What Happens in the First Month of Pregnancy? – Symptoms & Tips

By BSc, MSc (embryologist) and BA, MA (fertility counselor).
Last Update: 02/22/2018

The first month of pregnancy is a special one, as it is the moment when the woman finds out that she is expecting. Even though it is not visible yet, she is able to feel the first pregnancy symptoms by the end of this month. It is at this point when a pregnancy test can provide you with an accurate result.

Pregnancy starts when the sperm meets the egg in the Fallopian tube. From this moment on, a zygote starts to form (one-cell embryo), which will grow on a daily basis until it reaches the blastocyst stage.

When the embryo becomes a blastocyst, about 7-8 days after egg fertilization, it is ready to implant to the womb of the woman. This extraordinary event is known as embryo implantation and marks the beginning of the pregnancy journey.

What happens in the first month of pregnancy?

A pregnancy is a long process that last about 40 weeks. Throughout the process, both the pregnant woman and the fetus go through a series of major changes.

Before examining the details of the first month of pregnancy week by week, it should be notes that gynecologists and all professionals from the field of assisted human reproduction start counting the weeks of pregnancy with the date of the last menstrual period (LMP).

Indeed, the reason behind this formula is due to the fact that determining the exact moment of fertilization is significantly complicated. So, for this reason, specialists consider the first day of the last menstrual period as the first day of pregnancy in 40-week pregnancies.

Nonetheless, one should not forget that some people start counting the weeks of pregnancy right after fertilization takes place, that is, just after intercourse occurs, with the subsequent creation of a new embryo.

A pregnancy typically lasts 40 weeks if we start counting from the first day of the last menstrual period (LMP) until labor. It should be reminded that, taking this into consideration, the woman is not actually pregnant during weeks 1 and 2.

So, throughout this post, we will make several references to the weeks of pregnancy by month following the criteria of specialists in obstetrics and gynecologists, which is to say, considering the first day of the last menstrual period the beginning of the first week of pregnancy.

Week 1

As mentioned above, gynecologists and assisted reproduction specialists have reached a consensus whereby the first week of pregnancy is considered to begin on the first day of the last menstrual period.

Aside from that, no other special events occur at this point. Actually, conception per se has not taken place yet. However, the female reproductive system has started to prepare itself for it:

They respond to the hormones produced by the pituitary gland, i.e. FSH and LH, and start to develop the ovarian follicles that can be found within. Also, sex hormones start to be produced, especially estrogens.
Proliferation of the endometrial lining begins one more time. It becomes thicker thanks to the action of estrogens over the uterus.

Keeping this in mind, we can consider that the first week of pregnancy is the week during which the woman experiences her last menstrual flow before getting pregnant.

Week 2

During the second week of pregnancy, two crucial events take place before embryo conception:

Follicle recruitment and selection
Out of all the primordial follicles that started to mature in the ovary, only one of them will continue its development due to its increased response to the effects of FSH.
The primordial follicle that has continued developing turns into a Graaf follicle that bursts when the LH surge occurs. As a consequence, a mature egg cells is released from the ovary.

The remaining primordial follicles stop developing and degenerate in the ovary. On the other hand, the Graaf follicle turns into what we know as corpus luteum after ovulation and starts releasing progesterone.

At this point, endometrial thickness continues increasing thanks to the action of estrogen and progesterone. It is getting ready for embryo implantation.

Ovulation may occur at the end of the 2nd week or by the beginning of the 3rd, depending on the length of your menstrual cycles. On average, ovulation takes place on day 14 in women with regular cycles. This is known as the fertile window of the woman, which is the period when the woman is most fertile and has therefore a higher chance of becoming pregnant.

Week 3

Actually, egg fertilization takes place on week 3, when the sperm cell reaches the Fallopian tube, where an egg cell ready to be fertilized is waiting.

It is at this point when the genetic material of the mother and the father fuse together to create a zygote. And that is how embryo development begins. From this day on, the zygote starts a division process during which its number of cells increases as it travels towards the uterus.

By the end of third week, the embryo reaches the blastocyst stage. Blastocyst embryos are composed of the following layers:

  • Trophoblast or trophectoderm, which will develop into a large part of the placenta.
  • Inner Cell Mass (ICM) or embryoblast, which will give raise to the organs and tissues of the fetus.

Although fertilization takes place in the Fallopian tubes on the first days of week 3, the embryo travels towards the uterus on its first days following conception in order to attach to the uterus. At the same time, the formation of the gestational sac starts too. This part of the female reproductive system will be home for the fetus during the 9 months of pregnancy.

Check out this for more information: 3 Weeks Pregnant - Symptoms & Size of the Fetus.

Week 4

Embryo implantation involves the attachment and invasion of a blastocyst embryo into the endometrial lining, that is, the inner layer that covers the inside of the uterus. Afterwards, cell specialization of the embryo begins. In other words, the development of your unborn baby starts at this point.

The first changes that occur following embryo implantation include:

Placenta development
Trophoblast cells differentiate into 2 cell layers: cytotrophoblast (inner layer) and syncytiotrophoblast (outer layer). The latter invades the wall of the uterus in order for the cytotrophoblast to develop into the placenta.
Embryonic development
The ICM differentiates into 2 cell layers as well: epiblast and hypoblast. Both layers produce what is known as bilaminar embryonic disk, which is a trilaminar embryonic disc consisting of three germ layers (ectoderm, mesoderm, and endoderm). They are responsible for the development of the embryo's tissues and organs during the 2nd month.

After implantation, the trophoblast starts releasing beta-hCG hormone, commonly known as the pregnancy hormone, as it is only secreted during pregnancy. This hormone is responsible for the earliest pregnancy symptoms, including nausea, morning sickness, abdominal bloating, stomach pain, swollen breasts, etc.

Moreover, the beta-hCG hormone is the one detected by pregnancy tests from the 4th week onwards. In short, if you get a positive pregnancy test, it means that there's presence of hCG in your system.

When a woman becomes pregnant, she does not realize that she is expecting until week 4, when a missed period leads her to consider the possibility of being pregnant. Even though a missed period is the most obvious sign of pregnancy, other symptoms such as the one mentioned above (nausea, constant urge to pee, morning sickness...) will cause her to think that pregnancy has occurred.

Read: What Are the Symptoms of Pregnancy at 4 Weeks?

Common symptoms at a glance

As one shall see, the process of conception and subsequent embryo implantation is a complex one in which many factors play a major role.

As a consequence, the beta-hCG hormone will cause a series of symptoms in the woman, but it's important to note that they may vary from woman to woman. The following are the most common ones:

  • Missed period
  • Fatigue
  • Nausea (with or without vomiting)
  • Morning sickness
  • Shortness of breath
  • Frequent urination
  • Tender, swollen, sore breasts
  • Cramping
  • Ache or stiffness in lower back
  • Food aversions or cravings
  • Slight bleeding or spotting (i.e. implantation bleeding)
  • Headaches
  • Bloating
  • Increased sensitivity to odors
  • Constipation or diarrhea
  • Mood swings
  • Dizziness or fainting
  • Increased basal body temperature

These symptoms are also commonplace during the Premenstrual Syndrome or PMS syndrome, and get often confused for pregnancy symptoms when the woman experiences a delay in her period. So, in conclusion, having all or some of these symptoms doesn't mean that you are pregnant by default.

If you have been trying to conceive, it is normal that you are now checking this list and feeling "different": moody, extremely tired, queasy, constipated, overly sensitive... In other cases, though, first pregnancy symptoms do not show up and the woman realizes after taking a pregnancy test.

How to take care & what to eat

Whether you were trying to get pregnant or you've just gotten the news that you are expecting, the basic guideline to follow from this moment on is simple: taking care of yourself and leading a healthy lifestyle.

From this moment on, the expectant mother is going to go through many physical changes, including an increase in the size of her belly and breast. Moreover, new emotions and sensations appear, which can affect the fetus as well.

For this reason, the following tips and recommendations can be significantly helpful in order to have a healthy pregnancy and promote the birth of a healthy child, with the adequate weight.


Pregnant women need to follow a balanced diet, rich in proteins, vitamins and minerals. Keep in mind that the baby is going to be feeding from you for nine months.

In particular, all pregnant women should pay special attention to the following foods and nutrients:

Folic acid
It is an essential vitamin for fetal development, since it helps prevent congenital defects of the neural tube (precursor to the central nervous system), which starts developing on the first weeks. Leafy green vegetables and pulses contain folic acid. Ideally, pregnant woman should take about 400 mg of this vitamin on a daily basis.
Dairy products
During pregnancy, taking an extra amount of calcium is necessary for the development of the baby's central nervous and musculoskeletal systems. It helps prevent gestational hypertension and preeclampsia. Skimmed or semi-skimmed milk, as well as low-fat or non-fat yogurts and semi-cured cheese, are some recommendations.
Iron-rich foods
Iron is crucial to prevent anemia. It plays a major role in hemoglobin synthesis, which is required for the transfer of oxygen to the fetus.
Fruit, vegetables, and cereals should be present on your daily eating routine.
Eating less carbs and unhealthy fats
High-calorie foods should be avoided at all costs. Pies, cakes and cupcakes are examples of high-sugar foods that could cause gestational diabetes and increase the cholesterol levels.
Products to avoid
Alcoholic drinks and coffee. They are considered toxic products that may affect fetal development and increase the risk of miscarriage.
Prevention of toxoplasmosis and listeria
Some prevention measures include washing all fruits and vegetables thoroughly, avoiding raw or undercooked meat, poultry and fish, not eating soft-boiled or raw eggs, eating hard cheeses instead of soft cheeses, etc.

At the beginning of pregnancy, getting used to this new lifestyle may be a bit overwhelming. For some women, attending support groups and sharing their doubts and experiences with other women may be highly helpful.


Giving up cigarette smoking is one of the most important things every pregnant woman should do. Nicotine may negatively impact the transfer of oxygen from the mother to the baby through the placenta, which can harm the baby by causing respiratory disorders.

If taking certain medications for certain conditions such as an urinary tract infection or cold were necessary, you should talk with your doctor previously in order to prevent them from harming the unborn baby.

As a general rule, all substances that may be detrimental for the fetus should be avoided at all costs. Exposure to toxics at the workplace or physically taxing work conditions may increase the risk of having a problem pregnancy.


High intensity training during pregnancy is totally unadvisable. So, if you practice sports that are physically demanding, you are strongly recommended to moderate the intensity. Sports such as pilates, yoga, or swimming are good options for all pregnant women.

There is no reason for you to stop exercising when pregnant unless otherwise instructed by your doctor. Just walking a few minutes every day is a good way to get exercise during pregnancy.

Of course, relaxing any time you feel the need is recommended as well. Following a healthy sleep pattern, including sticking to a sleep schedule of the same bedtime and wake up time, can help you feel way better while pregnant.

FAQs from users

How does pregnancy look like at 4 weeks?

By Zaira Salvador BSc, MSc (embryologist).

At 4 weeks, no body changes are still visible. Your baby is now well attached to your endometrial lining and has become an embryo, which looks like a tadpole (it is the size of a sesame seed). The fourth week marks the beginning of the pregnancy. You may start noticing certain pregnancy symptoms at this point.

Can I sleep on my stomach if I am one month pregnant?

By Zaira Salvador BSc, MSc (embryologist).

Yes, there's no problem with that. However, as your belly grows, you may feel uncomfortable sleeping face down. Some pregnant women are perfectly comfortable sleeping on their stomach even up until the third trimester.

How many weeks is one month of pregnancy?

By Zaira Salvador BSc, MSc (embryologist).

One month of pregnancy encompasses weeks 1, 2, 3, and 4. From week 5 until week 8, the woman is considered to be 2 months pregnant.

Can I ride roller coasters if I am one month pregnant?

By Zaira Salvador BSc, MSc (embryologist).

Although the risk is higher from the second trimester onwards, it is a risk that should be avoided. Automobile accidents are associated with pregnancy complications like placental abruption.

Suggested for you

When a woman is one month pregnant, she may notice various symptoms that are typically associated with pregnancy. However, they may unnoticed up until she takes a pregnancy test that confirms that she's indeed expecting. Get more info by clicking the following link: What Are the Earliest Symptoms of Pregnancy Before Missed Period?

As early as on the first month of pregnancy, the pregnant woman should dedicate some time to learn about prenatal care and the changes her body is going to go through. More on this story: How to Take Care of You and the Baby While Pregnant.

Our editors have made great efforts to create this content for you. By sharing this post, you are helping us to keep ourselves motivated to work even harder.



 Zaira Salvador
Zaira Salvador
BSc, MSc
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Sandra Fernández
Sandra Fernández
Fertility Counselor
Bachelor of Arts in Translation and Interpreting (English, Spanish, Catalan, German) from the University of Valencia (UV) and Heriot-Watt University, Riccarton Campus (Edinburgh, UK). Postgraduate Course in Legal Translation from the University of Valencia. Specialist in Medical Translation, with several years of experience in the field of Assisted Reproduction. More information about Sandra Fernández

Find the latest news on assisted reproduction in our channels.