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1 to 4th Week. Pregnancy week by week

18/01/2022 Gynecology


  • MOM: When calculating the probable delivery date, the first week is considered as the first day of a woman's last period, so this week in a strict sense, you would still have your period. Counting this way is necessary since it is very difficult to know the exact day of ovulation and the exact day of conception.


  • It is crucial that, if you are looking to have a baby, you properly prepare your body for conception by avoiding the consumption of alcohol, drugs, tobacco, and you should maintain a healthy diet.


  • BABY: The baby itself has not been conceived yet, under this counting method.




  • RECOMMENDATIONS: Consult your gynecologist to verify your general health and receive personalized recommendations; your physician might prescribe the consumption of a supplement or additional vitamins, such as folic acid.




  • MOM: Continuing with the counting method previously mentioned, this week is when the body prepares for ovulation (if your cycle is regular of 28-30 days on average). Your body begins the ovulation process, releasing a mature egg while waiting for a sperm to fertilize it to start the implantation of the fetus.


In your body, the uterine wall prepares and begins to build the lining that will later become the baby's placenta, and that will nourish it for nine months.


This week, fertilization is likely to occur; however, it will not yet manifest in your body for a few more weeks.


  • BABY: When the sperm and the egg unite, the changes that define the baby's genetic material begin to occur immediately. Although you won't know in a few months, the gender of your baby is determined at this point.


  • Required studies: If you look to get pregnant, you can take an ovulation test to have sex on fertile days.







  • MOM: You will not yet present external symptoms that let you know that you are pregnant. If you have sought pregnancy, it is essential that you know that this week is where your baby is officially forming and implanting, so you should take care of your diet and closely follow the recommendations that your gynecologist has indicated.


  • BABY: Your baby is working hard! Since its conception, it has been working at the molecular level for its development. By the time it reaches the womb, it has the appearance of a ball with many divisions called a "Morula," which later and as it continues to carry out its process will be called "Blastocyst."


  • REQUIRED STUDIES: None. It's too early for a pregnancy test!


  • RECOMMENDATIONS: Iron is an essential component throughout pregnancy, and in preparation for future delivery, start consuming this vitamin by increasing the consumption of foods such as meat, green leafy vegetables, eggs, and beans.



  • MOM: This is the week when a false period may appear; it is different for each woman. This week would coincide with your period; however, in many cases, pregnant women perceive slight bleeding caused by the embryo's implantation since the endometrial tissue developed in the womb is highly vascularized (that is, with an ample blood supply). When your baby is implanted, it can cause slight bleeding, accompanied by mild abdominal cramps, and make you confused. Sorry, mom.


  • Once implanted, the baby triggers a chemical response in your body, causing the increase of a hormone called "Chorionic Gonadotropin" -hCG- (also known as Pregnancy Hormone). hCG's function is to help keep the inner wall of the uterus irrigated to feed the baby and send the message to the ovaries so that they no longer generate more cycles as your body enters the development phase. Stop, we already have an occupant!


  • Some symptoms that you may perceive are sleepiness, tiredness, tingling in the body, breast pain, all similar to PMS.


  • BABY: Your baby, now also known as an embryo, consists of two layers of cells that will continue to grow and develop into a beautiful baby.


  • At the same time, other structures continue to develop, especially the amnion that contains the amniotic fluid and will protect the baby throughout the pregnancy, and the yolk sac that will temporarily replace the placenta while it is being built.
  • Mommy, I’m only 0.1 cm long!


  • STUDIES: Now you can get your pregnancy test that will look to detect hCG. In a non-pregnant woman, this hormone is present in values​​of up to 4 mlU / m; however, this hormone doubles every two days in pregnant women. Here is a table to see the increase of this hormone during pregnancy:



hCG Increase

3 weeks (LP)

5 – 50 mIU/ml

4 weeks (LP)

5 – 426 mIU/ml

5 weeks (LP)

18 – 7,340 mIU/ml

6 weeks (LP)

1,080 – 56,500 mIU/ml

7-8 weeks (LP)

7, 650 – 229,000 mIU/ml

9-12 weeks (LP)

25,700 – 288,000 mIU/ml

13-16 weeks (LP)

13,300 – 254,000 mIU/ml

17-24 weeks (LP)

4,060 – 165,400 mIU/ml

25-40 weeks (LP)

3,640 – 117,000 mIU/ml

Non pregnant women

<5.0 mIU/ml

Women after menopause

9.5 mIU/ml


  • RECOMENDATIONS: We recommend that you perform the hCG blood test since this hormone is present in lower concentrations in the urine.


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