It’s an amazing experience for a pregnant woman to feel a new life developing in her body, even though at some point she may not feel at her best along the way. Pregnancy differs from woman to woman, even from one pregnancy to the next. Some discomforts of pregnancy are temporary or don’t affect all women while other symptoms of pregnancy last for several weeks to months.
Dr. Draion Burch, at Magee-Women’s Respiratory Hospital at the University of Pittsburgh, says pregnancy is a 10-month journey starting from the first day of a woman’s last menstrual period, which is about two weeks before conception happens. A typical pregnancy usually lasts about 40 weeks and is classified into three trimesters, and each trimester lasts between 12 to 13 weeks. Many changes occur in a pregnant woman’s body and the developing fetus during each trimester.
Conception and implantation
Two weeks after a woman has her period, her ovaries release a mature egg when she ovulates. When the released egg has travelled down the fallopian tube in the direction of the uterus, it will be fertilised for 12 to 24 hours. Conception occurs when an egg meets up with a sperm cell, which has made its way into the fallopian tube. At fertilisation, depending on whether the egg receives an X or Y-chromosome from a sperm cell, the sex of the fetus is determined. The baby will be a boy if the egg receives a Y chromosome and a girl if it’s an X chromosome.
According to the Cleveland Clinic, it takes about three to four days for the fertilised egg or embryo to move to the uterus where it will implant or attach to the uterine wall. The cells start to grow once the embryo is implanted, and they eventually become the placenta and the fetus, which is the tissue that transfers nutrients, hormones, and oxygen from the mom to the developing fetus throughout the pregnancy period.
Changes in the mother’s body during the first trimester (weeks 1-12)
In the early weeks of pregnancy, a woman will experience many symptoms as she adjusts to the hormonal changes of pregnancy. Even with all the change taking place inside of her body, there is very little change on the outside; it will be a few months before she begins to “show.”
For instance, a hormone that is present in a woman’s blood from the time of conception is human chorionic gonadotropin (hCG). The level of hCG can be detected in a woman’s urine about a week after her missed period, which is why a woman will have a positive pregnancy test so soon at home.
Changes in hormones, including hCG and rising estrogen, can contribute to morning sickness—waves of nausea and vomiting. These feelings can occur any time of the day despite being called “morning” sickness.
Some other common effects that occur during the first trimester include feeling more tired than usual, a symptom that has been linked to rising levels of the hormone progesterone. In addition, her uterus is also beginning to develop, which presses on her bladder leading to frequent urination.
A pregnant woman’s breasts will feel more tender and swollen in the early stages of pregnancy. Her areolas, the skin around each one of her nipples will enlarge and darken. Her digestive system may slow down to increase the absorption of beneficial nutrients. A pregnant woman’s heartbeat will increase to pump additional blood to the uterus. She will also begin to experience emotional lows and highs that will affect her for the remainder of her pregnancy.
Development of the embryo/fetus in the first trimester
From conception until eight weeks into the pregnancy, the baby is called an embryo, and after eight weeks of gestation, it is called a fetus. According to the American College of Obstetricians & Gynaecologists (ACOG), the lungs and heart begin to develop during the first few weeks. The legs, arms, brain, nerves, and spinal cord are also beginning to form during the first month of pregnancy.
The embryo is about the size of a pea around one month into gestation and will grow to the size of a kidney bean around the second month. Eight to ten of the main organs will have formed by the end of the second month. The bone and muscles are beginning to grow, including fingers and toes and buds for future teeth. The skin is almost transparent, and the intestines begin to form.
According to Dr. Burch, pregnant women should not take harmful medication at this stage of pregnancy.
Changes in the mother’s body during the second trimester (weeks 13 – 27)
A woman’s body has mostly adjusted to the changing hormone levels by the second trimester, so some of the unpleasant effects of early pregnancy may improve or go away. Energy levels may increase, and sleeping may get easier in the second trimester.
While nausea and vomiting may get better or go away, other symptoms may crop up as the fetus continues its growth and development. Dr. Burch said women experience more pelvic pressure as the baby bump appears and the uterus develops. The skin on her growing belly may itch as it stretches. Pregnant women also experience back pain as the fetus grows and the woman gains more weight.
A first-time mom may feel the first flicking movements of the fetus between the 16th and 18th weeks of pregnancy, which is known as quickening.
Dr. Burch encourages his patients to take a mini vacation, a weekend getaway or a baby-moon after the 20th week, which usually marks the halfway point of pregnancy. Some health professional may discourage travel after the 36th week.
Development of the fetus in the second trimester
The fetus grows quickly and will be between three and five inches long. If the parents want to know, an ultrasound may reveal the sex of the baby sometime between 18 and 22 weeks.
The eyebrows, fingernails, eyelashes, and neck all form in the fourth month of pregnancy. In addition, the skin has a wrinkled appearance, and the hands and legs can bend. According to ACOG, the fetus can swallow and hear, and the kidneys start working and can produce urine.
The fetus is more active in the fourth month of pregnancy and women may be able to feel its movement. A waxy coating (known as vernix) and fine hair (called lanugo) protect and cover the thin fetal skin. The fetus also sleeps and wakes on a regular circle.
The hair begins to grow, the brain is rapidly developing, and the eyes start to open by the sixth month of pregnancy. The lungs of the baby are formed but don’t function yet.
Changes in the mother’s body in the third trimester (week 28-40)
In the third trimester, a pregnant woman’s expanding uterus pushes against her diaphragm, making her feel short of breath because the lungs have less room to expand. As she retains more fluid and her blood circulation slows, her hands, feet, ankles, and face may swell. As the joints relax in preparation for delivery, she may also have more backaches and experience pain in the hips and pelvis.
The baby will drop down in her abdomen toward the end of the third trimester. As they prepare for breastfeeding, the breasts may experience some leakage of colostrum, a yellow liquid. As the woman gets closer to the delivery date, a false labour known as Braxton-Hicks contractions may begin to occur.
Women may be exhausted, and it becomes harder to find a comfortable sleeping position during the final weeks of pregnancy. As delivery approaches, some women may feel like they can’t wait for it to end while others love the experience of being pregnant.
Development of the fetus in the third trimester
The fetus continues to grow and can respond to sound and light by the seventh month of pregnancy. Its eyes can now open and close.
The fetus gains weight quickly during the eighth month of pregnancy. The skull remains flexible and soft to make a smooth delivery. The fetus can hiccup, and more parts of the brain are formed.
In the ninth month of pregnancy, the fetus is preparing for birth by turning into a head-down position into woman’s pelvis. The fetus continues to gain more weight rapidly, and the lungs are completely mature to prepare for functioning on their own.