妊娠週数ガイド

妊娠1週目 妊娠1週目は、妊娠という長い道のりの土台が作られる、まだ目には見えない時期です。この週は、厳密にはまだ受精はしていませんが、体は新しい命を迎えるための準備を整えています。子宮内膜が新しくなり、ホルモンが調整され、排卵に向けた準備が始まります。妊娠の実感や症状はまだないかもしれませんが、体の中では大きな旅立ちに向けて、静かに準備が進んでいます。

Week 2 is biologically the week of the "Big Meeting," meaning fertilization takes place. Technically, you are still at the very beginning of your pregnancy, but the most important date of the century is about to happen inside your body.

妊娠3週目 妊娠3週目は、妊娠という道のりの中で、目に見えないほど小さく神秘的でありながら、最も重要な時期のひとつです。この週、受精卵は急速に分裂しながら子宮へと進み、そこに着床しようとします。まだ妊娠を確信できていないかもしれませんが、お腹の中では新しい命を迎えるための大切な準備が着々と進んでいます。

妊娠4週目は、妊娠の道のりが正式に始まる大切な時期です。一般的にこの時期に生理の遅れに気づき、検査薬で陽性反応が出て妊娠が確認されます。赤ちゃんは今、約ポピーの種（1〜2mm）ほどの大きさです。現在は胚（はい）と呼ばれるこの小さな命は、成長を続けるために子宮にしっかりと根付いています。

Week 5 is when pregnancy starts to feel real. At this stage, your baby is about the size of a poppy seed (2 mm). It is no longer just a line on a test strip; you are in a process of change that resonates through every cell of your body. Your baby’s heart begins its first beat this week!

Week 6 is an exciting milestone in your pregnancy journey where things start feeling more real, and you may even see your baby’s heartbeat for the first time. Now about the size of a sweet pea (5-6 mm), your baby’s facial features and organs are beginning to take shape. Meanwhile, your body is going through significant hormonal changes to welcome its new guest.

Week 7 is a time when your baby’s development gains momentum and you begin to feel these physical changes more intensely. Your baby has doubled in size since last week! They are now about 10 mm long, which is roughly the size of a blueberry.

Week 8 is one of the most important milestones of your pregnancy. Your baby is technically preparing to transition from the embryo stage to the fetus stage. While your baby, now about the size of a raspberry (1.6 cm), continues to develop their heart and brain rapidly, this week may be a time when pregnancy symptoms like nausea and fatigue peak, testing your patience.

Week 9 is a major milestone in your pregnancy journey because your baby is now medically transitioning from an embryo to a fetus. While your baby’s development continues rapidly, reaching about the size of a grape (2.3 cm), you may feel pregnancy symptoms most intensely during this period as hCG hormone levels peak. Hang in there; the relief of the second trimester is just around the corner!

Week 10 is an incredible week, often considered a critical milestone in pregnancy. Your baby has reached about 30 mm in size, roughly the size of a plum. Almost all of their vital organs have finished forming, and they are now moving from the construction phase to the growth and maturation phase. For you, this is a time when clothes start feeling a bit tight and your pregnancy begins to show.

妊娠11週は、妊娠初期の終わりが近づき、赤ちゃんの成長が加速するとともに、あなたも少しずつ元気を取り戻し始める橋渡しのような週です。赤ちゃんは今、ライム（約4〜5cm）ほどの大きさになっています。

Week 12 is like a graduation week in your pregnancy journey. Congratulations! You have reached the end of the first trimester. This week, your baby has reached the size of a lime (5.4 cm). It is a very special period where you may feel a great sense of relief both physically and emotionally, as development now enters the maturation phase. With the end of this week, you will successfully complete your first trimester! Your baby is now fully ready and starting their growth marathon.

Week 13 opens the door to a brand new phase in your pregnancy journey. You have now officially entered the second trimester — congratulations! Your baby has reached the size of a lemon (about 7-8 cm) this week. This is a transition week where your body adapts better to pregnancy, your energy slowly begins to return, and most expectant parents start to feel more balanced. For your baby, it is now a time of rapid growth and strengthening. The vital organs are all in place; now, the details and fine-tuning begin. Movements are increasing, reflexes are developing, and that tiny body is becoming more defined every day. With week 13, pregnancy becomes more fluid; morning sickness may decrease, emotions may settle, and the enjoyable parts of this journey start to be felt more deeply. You are no longer just moving forward — you are growing.

14週目へようこそ！ついに、妊娠の「黄金期」とも呼ばれる妊娠中期に入りました。最初の3ヶ月間の疲れやつわり、体調不良に悩まされた日々も、ようやく落ち着いてきた頃でしょう。今週の赤ちゃんは、大きさがおよそレモン1個分（8.9cm / 42.5g）になり、顔の筋肉や腎臓といった大切な器官も成長を続けています。さあ、体力を回復させて、この大切な成長の時期を楽しみましょう。

15週目は、妊娠中の「ハネムーン期」と呼ばれる時期の真っ只中です。赤ちゃんはリンゴやオレンジくらいの大きさ、つまり約10cmほどの長さに成長し、お腹の中で外の世界を探索し始めています。この時期、赤ちゃんの骨格の発達が加速し、動きもよりスムーズになっていきます。あなたにとっても、妊娠を身体でしっかりと感じられるようになり、かつエネルギーに満ちあふれた素晴らしい時期です。

Week 16 is a major highlight of your pregnancy journey. At this stage, you may begin to feel your baby’s first movements, which are often described as light flutters or bubbles. Your baby is now the size of an avocado and is moving energetically, measuring approximately 11-12 cm in length.

17週目へようこそ！赤ちゃんは今、大きなザクロ（約13cm）くらいの大きさです。今週から赤ちゃんの体は脂肪を蓄え始めます。これは、あの可愛らしい「むちむち」とした体つきの準備が始まったということです。ママにとっては、食欲が増してエネルギーが湧いてくる時期ですが、腰の痛みを少しずつ感じ始めるかもしれません。

18週目へようこそ！今週は、妊娠期間中の大きな節目の一つである精密超音波検査の時期に入ります。赤ちゃんの大きさは、ちょうどさつまいもくらいです。あなたの声をはっきりと聞き取れるようになり、お腹の中で小さな指をしゃぶって過ごしています。

妊娠19週目へようこそ！折り返し地点まであと少しですね。赤ちゃんは今、大きなマンゴーやトマトくらいの大きさ（約15cm）になりました。今週、赤ちゃんの肌は「胎脂（たいし）」と呼ばれる特別な物質に包まれ始め、皮膚を保護するようになります。お母さんは食欲が増す一方で、腰の痛みや胸やけを感じやすくなる時期です。

Congratulations! You have reached the halfway point of your pregnancy. Week 20 is a major milestone where your baby is now the size of a banana. You will notice their movements are evolving from tiny flutters into distinct kicks as they grow stronger. This is an important time for both celebration and monitoring your baby’s health in detail.

21週目へようこそ！おめでとうございます。ついに折り返し地点を過ぎ、妊娠後半期がスタートしました。赤ちゃんは今、大きなニンジンほどの大きさになっています。今週は赤ちゃんの消化器系がさらに発達し、胎動もよりはっきりと、リズムよく感じられるようになるでしょう。

Welcome to week 22! Your baby is now about 14-15 cm long, roughly the size of a coconut or a papaya. This week, your baby’s appearance is like a miniature version of how they will look at birth. For you, it is an interesting phase where your appetite increases, but you may also start experiencing forgetfulness and clumsiness, often called pregnancy brain.

妊娠23週は、妊娠期間において非常に重要な節目です。医学的には、この週は赤ちゃんが子宮の外の世界に適応する力を持ち始める生存可能限界（バイアビリティ）の始まりとされています。現在の赤ちゃんの大きさは全長約29cm、体重は約500gほどで、なすや大きなマンゴーくらいのサイズです。

Week 24 is a wonderful week as you approach the end of your second trimester and your baby has now reached the size of an ear of corn. This week marks a medical milestone with the start of the glucose screening test period, while your baby’s lungs speed up their development to prepare for the outside world.

妊娠25週 妊娠25週は、妊娠中期の終わりに近づき、赤ちゃんが急速に体重を増やして、外の世界に対して一人の人間のように反応し始める時期です。赤ちゃんの大きさは現在、身長が約34.6 cm、体重が約660 gほどで、カリフラワーや中くらいのメロンと同じくらいのサイズです。この時期、赤ちゃんの肺や血管は発達を続け、外の世界に出るための準備を整えています。

Welcome to week 26! You are nearing the end of your second trimester. Your baby is now about 35 cm long. The biggest highlight in your baby's world this week is finally opening their eyes!

With week 27, you are entering the Third Trimester, the most exciting and final stretch of your pregnancy. This week is a medical and biological milestone, as your baby’s chance of survival in the outside world has now risen above 90%. Your baby is now about the size of a cauliflower or a large head of lettuce (approximately 36.6 cm / 875 grams).

Week 28 officially marks the start of your third trimester. This week is a major milestone as your baby’s chance of survival is now very high, and your body begins practicing for labor. Your baby is currently about the size of a large eggplant.

Week 29 is an exciting stage as you move deeper into the third trimester and prepare for the grand finale of your pregnancy. This week, your baby has reached the size of a butternut squash or a large cauliflower (about 38-39 cm and 1.1-1.2 kg), and you may begin to feel the physical weight more clearly. Every movement becomes more meaningful, and every preparation feels more real. For your baby, this is a week of perfecting survival skills. While their lungs gear up to breathe the air of the outside world, their brain continues to weave a complex network with billions of new neurons. They are no longer just a growing life inside you; they are a tiny individual with their own character, reacting to light, sound, and even the flavors of the food you eat. Your body, meanwhile, moves into a mode of preserving its reserves. As your blood volume approaches its peak, your heart and lungs work harder than ever. Week 29 is a time when patience, physical endurance, and the silent bond you share with your baby are felt most strongly. You have traveled most of the way; now, each passing day brings you one step closer to the miracle.

Week 30 is a time when you are approaching the final stretch of your pregnancy journey and preparations are becoming more serious. Your baby is now as heavy as a large cabbage and is about 40 cm long. This week is a stage where your baby begins to react to the outside world not just physically, but mentally as well. For you, while managing increasing back pain and sleeplessness, the countdown to the day you hold your baby is picking up speed. Every kick is now stronger, and every movement is felt more clearly.

Week 31 marks a significant period in the third trimester as the countdown to delivery becomes more tangible. You have successfully navigated the majority of your pregnancy. This week is a crucial filling-out phase for both you and your baby. Your bump is now much more prominent, and while your physical activity might have slowed, your mind is likely occupied with thoughts of your baby's arrival. For your baby, this week involves major advancements in perceiving the world. They are refining their five senses in preparation for life outside the womb. While brain connections develop at a rapid pace, fat stores are accumulating to give them a fuller baby shape. Pregnancy reaches a higher physical intensity during week 31. You may experience shortness of breath, abdominal pressure, and sleeplessness; however, every strong kick is a sweet reward that reminds you of the purpose of this journey. You are nearing the end now, and each day brings you one step closer to the miracle you will soon hold in your arms.

Week 32 marks the final stretch of your pregnancy journey, a significant phase where physical changes and anticipation converge. Your body is now making essential preparations for birth, and your abdomen may feel increasingly tight as the uterus expands. For your baby, this period is dedicated to growth and maturation. Now measuring approximately 42 cm, your baby is the size of a squash. At this stage, brain cell connections are forming rapidly, and the immune system is establishing its first line of defense by acquiring antibodies from you. With week 32, the focus shifts toward the final countdown as you prepare for your new arrival.

Week 33 is a stage in the final stretch of your pregnancy where your baby is nearly ready for the outside world, though space inside the womb is getting quite tight. This week, your baby is about the size of a pineapple. While your body performs important rehearsals for birth, your baby’s immune system and bone structure are beginning to reach their strongest form.

妊娠34週目は、妊娠期間の最終段階に入り、期待と身体的な負担が同時に増していく時期です。赤ちゃんの大きさはメロン1個分ほどになり、体重は約2100〜2300グラムに達しています。この時期は医学的な節目でもあります。34週以降に生まれた赤ちゃんの多くは、医療的サポートを受けることで外の世界にうまく適応でき、長期的な健康上の問題が生じるリスクも非常に低くなります。

Welcome to week 35! You are now in the final stretch of your pregnancy, with birth only a few weeks away. Your baby is approximately 46 cm long and weighs 2400 grams, which is about the size of a honeydew melon. Although your baby’s physical development is nearly complete as they prepare for the outside world, you may feel your body getting heavier during this time.

Welcome to week 36! Your pregnancy has now reached the early term stage, meaning the risk of preterm birth has passed. Your baby, now approximately the size of a head of lettuce, is busy completing final preparations for birth as your due date approaches.

37週目へようこそ！おめでとうございます。あなたの妊娠は医学的に正期産とみなされる時期に入りました。これは、赤ちゃんの臓器が外の世界で助けを借りずに生きていけるほど十分に発達し、いつ出産が始まってもおかしくない状態であることを意味します。赤ちゃんの現在の長さは約48.5 cm、体重は約2.85 kgで、大きなメロンほどの大きさです。

38週目は、妊娠が正期産とみなされ、いつ出産が始まってもおかしくない非常にエキサイティングな時期です。赤ちゃんは外の世界に出る準備が完全に整っており、大きさは約50cm、重さは3100gほどで、スイカくらいのサイズになっています。今週のあなたの体の変化は、完全に出産プロセスに焦点を当てています。

39週目へようこそ！ついに妊娠が正式に正期産と見なされる時期に入りました。入院バッグを準備し、赤ちゃんに会えるまであと数日、あるいは数時間という最終段階にいます。赤ちゃんは現在、スイカほどの大きさで、平均体重は約3300g、身長は約50cmになり、外の世界に出る準備が完全に整っています。

Week 40 is the official finish line of your pregnancy journey, and your due date has finally arrived. This week, your baby has fully completed their development and is ready to enter the outside world at any moment. For you, it is a time when excitement and anticipation reach their peak. Your baby is now about the size of a pumpkin or a large watermelon.

Week 41 is a stage in your pregnancy journey where your expected due date has passed, a phase medically known as being post-term that requires a little extra patience. Your baby is now about the size of a watermelon and, although they are fully ready for life outside the womb, they haven't quite given up their cozy home just yet.

Week 42 is the final stage of pregnancy, known as post-term or overdue. This medical milestone marks exactly two weeks past your due date, a time when clinical monitoring becomes essential. Your baby is now about the size of a large watermelon and has completed their final preparations to enter the outside world from the womb.