ONSET OF PREGNANCY: EARLY FETAL DEVELOPMENT PHASES

March 22, 2017

Onset of pregnancy, Congratulations!! 

You must be very inquisitive about how your baby is growing and it is very common to have some concerns during the course of pregnancy. As every woman is different, so do pregnancy. Therefore, this is just a general guideline to highlight the developments happen in each phase and it may differ in each case. Ultimately, your doctor has the final say based on the investigations done him/her. Usually doctors do the blood test and ultrasound to monitor the health of your pregnancy.

 

Gestational age is the age of pregnancy from the last menstrual period, here all the time refers to the gestational age.

 

Week 1 and 2 (Conception time)
At this phase after your period has just ended, your body is ready for ovulation. So let us first briefly understand what ovulation is. Every month your body releases a mature egg which happens usually around 11-21 days from the first day of your last menstrual period and that egg is waiting for a sperm to get fertilized. So if you want baby, it is the suitable time period (11-21 days) but not only time period, for unprotected sex. 

 

Week 3 and 4 (Fertilization happened)

When the conception takes place sperm will penetrate a mature egg and form a zygote (fundamental of a new human being). Zygote has 46 chromosomes, equally divided between the father and the mother. These chromosomes decide the sex of your baby. Progesterone is the hormone which helps to maintain the pregnancy and in this phase it is the job of corpus luteum to produce it. Placenta is also started to form in this phase, its job is to nourish your baby throughout the pregnancy. Doctors can do the blood test, or urine test or ultrasound to check the health status of your pregnancy.

 

Week 5 and 6 (Embryo formed and developing)

In this phase, gestational sac can be seen through ultrasound. Here baby’s brain and spinal cord is started to form. Do checkout for progesterone level. By week 6, the average of progesterone level should be 10-29 ng/ml according to an article in January 2004 issue of “Gynecological Endocrinology”. The healthy level of progesterone helps to maintain a healthy functional placenta and nourish the embryo. By week 6, a formation of fetal pole is also seen through ultrasound. It is the first visible sign of a developing embryo. However, if you don’t see it, don’t worry there is a strong chance that in next ultrasound (after 3-7 days) you will see the fetal pole. Always remember, if you see any anomalies (Progesterone lower than 10 or fetal pole is not visible) do not stress yourself and do consult your doctor.

 

Week 7 and 8 (Cardiac activity is seen)
At the starting of week 7, placenta starts to take over the role of corpus luteum to produce progesterone. Baby’s eye lenses and arm buds started to form. A normal cardiac activity (90-120 beats per minute) in week 7, is expected. This heartbeat should be getting stronger in coming weeks 8 and 9. Once the cardiac activity is detected, the chances of health pregnancy to continue is around 80 %. By the end of week 8, baby’s eye would be visible. If there are any anomalies (cardiac activity is not seen), then don’t panic and it is quite possible that follow-up scan in 5-7 days should show the expected cardiac activity.


Week 9 and 10 (From embryonic stage to fetal stage)
By the end of week 9, a strong heartbeat (140-170 beats per minute) should be observed. A strong heartbeat is the sign of viability of fetus. If not observed, then go for another ultrasound in few days under the supervision of your doctor. Baby’s neck and toes will begin to form in this phase. By the end of week 10, placenta completely takes over corpus luteum to produce progesterone until the end of pregnancy. 


Week 11 and 12 (An official fetus)
Progesterone level has been increasing and its level in this phase should be around 15-60 ng/ml. hCG level (which can be known through blood test) will be at its peak (around 25,700- 288,000 mlU/ml) during this time and after week 12 it will likely start to decline. But the progesterone level will keep on increasing during the whole course of pregnancy. By the end of this week, baby’s genital will start developing. At this stage your baby might be around 2.5 inches long.

 


*Remember: This is just a general guideline, and it may differ in each case as every woman is different.

 

Check out our Early pregnancy phase Calculator and Analysis

 

Sources:
http://americanpregnancy.org/pregnancy-complications/early-fetal-development/
http://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/prenatal-care/art-20045302?pg=1
http://www.livestrong.com/article/81879-progesterone-levels-first-trimester-pregnancy/

 

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