4 Weeks Pregnant - What To Expect Your 4Th Week Of Pregnancy - Pregnancy Week By Week - 2023

4 Weeks Pregnant – What to Expect Your 4th Week of Pregnancy

It’s implantation time! Now no bigger than a poppy seed, though a whole lot sweeter, the ball of cells that will become your baby has completed its weeklong voyage down your fallopian tube and has claimed its berth in your uterus by tunneling into the sticky uterine lining. Nestled in your uterine home, this miniature miracle has established the cozy connection that will bind the two of you for the next eight plus months and forever after.

But that’s just the beginning of the action this week. In the works is the amniotic sac that your baby will call home sweet home. And at last! The sign you’ve been waiting for. Your little embryo starts to produce HCG, the just-for-pregnancy hormone that’ll turn your pregnancy pee test positively positive. You are officially expecting!

Though your embryo is only a tiny dot, it has already started to differentiate into three layers, each with its own job assignment. The inner layer, called the endoderm, will become the digestive system, the liver, pancreas, bladder, and thyroid gland.

The middle layer, the mesoderm, will grow into the heart, bones, kidneys, muscles, and blood vessels. The outer layer, called the ectoderm, will develop into the brain, nervous system, skin, hair, and eyes. It’s hard to believe, but by the end of your fourth week of pregnancy, all the building blocks for your baby’s vital organs are firmly in place.


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  1. Wow I am 5 weeks now but may ovulated late so i may be 4 weeks. Theres no sac yet they can only see thickness of my uterine lining 15.3mm and corpus luteum cyst. I just feel sore breast and uterine cramps.

  2. 4 weeks in on my second pregnancy. With the first one I had implantation bleeding at 8 weeks. With this one I had implantation bleeding the week before I tested. Is it possible that I'm actually farther than 4 weeks? I thought my last period started July 4th but maybe that was implantation bleeding? I'm in a new city and with Coronavirus the process seems to have changed. They didn't want to see me until 10 weeks along until they found out the meds I am currently taking. Last night I felt a new sensation of brief pain that felt like something going down a tube. Was that the baby moving from my side to the center? Can't wait for my appointment. Last pregnancy they wanted to see me immediately and every two weeks.

  3. Had my 2nd child late February this year and my cycle never got back to normal after that. I was with my significant other (father of my other 2 children) one time in June and I am pregnant AGAIN…. Its unfortunate because we wish we could be happy about it but we aren't. We didn't want more kids so soon and would have been ok with not having more. I know we risked it by having unprotected sex, but still I figured the odds were in our favor…. nope! So many couples try for months or even years before they conceive. Us, just once is enough. Our February baby was conceived by a one time only thing too but that was my fault. I thought day 11 was far enough away from ovulation. … Nope.

    I've been cramping and bleeding for 9 days now and it's not getting better, if anything it's getting worse. I haven't seen my doctor yet but I will tomorrow hopefully. I'm wondering if something is wrong because I never had this much pain and bleeding with the other pregnancies. I had 3 false periods in March so they can't judge gestational age by my last period cuz that would not be accurate. In my case do doctors add 2 weeks from when I had sex? Or do they add 2 weeks from when implantation started?

  4. I’m so nervous , my first pregnancy was a super early miscarriage at what would have been about 5 weeks … I’m now confirmed pregnant again and probably 4/5 and I’ve got similar cramps to the first time and worried I’m going to lose it again …. I’m 24 and super healthy if this happens again I’d have no idea how to feel and what to do … we got pregnant first go for first one and this one again, first go trying so I’m hoping my body can hold it …

  5. I found out im having my 3rd child , and definitely unplanned , i took a plan b … and honestly i dont know how it didnt work , im regreting even meeting that man.. im not ready and i feel really broken rn, i already going through it with 2 trying to get stable..

  6. I’m so nervous about this whole experience but excited at the same time. (Edit: ) I am actually 10 weeks and three days pregnant today) just saw my peanut today in the ultrasound he or she already looks like a full baby ! Amazing

  7. I had a chemical pregnancy last month and had a terrible pain at around 4 weeks and 6 days with a lot of heavy bleeding so I know I lost it. My period is late which means I should be 4 weeks and 3 days today, but I‘m scared to test! 😢

  8. My wife got pregnant , we went for strip test first it was positive then we went for beta hsg but it was slightly high like 2700 and it was 4 weeks. Then we went for ultrasound doctor said its too early it was 5th week and she just saw gestational sac nothing else . My question is why beta hag was raised ? Does it mean twins ? Or 2700 beta hcg value is normal in 4 weeks ?

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Written by Claire

Claire is our Community Manager here at New Moms Forum. A mom of two (almost grown-up babies), Claire has been building and operating community-based websites for almost 20 years. In her downtime, Claire enjoys spending time with her family and drinking copious amounts of red wine!

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