Week 5: Your Baby's Heart Begins to Form

Your baby is now called an embryo and measures about 2mm, roughly the size of a sesame seed. This week marks the beginning of some of the most important development of the entire pregnancy.

The neural tube — which will become your baby's brain and spinal cord — is forming. The heart is also beginning to develop and will start beating later this week or early next week, even though it's still just a simple tube at this stage.

Tiny buds that will eventually become arms and legs are starting to appear, and the basic structure for the digestive system is forming too.

You may not look pregnant yet, but your body is already working hard. Rising levels of hCG (human chorionic gonadotropin) and progesterone are responsible for many of the early symptoms you might be noticing.

Your uterus is starting to expand, though it's still small enough to fit in your pelvis. Some women notice their clothes feeling slightly tighter around the waist, though this is more likely bloating than actual baby growth at this stage.

Common symptoms at 5 weeks include:

1. Fatigue and unusual tiredness
2. Nausea, with or without vomiting (morning sickness can start now)
3. Tender, swollen breasts
4. Frequent urination
5. Mild cramping as the uterus expands
6. Heightened sense of smell
7. Food aversions or sudden cravings
8. Mood swings

Not everyone experiences all of these, and the intensity varies a lot from person to person.

If nausea is making it hard to eat normally, focus on small, frequent meals rather than three large ones. Bland foods like crackers, toast, and rice are often easier to tolerate.

Make sure you're taking a prenatal vitamin with at least 400mcg of folic acid if you haven't started already — this is critical for your baby's developing neural tube.

Stay hydrated, even if plain water doesn't appeal to you right now. Try infusing it with a slice of lemon or ginger, both of which can also help settle nausea.

Gentle walking is a great option this week if you're feeling up to it. Listen to your body — if fatigue and nausea are intense, rest is just as valuable as activity right now.

Avoid starting any new high-intensity exercise routines. If you were already active before pregnancy, most moderate activities can usually continue, but check with your doctor about any specific concerns.

If you haven't already, this is a good time to:

1. Schedule your first prenatal appointment if you haven't already
2. Start or continue taking a prenatal vitamin
3. Stop drinking alcohol and smoking completely
4. Review any medications with your doctor to confirm they're pregnancy-safe
5. Cut back significantly on caffeine

Your first prenatal visit usually happens between weeks 6 and 10, so if you haven't booked it yet, now is a good time. This first appointment is typically longer than later ones and may include a full health history review, a physical exam, and sometimes an early ultrasound to confirm dates.

Write down any symptoms, questions, or concerns beforehand so you don't forget to ask.