baby now sleeps and wakes on a regular schedule, and their brain is very active. Their lungs aren't fully formed, but they could function outside the womb with medical help.

Your baby is the size of a head of cauliflower.

Your baby's eyesight is developing, which may enable them to sense light filtering in from the outside. They can blink, and their eyelashes have grown in.

Your baby is the size of a large eggplant.

Your baby's muscles and lungs are busy getting ready to function in the outside world, and their head is growing to make room for their developing brain.

Your baby is the size of a butternut squash.

Your baby is surrounded by a pint and a half of amniotic fluid, although there will be less of it as they grow and claim more space inside your uterus.

Your baby is the size of a large cabbage.

Your baby can now turn their head from side to side. A protective layer of fat is accumulating under their skin, filling out their arms and legs.

Your baby is the size of a coconut.

You're probably gaining about a pound a week now. Half of that goes straight to your baby, who will gain one-third to half their birth weight in the next seven weeks in preparation for life outside the womb.

Your baby is the size of a large jicama.

The bones in your baby's skull aren't fused yet. That allows them to shift as their head squeezes through the birth canal. They won't fully fuse until adulthood.

Your baby is the size of a pineapple.

Your baby's central nervous system is maturing, as are their lungs. Babies born between 34 and 37 weeks who have no other health problems usually do well in the long run.

Your baby is the size of a cantaloupe.

It's getting snug inside your womb – but you should still feel your baby moving as much as ever. Your baby's kidneys are fully developed, and their liver can process some waste products.

Your baby is the size of a honeydew melon.

Your baby is gaining about an ounce a day. They're also losing most of their lanugo hair that covered their body, along with the vernix caseosa, a waxy substance that was protecting their skin until now.

Your baby is the size of a head of romaine lettuce.

Your due date is very close, and though your baby looks like a newborn, they're not considered full-term until 39 weeks. Over the next two weeks, their lungs and brain will continue to mature.

Your baby is the size of a bunch of Swiss chard.

Are you curious about your baby's eye color? Their irises aren't fully pigmented at birth, so their eyes could change color up until they're about a year old.

Your baby is the size of a leek.

Your baby's physical development is complete, but they're still busy putting on fat and growing bigger.

Your baby is the size of a mini watermelon.

If you're past your due date, you may not be as late as you think, especially if you calculated it solely based on the day of your last period. Sometimes women ovulate later than expected.

Your provider will continuously assess your pregnancy to make sure you can safely continue your pregnancy.

Your baby is the size of a small pumpkin.

Your baby is now considered late-term. Going more than two weeks past your due date can put you and your baby at risk for complications, so your provider will probably talk to you about inducing labor. They may perform a non-stress test (NST) to monitor your baby's fetal heart rate and your contractions to make sure your baby isn't in any distress.