Your Baby Week by Week. A Pregnancy Guide

Transcription

1 Your Baby Week by Week A Pregnancy Guide

2 Your Baby: Weeks 1-8 This is the most critical period of the pregnancy. During the first week, the development of your baby starts immediately after fertilization (when the male sperm and female oocyte (egg) meet in and unite to form the zygote). If more than one egg is released from the ovary, twins may develop. The developing zygote has 46 chromosomes 23 from you and 23 from the father. These chromosomes will ultimately dictate the baby s gender, size, hair and eye color, etc. From there things happen quickly. These two cells start to multiply and will migrate from the tube where they met to the uterus where they will implant around week 4. The placenta then starts to develop which will supply all of the nourishment the developing fetus will need. Weeks three through eight are called the Emrbyonic Period. Most, if not all, of the major tissues and organs are formed during this time. During this time the neural tube (or spinal cord) will close. Taking folic acid supplements through prenatal vitamins will help prevent neural tube defects like Spina Bifida at this point in your pregnancy. By the end of this period, an ultrasound can be used to measure the crown-rump length from head to tail. And at 7-8 weeks, the embryo will measure mm, the size of a large almond. The limbs have started to develop and the heart is beating at around the 6 th week. At the completion of the Embryonic Period - the neural tube, the heart, and all major organ systems have formed. This entire process is called organogenesis.

3 Your Baby: Weeks 9-12 Now that the Embryonic Period is complete week 9 kicks-off a very rapid growth phase and the Embryo is now referred to as a Fetus. During this 4-week period the limbs continue to grow as the bones develop; the head becomes more round and is half the size of the entire body length. At week 9, the genitals start to differentiate into male or female and which will be completed by week 12. By the end of the Fetal Period, the fetus will measure mm (2-3 inches) or the size of an apricot.

4 Your Baby: Weeks The beginning of the second trimester brings with rapid growth this continues for the entire fetus except for the fetal head. The face becomes more defined with the eyes now lie directly on the front of the face, the ears have moved to their final location on the side of the head. The bones are formed completely and the skeleton can be seen well for the first time on x-ray. The fetus may start sucking its thumb and fetal movements will become coordinated. By the end of this four weeks, the fetus will measure approximately 9-14 cm (4-6 inches) and will weigh about 200 grams (just less than 1/2 pound) or the weight of a small potato.

5 Your Baby: Weeks The rapid growth slows down and the extremities become proportional to the rest of the size of the fetus. Lanugo (fine hair) and vernix caseosa form to cover and protect the skin. The spinal cord is now myelinated (the surface of many nerve fibers) and most importantly for you you may start to feel the baby move. This is called quickening. The fetus will weigh grams (1 pound) by the end of 20 weeks.

6 Your Baby: Weeks The head of the fetus is becoming more normal in size compared to the rest of the body. The fingernails, eyelids and eyebrows are well developed and the Lanugo darkens. The skin is more wrinkled due to not having much fat and the excess growth of the skin. The face and body take on the appearance of an infant seen at birth. Usually by the end of the 24 th week, the fetus will weigh grams (1-1/12 pounds) and is considered viable or able to live outside of the uterus should it be born at this point. This is not always the case, as the coordination between the central nervous and respiratory systems is not well organized.

7 Your Baby: Weeks During the beginning of the third trimester, the fetus continues to grow and the organ systems become better coordinated. The lungs are becoming more developed with the formation of the terminal sacs that will aid in oxygen exchange. The eyes can open between weeks, and the eyelashes are developed. The hairs on the scalp are growing in and the baby is now becoming chubby with the addition of additional fat deposits. The baby at this point will weigh grams (approximately 2 lbs) and will be 9 ½ to 10 ½ inches long.

8 Your Baby: Weeks The body continues to add fat and the skin is now pink. The toenails are present and the fingernails reach the end of the fingers. The male fetus testes will start to descend into the scrotum. The baby will weigh grams (2 ½ pounds) and will be cm or approximately 1 foot long.

9 Your Baby: Weeks The plump baby is getting ready for delivery. The toenails have reached the ends of the toes, the Lanugo has been completely shed, vernix continues to protect the skin, the testicles have reached the scrotum, the ovaries have not yet reached the pelvis (and may not before birth). The brain begins its myelination process

10 Your Baby: Weeks The baby is finally full-term and will weigh on average 3,200-3,600 grams or 6-7 pounds.

11 Your Baby: Weeks >40 Post-term delivery of the infant is common and your Obstetrician will discuss the risks of continuing the pregnancy beyond weeks due to concern for placental problems and large babies which may complicate labor and child birth.