Knowing how her baby is developing in her womb helps a mother prepare for the miracle of birth. Development of the infant continues at a rapid pace in the fourth month. From fourth month until the baby's delivery, the mother needs to consume an extra 300 calories per day above her preconception intake to support the rapid growth and healthy development of her infant, according to Eleanor Whitney and Sharon Rolfes in "Understanding Nutrition."
Identification
The fourth month of pregnancy marks the beginning of the second trimester and includes weeks 14 to 17 of pregnancy. A normal pregnancy lasting 40 weeks is counted from the first day of the last menstrual period. A full term pregnancy, however, may range from 37 to 42 weeks. Trimesters last from 12 to 13 weeks, or about 3 months each.
Milestones
During the fourth month of pregnancy, rapid development of the infant continues with constant change and significant milestones achieved. Prenatal reflexes strengthen and mothers can feel arm and leg movements for the first time. The baby can swallow and hear, and the outer ear begins to develop. Eyebrows, eyelashes and fingernails form. The skin is covered with vernix, a waxy protective coating, and fine hair called lanugo, according to the American Congress of Obstetricians and Gynecologists website, ACOG.org. External sex organs have formed, the kidneys produce urine, and the infant can make facial expressions and sucking motions, according to MayoClinic.com.
Size at Four Months
Rapid development of the fetus continues throughout the fourth month. By the end of 16 weeks gestation, the fetus is 5 ½ inches in length and weighs about 4 oz., according to John Santrock in "Life Span Development." By the end of the fourth month or week 17, the fetus could be 6 to 7 inches long and weigh 5 oz., according to the American Congress of Obstetricians and Gynecologists.
Nutrition During Pregnancy
A mother's food choices affect both her own health and her infant's growth and development. A healthy pregnancy demands protein, folate, vitamin B12, vitamin C, iron and zinc. Essential fatty acids are needed for the growth, structure and function of the brain. Vitamin D and minerals such as calcium, phosphorous, magnesium and fluoride are needed for bone building, cell growth and blood production, according to Eleanor Whitney and Sharon Rolfes in "Understanding Nutrition." A pregnant woman can meet her nutrient needs through wise food choices. Her doctor may recommend an iron supplement or multivitamin during the second and third trimesters of pregnancy.
Timeline Considerations
To avoid confusion, it is important to pay particular attention to whether a timeline reflects weeks of pregnancy or weeks of gestation. Most medical sources base the timeline from the beginning of the menstrual cycle prior to conception. There is a difference of two weeks between timelines that refer to weeks of pregnancy and timelines that refer to weeks of gestation. There may also be slight differences among sources based on how the nine months of pregnancy are divided into days, weeks, months and trimesters.
References
- "Understanding Nutrition, Ninth Edition"; Eleanor Noss Whitney and Sharon Rady Rolfes; 2002
- The American Congress of Obstetricians and Gynecologists: How your baby grows during pregnancy
- MayoClinic.com: Fetal Development: The Second Trimester
- "Life-Span Development"; John Santrock; 1997
