What are the different stages of pregnancy?

Even if you may not always feel your best at all phases of pregnancy, for a pregnant woman to sense a new life forming inside her body is an extraordinary experience. According to the Centers for Disease Control and Prevention, a pregnant woman carrying a single child should gain between 11 and 40 pounds (5 to 18 kilograms) by the conclusion of her pregnancy, depending on her pre-pregnancy weight.

But there are many other changes, and how pregnancy affects the body may vary greatly from person to person and even from one pregnancy to the next for the same woman. Some pregnancy symptoms endure for weeks or months, although others are transient or may not affect everyone the same way.

Dr. Draion Burch, an obstetrician and gynaecologist at Magee Womens Hospital at the University of Pittsburgh Medical Center, said, “Pregnancy is a 10-month experience.”

Normal pregnancies last around 40 weeks, beginning with the first day of the last menstrual cycle, which occurs approximately two weeks before conception. Each of the three trimesters of pregnancy lasts between 12 and 13 weeks. During each trimester, both the pregnant woman’s body and the growing baby undergo changes.

A paper published in July 2017 in the American Journal of Obstetrics and Gynaecology suggests that mothers and doctors should also recognise a “fourth trimester,” which is the 12-week period after birth during which babies are adjusting to life outside the womb and women are adjusting to motherhood and the ongoing changes to their bodies.


Approximately two weeks following a period, ovulation occurs, during which the ovaries generally produce one egg, but sometimes two or more. As the egg moves down the fallopian tube toward the uterus 12 to 24 hours after release, it may be fertilised by a sperm cell.

Fertilisation, or conception, determines the sex of the baby based on whether the egg gets an X or Y chromosome from the sperm cell. If the egg obtains an X chromosome, the resulting child will be a girl; a Y chromosome will result in a male.

According to the Cleveland Clinic, it takes around three to four days for the fertilised egg (or embryo) to migrate to the uterine lining, where it attaches or implants. Once the embryo is implanted, the cells begin to multiply, ultimately becoming the foetus and the placenta, which connects to the uterine lining. Throughout pregnancy, the placenta transfers oxygen, nutrients, and hormones from the mother’s blood to the growing baby through the umbilical cord.


During the first trimester, the mother experiences the following changes:

In the first trimester, as the body adapts to the hormonal changes of pregnancy, pregnant women may suffer a variety of symptoms. In the early weeks of her pregnancy, her body may not display many signs of pregnancy, but significant changes are occurring within.

Human chorionic gonadotropin (hCG) hormone, which appears in the blood shortly after conception, is one of the first alterations. About a week following a missing period, hCG levels may be discovered in the urine of a pregnant woman. Human chorionic gonadotropin is what a positive at-home pregnancy test detects.

Rising levels of hCG and other hormones, such as oestrogen, may be responsible for the nausea and vomiting associated with morning sickness, which is most prevalent in the first few months of pregnancy. Morning sickness may occur at any time of day, despite its name.

During the first trimester, a pregnant woman may feel more sleepy than normal, a symptom associated with increased levels of the hormone progesterone, which causes drowsiness.

As a result of growing levels of pregnancy hormones, breasts may feel more sensitive and swollen during early pregnancy. The skin around each nipple, the areolas, will change colour and expand.

The digestive tract of a pregnant woman may slow down to maximise the absorption of healthy nutrients. According to the Office for Women’s Health, diminished mobility of the digestive tract may also cause typical problems such as heartburn, constipation, bloating, and gas.

Many components of the body, including the heart, will work harder during pregnancy. In order to pump more blood to the uterus, which will deliver it to the foetus, the heart rate will rise.

In addition to physical changes, pregnant women may experience emotional highs and lows in the early and later months of their pregnancy. These feelings might vary from melancholy, mood swings, and forgetfulness to dread, anxiety, and elation.

First trimester embryo development:

From the time of conception until the eighth week of pregnancy, the growing infant is referred to as an embryo.

According to the American College of Obstetricians and Gynaecologists, the heart and lungs, as well as the arms, legs, brain, spinal cord, and nerves, begin to grow during the first month of pregnancy.

Burch said that the embryo would be around the size of a pea one month into pregnancy. The embryo has grown to the size of a kidney bean during the second month of pregnancy. Additionally, the ankles, wrists, fingers, and eyelids grow, bones emerge, and the genitalia and inner ear begin to form.

After the eighth week of pregnancy and until delivery, an embryo is referred to as a foetus.

Burch said that by the end of the second month, the majority of the foetus’ major organs would have developed. During this period of pregnancy, he said, it is crucial that women do not consume hazardous medicines or illicit narcotics. During the first trimester, the majority of miscarriages and birth abnormalities occur. According to the Mayo Clinic, between 10 and 20% of known pregnancies terminate in miscarriage, mostly because the baby is not growing appropriately. After the 12th week of pregnancy, the chance of miscarriage decreases dramatically, according to studies.

A pregnant woman may choose to get a noninvasive prenatal test as early as the 10th week of pregnancy (NIPT). According to MedlinePlus, this test analyses DNA from the pregnancy using a blood sample from the mother to predict the likelihood that the baby would be born with specific genetic disorders. In addition, the woman may determine the baby’s gender at this stage by supplying a blood sample for foetal DNA analysis. None of these examinations come into touch with or injure the foetus.

In the third month of pregnancy, the bones and muscles of the foetus begin to develop, tooth buds form, and fingers and toes expand. The formation of the intestines begins, and the skin is almost translucent.


During the second trimester, the mother experiences the following changes:

As the body adapts to the fluctuating hormone levels throughout the second trimester, the unpleasant symptoms of early pregnancy may diminish or vanish. It may become easier to sleep, and energy levels may improve.

Burch told Live Science that nausea and vomiting often improve and fade away. However, additional symptoms may emerge as the foetus continues to develop and grow.

Burch said that pregnant women would experience an increase in pelvic pressure, adding that the pelvis will feel as if it is being weighed down.

As the uterus develops beyond the pelvis, a noticeable baby bump forms, and the skin over the developing belly may itch as it strains, according to the OWH.

Burch said that as the baby becomes larger and the woman gains more pregnancy weight in the front of her body, she may have increased back discomfort. In a research published in the Journal of Personalized Medicine in 2020, it was determined that although the majority of pregnant women reported back discomfort, it was more severe in inactive women.

Burch said that a first-time mother may feel the first fluttering movements of the baby, known as quickening, between the 16th and 18th weeks of pregnancy. He said that if it is not the mother’s first pregnancy, she is more likely to feel the baby kicking, wriggling, or turning earlier since she knows what to anticipate.

The 20th week of pregnancy often represents the halfway point. According to the Mayo Clinic, preeclampsia, a disorder characterised by high blood pressure, may occur at around 20 weeks. If left untreated, the disorder may result in life-threatening consequences for both mother and child. Also present are fast weight gain and edema.

Burch encourages his patients to have a “babymoon” — a mini-vacation or weekend getaway — during the second trimester, and he suggests that the optimal time to go is around the 28th week of pregnancy. Expecting moms are often feeling very comfortable at this time, and there’s a lesser chance of miscarriage and early labour.

A study published in 2020 in the journal PLOS One indicated that for hundreds of thousands of newborns, their mother’s aircraft travel had no harmful impact on the baby’s birth weight or gestational age. However, certain health experts and airlines may prohibit flying travel beyond the 36th week of pregnancy due to the imminent possibility of delivery.

Second trimester foetal development:

Burch said that the foetus would be between 3 and 5 inches (7 to 12 cm) long throughout the second trimester. If parents choose to know the gender of their unborn child in advance, an ultrasound may disclose it between 18 and 22 weeks gestation.

By the fourth month of pregnancy, the baby has developed eyebrows, eyelashes, fingernails, and a neck, and its skin is wrinkled. According to the ACOG, during the fourth month, the arms and legs can flex, the kidneys begin to function and can create urine, and the foetus can swallow and hear.

The foetus is more active during the fifth month of pregnancy, and the mother may be able to feel its movements. The foetus also has regular sleep and waking cycles. The thin foetal skin is covered and protected by fine hair (known as lanugo) and a waxy covering (known as vernix).

By the sixth month of pregnancy, hair growth starts, the eyes begin to open, and the brain develops fast. Despite the fact that the lungs are fully developed, they are not yet functional.


In the third trimester, the mother experiences the following changes:

As the mother’s larger uterus presses on her diaphragm, a main muscle involved in breathing, throughout the third trimester, she may have difficulty breathing. According to Johns Hopkins Medicine, a woman may feel short of breath because her lungs have less space to expand. The ankles, hands, feet, and cheeks of a pregnant woman may enlarge owing to fluid retention and reduced blood circulation.

Because of the strain on her bladder, a pregnant woman will need to pee more often. As these joints develop in preparation for birth, she may also have increased backaches and hip and pelvic discomfort. According to a 2006 research published in the American Journal of Obstetrics and Gynaecology, changes in body shape may also make a pregnant person less secure on their feet and more prone to fall.

Her face may grow dark skin patches, and she may get stretch marks on her stomach, thighs, breasts, and back. Additionally, she may detect varicose veins on her legs.

According to the OWH, in the third trimester, the breasts may begin to leak colostrum, a yellow liquid, as they prepare for nursing. The infant will begin to descend in the mother’s belly.

As the due date approaches, Braxton-Hicks contractions, often known as false labour, may begin to develop. As expectant parents baby-proof their house, purchase baby supplies, and prepare the nursery for their child’s birth, a “nesting urge,” a behaviour observed by several animals, may emerge.

During the latter weeks of pregnancy, it will be more difficult to find a comfortable resting posture, which will contribute to an increase in weariness, according to Burch.

Third trimester development of the foetus:

By the seventh month of pregnancy, the baby moves and responds to light and sound, according to Burch. It can also open and shut its eyes.

During the eighth and ninth months of pregnancy, foetal weight increase is rapid. The skull stays soft and malleable so that the head may fit through the birth canal while the bones stiffen. According to ACOG, several parts of the baby’s brain are growing, and the foetus is able to hiccup.

The ninth month of pregnancy is the last stretch, and the foetus is preparing for delivery by assuming a head-down position in the mother’s pelvis. The lungs are now completely grown and able to function on their own.

Burch said that the definition of a full-term pregnancy is now 39 to 40 weeks (it used to be 37 weeks). According to the National Institutes of Health, infants delivered at term had a decreased chance of issues with breathing, eating, and temperature regulation than those born prematurely.


The time known as the “fourth trimester” starts after delivery. This may be a joyous and exciting time for most new parents, but it can also be quite difficult and stressful.

In the weeks and months after childbirth, the mother’s body continues to undergo significant changes as it rebounds from pregnancy and childbirth. Dr. Ilona T. Goldfarb, an expert in maternal health, wrote on the Harvard Health Blog that a woman must simultaneously face the physical and emotional demands of feeding and caring for a baby. During this period, Goldfarb noted, “women and their families undergo major physiological, social, and emotional changes.”

Despite the ongoing changes and difficulties that occur after childbirth, the majority of moms only contact their obstetrician once in the weeks after delivery. According to a 2018 report by the American College of Obstetricians and Gynaecologists (ACOG), more than half of pregnancy-related deaths occur after the birth of a child. Many health experts concur that this lack of attention to maternal health in the fourth trimester is concerning, especially considering that more than half of pregnancy-related deaths occur after the birth of the child.

Thankfully, a number of these specialists are exerting pressure on the healthcare profession to offer more extensive postpartum care. Goldfarb advises pregnant women to create a postpartum plan to assist in anticipating and addressing challenges when they arise. She also suggests that moms consult with their doctors to learn more about the postpartum options available to them.


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Evan Kurzyp
Evan is the founder of Fertility2Family and is passionate about fertility education & providing affordable products to help people in their fertility journey. Evan is a qualified enrolled nurse and has expertise in guiding & managing patients through their fertility journeys.

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