It’s the 4th week of your pregnancy. You’ve been pregnant for one whole month. Normally, it is the time for next menstrual period, but your pregnancy will trigger some hormonal secretions that will prevent this from happening. During this period, more advanced development of your baby will take place.
Everything looks normal from the outside, but your body is undergoing great changes inside to accommodate growing baby in your womb. During this stage, fetus is at high risk for abnormalities, as the brain, heart, head, spinal cord, bones, muscles, tissues, and teeth of baby are developing. By the fourth week, blastocyst is firmly embedded in your uterus.
Body changes during 4th Week of pregnancy-
Fetal development during 4th Week of pregnancy-
The blastocyst is now a tiny group of embryonic cells. Blastocyst would have already made the journey from your fallopian tube into your uterus. Now, implantation will occur and blastocyst will develop into an embryo.
Placenta may become fully functional by the end of this week. But in the beginning, it will not be able to provide nutrients to developing foetus. During this period, yolk sac delivers nutrients to the foetus.
Placenta will produce hormones like human chorionic gonadotropin (hCG) to alert your ovaries to stop releasing eggs and increase the production of estrogen and progesterone.
The embryo is about 2 mm long, now. It has three layers:
Arm and leg buds may also begin their development during this period. Rudimentary blood begins to move through the main vessels.
This is a study on ‘Neglected symptoms of heart failure presented as peripartum cardiomyopathy: a case of maternal near-miss’. https://goo.gl/7b4E5H