The pregnancy is divided into three trimesters. Each trimester is a little longer than thirteen weeks. The first month of your pregnancy marks the beginning of the first trimester. If you are newly pregnant or you are trying to conceive, then you surely have many questions about what to expect. You surely want to know how your body will change. Also, you want to know what is happening inside you. But, you should not be worried about it.
You can talk with your doctor to give you a week–by–week guide, which can help you to go through your nine months of pregnancy, so you can be a more confident, smarter, and prepared mom–to–be. Also, you can read in our guide and we will help you to stop worrying about your so many questions. Each week offers information about your body and your baby, as well as helpful advice which you can use throughout your pregnancy. With this guide, you will get a peek inside the womb.
If you are a woman, then you need to know that the first month of pregnancy begins in the third week after your last menstrual period. The first few weeks of pregnancy bring them a unique set of physical and emotional changes. Also, there are several concerns during the first month, including teratogens, a higher risk of miscarriage, and ectopic pregnancy. [1,2]
How your baby develops in the first month:
After conception, the fertilized egg is traveling along the fallopian tube to the uterus, where it will implant in the uterine lining. Then, the egg divides into a bunch of cells and some of them will become the embryo and some of them eventually become the placenta, which will give you nourishment for your baby during your pregnancy.
The umbilical cord is also forming between the fetus and the placenta, which is delivering nutrients and removing the waste. The upcoming month is a time of rapid growth for your baby, as tiny limbs, bones, and intestinal organs are begging to form.
Your pregnancy week by week: Weeks 1 – 4:
Below are explained the first weeks of your pregnancy, so you should not be worried about what you should think about it.
Weeks 1 and 2:
Baby: In the first two weeks, your baby is just a glimmer in your eye. It is difficult to know when the conception has happened, so doctors calculate the due date from the beginning of your last menstrual cycle. That is right – for calculation purposes, you are pregnant before you even conceive.
Mom–to–be: At the begging of your period, about 20 eggs (called ova) occupy the fluid-filled sacs (called follicles). If you usually have your period every 28 days and then about 14 days later, you ovulate. Ovulation is a process when one of these follicles releases an egg and it travels down your fallopian tube where it awaits fertilization. This time (fourteen days after your period started and a day or so longer) is the time when you are the most fertile.
If you want to get pregnant, then this is the best time when you can do it. When the egg is fertilized, it moves into the uterus. You should not be disappointed if you do not get pregnant the first time. Depending on your age, each month, you have a 25% chance of getting pregnant, so you may need to try more than once.
Tip for weeks 1 and 2: You need to schedule a preconception visit with your gynecologist, so he or she can help to determine the risk of genetic diseases and environmental hazards, as well as learn about the necessary lifestyle changes to ensure a healthy pregnancy and baby. The most important thing is to start taking 400 micrograms or 0.4 milligrams of folic acid a day. There are some studies in which are shown that the folic acid taken a few months before conception can dramatically reduce neural tube defects, such as Spina Bifida.
Baby: This is the week when people can congratulate you on your pregnancy. If your partner’s sperm and your egg have joined successfully, then your embryo is really there, although it is very small (about the size of the head of a pin). It does not look like a fetus or baby. It is just a group of about 100 cells that are multiplying and growing rapidly. The outer layer or cell will become the placenta and the inner layer will become the embryo.
Mom–to–be: At this point, you will not notice any changes in your body. In this period, you have not even missed your period yet.
Tip for week 3: If you cannot wait to find out if you are really pregnant, then you can make a home pregnancy test. Home pregnancy tests are about as reliable as a urine test or blood test that is done in the doctor’s office and you will get the results immediately. To ensure the accuracy of this test, you need to read the directions carefully and you should be sure that all the supplies you use are clean.
Baby: In this week, your egg is fertilized and it burrows into the lining of your uterus. This is known as implantation.
Mom–to–be: In week 4, you are probably expecting your period. If it does not happen, then it may be one of the first signs that you are pregnant. Also, you may notice light spotting as the embryo implants itself in your uterus. At this period, you may not feel any different yet, but the amniotic cavity, which will be filled with fluid, and the placenta, which will bring oxygen and nutrients which can help to nourish your baby, are forming in your uterus.
Tip for week 4: You should try to eat healthily. This means that you need to choose a variety of foods from recommended food groups. Also, you need to drink at least 6 – 8 ounces of glasses of water per day. You should remember that you do not need to eat for two. You only need extra 300 calories per day while you are pregnant. Also, you should not be worried if your food intake drops in the beginning due to morning sickness. When you eat right, then your baby will get what it needs.
What is happening inside you:
The fertilized egg grows. The watertight sac forms around it and it gradually fills with fluid. This is known as an amniotic sac and it can help cushion the growing embryo. Also, the placenta develops. This is around and flat organ that transfers nutrients from you to the baby and transfers the baby’s wastes. 
The primitive face takes form with the large dark circles for eyes and the throat, mouth and lower jaw are developing. Also, blood cells are taking shape and the circulation will begin. By the end of your first month, your baby is about one–quarter inch long, which means that it is smaller than a grain of rice.
What is the gestational age:
Gestational age is the measurement for pregnancy. The first day of your last menstrual cycle is when the gestational age starts. But, the gestational age can be confusing for many people. Many people think that the pregnancy lasts for nine months. And this is true because you are pregnant for about 9 months.
But, the pregnancy is measured from the first day of your last menstrual period (which is about 3 – 4 weeks before you are actually pregnant), a full-term pregnancy usually totals about 40 weeks from the last menstrual cycle and it is roughly about ten months. Many women do not remember exactly when they started their last menstrual period and this is okay. The ultrasound is the surest way of finding out the gestational age early in the pregnancy.
Signs of pregnancy:
For many women, the first sign of pregnancy is the missed period. It is noticed that most pregnancy tests will be positive by the time you have missed your period. Also, there are other early symptoms of pregnancy, like swollen and tender breasts, nausea, mood swings, feeling bloated, feeling tired, and peeing more than usual [4,5]. Not every single woman has all of the mentioned symptoms, but it is very common to have at least one of them.
Your body changes:
You probably will not notice any changes to your body yet, but this does not mean that there is not a lot going on under the surface. At this period, it is very important to prepare your body for childbirth and pregnancy by paying attention to your overall health and nutrition. Often, this means taking a multivitamin supplement to make sure that you have all the nutrients you and your baby will need for the months ahead.
You need to talk with your doctor about the vitamins that you take, so you will be sure that you are taking the right amount of vitamins. Also, you can begin or continue with exercise, but talk with your doctors about which are safe exercises during the pregnancy.
 Sacinti KG, Kalafat E, Sukur YE, Koc A. Increased incidence of first-trimester miscarriage during the COVID-19 pandemic. Ultrasound in Obstetrics & Gynecology. 2021;57(6):1013-4.
 Li C, Zhao WH, Zhu Q, et al. Risk factors for ectopic pregnancy: a multi-center case-control study. BMC Pregnancy and Childbirth. 2015;15.
 Stanford University Medical Center. Which fertilized eggs will become healthy human fetuses? Researchers predict with 93% accuracy. Science Daily. 2010. Retrieved from www.sciencedaily.com/releases/2010/10/101003205930.htm
 Lee NM, Saha S. Nausea and vomiting of pregnancy. Gastroenterology Clinics of North America. 2011;40(2):309–vii. doi:10.1016/j.gtc.2011.03.009
 Altshuler LL, Hendrick V, Cohen LS. An update on mood and anxiety disorders during pregnancy and the postpartum period. Primary Care Companion to the Journal of Clinical Psychiatry. 2000;2(6):217–22. doi:10.4088/pcc.v02n0604