Week 5 of Prenatal Development

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Made by Serif

What is happening in my body? It has been 5 weeks since conception, and you are considered 7 weeks LMP by your obstetrician. Last week, we learned how the heart began to beat, the brain began to form, sensory organs started to grow, and the pharyngeal arches appeared and began to give rise to multiple important structures throughout the body. Since your period is now 2 weeks late, you probably know for certain that you are pregnant. As growth continues to occur within you, it's common to continue to feel all of the symptoms listed in prior weeks in addition to the following, and as always, every pregnancy is different, so even if you experience none of these symptoms, you are considered completely normal. In addition to the previously described nausea, fatigue, and weight changes, this week you might begin to notice the following.

Facial Acne Facial acne is common during the first trimester while the level of hormones is increasing. Progesterone, which continues to be made in abundance, causes the glands in your skin to increase the production of oils. Beginning in the 2nd trimester, progesterone will no longer be produced by your ovaries and will instead be produced by the placenta, and acne often clears up after this time. Keeping your face clean with mild soaps, using oil-free moisturizers, and using water-based make-up can help to relieve acne problems. If you continue to have difficulties, consult with your doctor about over-the-counter or prescription treatments. Some medications are very harmful to your baby (for example, salicylic acids, Retin-A, tetracycline, topical retinoids, oral isotrentinoin such as Accutane, etc.), so be sure to check with your doctor before using any over-the-counter or prescription creams or pills for acne.

Increasing Urination It's a well-known fact that pregnant women have to use the bathroom more often. While some of the increase could be due to a slightly enlarged uterus, most of it probably has to do with the increased volume of blood in your body. The extra blood is filtered through your kidneys, and the extra waste produced by this is carried to your bladder. To avoid late night trips to the bathroom, try to avoid drinking too much an hour or two prior to bedtime. Talk to your doctor if you feel pain upon urination or constantly feel an urge to urinate, as this could signal a possible urinary tract infection.

Nipple Sensations As noted in previous weeks, it is normal to feel tenderness throughout the breasts as well as sore nipples. You may also feel tingling or burning sensations in the nipples that occur sporadically or constantly. This is thought to be due to your breast tissue stretching in order to accommodate the growth of milk ducts.

What is happening with my baby? This week, your baby continues to grow and develop organs at an amazing rate. Last week, he measured 1/4 an inch, and by the end of this week, he will be nearly 1/2 an inch long, which is about the size of a raspberry. He is still curled into a C-shape. In addition to the items explained in detail below, the intestines continue to lengthen, growing so fast that they will bulge into the umbilical cord. The liver is rapidly producing red blood cells at this point. Your baby will begin to move inside his watery home this week, although you won't be able to feel this for quite some time. These movements are mainly spontaneous muscle contractions, but the embryo is already showing some reflexes. For instance, if the embryo is touched near the mouth area, he will quickly draw back his head and twist his body.

Brain Development During this week, brain cells develop at the rate of approximately 250,000 cells per minute! The head will make up approximately one-third of the baby's length due to all of this growth. We learned that last week the brain was formed with 3 sections - the forebrain, midbrain, and hindbrain. This week, those 3 sections will divide to become 5. Perhaps the most interesting division is made in the forebrain, where a section called the "telencephalon" will form. The telencephalon is the largest part of a mature brain and will coordinate important functions such as speech, communication, movement, sense of smell, memory, and emotion.

Heart Development Last week, we learned that the heart started pumping blood at a rate of about 65 beats per minute. This week, however, the heart develops "pacemaker cells" that will regulate the heart's rhythm and increase the heartbeat to between 105 and 121 beats per minute. The S-shaped tube that made up the heart last week begins to pinch in several places and bulge in others, and this week we will see the early beginnings of the mature 4-chambered heart.

Lung Development This week, 2 lung "buds" form, which will give rise to the right and left lungs. As the lungs grow, they are already divided into 2 lobes on the left and 3 on the right, looking similar to adult lungs. The bronchial tubes and air passages, which will carry oxygen from the windpipe and into the lungs when the baby is born, are well underway at the end of this week.

Arms and Legs The arms first begin their development by the beginning of this week, and what at first begins as a small bud off of the body of the embryo will slowly elongate and begin to pinch at the tip, where the hand will eventually develop. Two days after the arm development has begun, the legs begin to develop in the same way - beginning as a bud and becoming elongated with a pinched end.

Facial Features As this week begins, your baby's facial features already begin to appear. Most of the facial structures are formed when a sensory "placode" (a thickened area of skin that will become a sensory organ) starts to form a pit, growing deeper and deeper until the structure is the right size for detailed development to take place.

Eyes The eyes begin their formation on either side of the baby's head. They will slowly migrate toward the front of the face over the next few weeks. Eye formation begins when the eye placodes dip in toward the brain. At the same time, the baby's brain forms small bumps that lengthen toward the forming eye placodes. These two structures meet, forming the optic stalk that will connect the eye to the brain permanently. Soon thereafter, the retina and lens of the eye begin to form. The retina, which has some color to it, can be seen through the paper-thin skin of the embryo at this stage.
Ears The beginning of each ear is formed this week, as the ear placodes on either side of the embryo's face form pits. These pits will slowly begin to develop into the structures that will be needed for hearing and equilibrium (balance).
Mouth The mouth is one facial structure that does not form from a placode. Instead, it takes shape as other facial bones (the chin, upper jaw, and nose) begin to form. The mouth at first appears wide, but the opening will shrink as these other facial structures change over the next few weeks. The tongue is already visible at this stage.
Nose The nose begins formation this week, as nasal placodes sink into the face to form 2 pits, soon to become nostrils. At first, the nostrils appear widely spaced, but they will move closer together over the next few weeks as well.