First Trimester (0 to 13 Weeks) The first trimester is the most crucial to your baby's development. During this period, your baby's body structure and organ systems develop. Most miscarriages and birth defects occur during this period. Your body also undergoes major changes during the first trimester.
The embryonic period is the most critical period of development because of the formation of internal and external structures. The critical periods of development for the organs are also discussed in the section on specific organ development.
The third trimester is brimming with rapid development of neurons and wiring. His brain roughly triples in weight during the last 13 weeks of pregnancy, growing from about 3.5 ounces at the end of the second trimester to almost 10.6 ounces at term.
In general, major defects of the body and internal organs are more likely to occur between 3 to 12 embryo / fetal weeks. This is the same as 5 to 14 gestational weeks (weeks since the first day of your last period).
Most birth defects occur in the first 3 months of pregnancy, when the organs of the baby are forming. This is a very important stage of development. However, some birth defects occur later in pregnancy. During the last six months of pregnancy, the tissues and organs continue to grow and develop.
Weeks 1 & 2
One of the greatest risks to pregnancy at this stage is a blighted ovum which causes about half of the miscarriages between two and six weeks (often before the woman knows she is pregnant).
Certain factors may might increase the chances of having a baby with a birth defect, such as: Smoking, drinking alcohol, or taking certain "street" drugs during pregnancy. Having certain medical conditions, such as obesity or uncontrolled diabetes, before and during pregnancy. Taking certain medicines.
Infections pose perhaps the greatest risk to the developing fetus' brain. Many seemingly harmless infections can seriously interrupt fetal development, including the formation and wiring of brain cells.
Neonatal cranial ultrasound is considered the gold-standard screening method for neonatal brain injury, for the detection of major or significant abnormalities of the brain, most notably severe IVH or cystic periventricular leukomalacia in the preterm infant.
The Embryonic Period
The rapidly growing organism implanted in the uterine wall is now called an embryo. The embryonic period is the most critical stage of prenatal development as the embryo is the most susceptible to harmful agents in the environment.
Parent Tip. Recent brain research indicates that birth to age three are the most important years in a child's development.
The heart of the baby starts to beat around the fifth week of pregnancy. To confirm the heartbeat of your baby, the doctor may conduct a non-stress test. The test monitors the heart rate of the baby and provides information about the potential threat, if any. A healthy heartbeat is between 110 to 160 per minute.
If you are more than 28 weeks pregnant they may attach you to a heart rate monitor which records a trace of the baby's heartbeat. You may also be given a button to push every time you feel the baby move. This can also be seen on the print out of the baby's heartbeat.
Advancing maternal age.
A woman's chances of giving birth to a child with Down syndrome increase with age because older eggs have a greater risk of improper chromosome division. A woman's risk of conceiving a child with Down syndrome increases after 35 years of age.
Low birthweight, premature birth, multiple birth, and infections during pregnancy are associated with an increased risk for many developmental disabilities. Untreated newborn jaundice (high levels of bilirubin in the blood during the first few days after birth) can cause a type of brain damage known as kernicterus.
The most common severe birth defects are heart defects, neural tube defects and Down syndrome.
Your provider may use ultrasound: To screen for birth defects, like spina bifida or heart defects. After an ultrasound, your provider may want to do more tests, called diagnostic tests, to see for sure if your baby has a birth defect. Birth defects are health conditions that a baby has at birth.
First trimester screening is a combination of fetal ultrasound and maternal blood testing. This screening process can help determine the risk of the fetus having certain birth defects. Second trimester prenatal screening may include several blood tests called multiple markers.
More than 80% of miscarriages occur within the first 12 weeks of pregnancy. After 12 weeks, the rate decreases rapidly (Dante et al, 2013; Houry and Salhy, 2014).
2: The germinal stage of human development begins with fertilization in a Fallopian tube and ends with implantation in the uterus. The germinal stage of development is the first and shortest of the stages of the human lifespan.