GUIDE
Published on ·Updated on
Your baby is the size of a lemon — vocal cords are forming and fingerprints are now unique.
The final week of the first trimester brings some beautiful developments. Vocal cords are taking shape in the larynx — the very first hardware for the cries and coos you will hear in a few months. The fingerprints are becoming unique patterns that will last a lifetime. The head, which has been disproportionately large, is beginning to balance out as the body catches up in growth.
Be prepared from day one
“There's a host of reasons why prenatal care is important. The earlier that we can get patients seen, the earlier we can start interventions that can improve these longer-term outcomes.”
Your baby is about the size of a lemon — roughly 7.4 centimeters (2.9 inches) from crown to rump and weighing about 23 grams (just under an ounce). The body is growing faster than the head now, so proportions are becoming more balanced.
Vocal cords are forming in the larynx this week. The fetus will not make any sounds in utero (there is no air to vibrate), but the structures needed for crying, cooing, babbling, and eventually speaking are being built now. These tiny cords are among the most complex tissues in the body — delicate membranes that must vibrate with extraordinary precision to produce the range of human voice.
Fingerprints are becoming truly unique. The ridge patterns on the fingertips, which began forming weeks ago, are now developing into the one-of-a-kind whorls, loops, and arches that will remain unchanged for a lifetime. These patterns are influenced by both genetics and the random, unrepeatable conditions in the womb — the pressure of the fingers against amniotic fluid, the position of the fetus, the flow patterns of the fluid. This is why even identical twins have different fingerprints.
The fetus is very active — stretching, flexing, kicking, grasping, and somersaulting. It can now turn its head. The eyes, still fused shut, have moved to the front of the face. The body is covered in a fine, downy hair called lanugo, which helps regulate temperature by trapping a layer of warmth close to the skin. The kidneys are functioning and producing urine regularly, contributing to the amniotic fluid.
For a look at what happened last week, see our week 12 guide.
For many pregnant people, week 13 feels like emerging from a tunnel. The relentless nausea of the first trimester is easing, energy is returning, and the anxiety about miscarriage risk has lessened. It is not a dramatic overnight change — more like a gradual brightening.
Your appetite may return with surprising force. After weeks of eating only crackers and bland foods, you may suddenly crave full meals, diverse flavors, and larger portions. This is your body catching up on calories and nutrients it may have missed during the nausea-heavy weeks. Embrace it, but try to balance cravings with nutritious choices. Protein, iron, calcium, and omega-3s are all in high demand. With energy returning, this is also a great time to begin a regular pregnancy exercise routine.
Your bump may be visible now, especially by the end of the day when bloating adds to the uterine growth. The uterus is growing steadily and is palpable above the pubic bone. You may notice that your regular pants no longer button comfortably, even if you have not gained much weight.
Heartburn and acid reflux may make their first appearance around this time. Progesterone relaxes the valve between the stomach and esophagus, allowing stomach acid to creep upward. Eating smaller meals, avoiding lying down right after eating, and staying upright after meals can help. Antacids like calcium carbonate (Tums) are generally considered safe during pregnancy.
Every pregnancy is different. You may experience all, some, or none of these symptoms.
This is a week of transition and celebration. The first trimester is ending, symptoms are improving, and the excitement of sharing your news may be at its peak.
You have made it through the most symptom-heavy and anxiety-inducing phase of pregnancy. The first trimester is hard — physically, emotionally, and often secretly, since many people have not told anyone yet. Acknowledge what you have been through. You deserve it.
Whether it is a social media post, a family dinner, a phone call, or a card — sharing the news is one of the most exciting parts of pregnancy. If you work outside the home, you may also want to start planning when and how to tell your employer and colleagues.
The second trimester (weeks 14-27) is often called the 'golden trimester' because many people feel their best. Key milestones ahead include the anatomy scan (18-22 weeks), feeling the baby move (16-25 weeks), and the glucose tolerance test (24-28 weeks). Knowing what is coming helps you prepare.
With energy returning, this is an excellent time to establish a consistent exercise routine. Aim for 150 minutes of moderate activity per week — walking, swimming, prenatal yoga, or light strength training. Regular exercise reduces the risk of gestational diabetes, preeclampsia, and excessive weight gain.
As your skin stretches over the coming months, keeping it well-moisturized may help with comfort and itching. While no cream has been proven to prevent stretch marks (which are largely genetic and hormonal), regular moisturizing feels good and can reduce the dry, tight sensation as your belly grows.
When in doubt, call your provider. No question is too small during pregnancy.
Next week marks the official start of the second trimester — often called the "golden trimester" for good reason. Your baby will be able to make facial expressions, and many people feel a surge of energy and wellbeing.
Next up: Week 14. If morning sickness has lingered, our morning sickness guide covers late-first-trimester strategies. For a continued boost, see our pregnancy fatigue guide. Ready to share the news? Browse our pregnancy announcement ideas for creative inspiration. And look ahead to what the next several months hold in our second trimester guide.
This guide is for informational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider with any questions about your pregnancy.
