Week 4enparentshttps://kidshealth.org/EN/images/headers/P_PregCal_Wk4_enHD.jpgDuring this week, your baby, or embryo, has two layers of cells that will develop into organs and body parts.embryo, pregnancy, pregnancy calendar, developing fetus03/09/200108/06/201808/06/201891ea7ebc-c77e-40fb-950a-b70623964ef9https://kidshealth.org/ws/RadyChildrens/en/parents/week4.html/<h3>Your Baby's Development</h3> <p>Four weeks into your pregnancy, your baby (now an embryo) <a href="https://kidshealth.org/ws/RadyChildrens/en/parents/babyslideshow.html/"><img class="right" title="Watch Your Baby Grow" src="https://kidshealth.org/EN/images/promos/PregCal-BabyGrow-enPR.jpg" alt="Watch Your Baby Grow" /></a>consists of two layers of cells &mdash; the epiblast and the hypoblast. These eventually develop into all of your baby's organs and body parts.</p> <p>Two other structures that develop now are the amnion and the yolk sac. The amnion, filled with amniotic fluid, will surround and protect the growing embryo. The yolk sac will produce blood and help to nourish the embryo until the placenta takes over that role.</p> <h3>Your Body</h3> <p><a href="https://kidshealth.org/ws/RadyChildrens/en/parents/momandbaby-slideshow.html/"><img class="right" title="" src="https://kidshealth.org/EN/images/buttons/PregnancySlideshow-Belly-enBT-1.png" alt="Watch your belly grow!" /></a>The embryo continues to implant in your uterus, burying itself deep within the endometrium. Some women have slight cramping and spotting during this week while implantation happens. They might mistake this for a period, especially because this is around the time their monthly period was due.</p> <p><img class="left" title="Week 4" src="https://kidshealth.org/EN/images/galleries/PregCal-Week04-enGL.jpg" alt="Week 4" /></p> <p>Once implanted, the embryo starts to make a hormone called human chorionic gonadotropin (hCG), which helps to maintain the lining of the uterus. It also sends a signal to the ovary to stop releasing an egg each month, which stops your monthly periods.</p> <p>hCG is the hormone that's measured in pregnancy tests. This week, a pregnancy test probably could detect your pregnancy. hCG also causes the symptoms of pregnancy, which might start now. Tiredness, tingling or aching breasts, or nausea also can happen with premenstrual syndrome (PMS). But by the end of this week, your period won't happen. Instead, your pregnancy is under way!</p> <p> <script src="//familysurvey.org/misc/javascript/js_apps/pregnancy-calendar/kh-pregnancy-calendar-final.js" type="text/javascript"></script> </p> <div class="kh-pregnancy-calendar"> <div class="kh-pregnancy-calendar-topbar">PREGNANCY CALENDAR: <strong>A week-by-week guide</strong></div> <div class="kh-pregnancy-calendar-inner-container"> <div class="kh-pregnancy-calendar-topnav"><!-- ensure that the week value for Previous is 1 less than khPregnancyDay and that next is 1 more e.g. for week 3, Previous will be week 2 and Next will be week 4 --> <div class="kh-pregnancy-calendar-prev-active"><a href="https://kidshealth.org/ws/RadyChildrens/en/parents/week3.html/">Previous</a></div> <div class="kh-pregnancy-calendar-next-active"><a href="https://kidshealth.org/ws/RadyChildrens/en/parents/week5.html/">Next</a></div> </div> <ul> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd1" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week1.html/">1</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd2" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week2.html/">2</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd3" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week3.html/">3</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd4" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week4.html/" class="kh-pregnancy-calendar-days-active">4</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd5" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week5.html/">5</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd6" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week6.html/">6</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd7" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week7.html/">7</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd8" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week8.html/">8</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd9" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week9.html/">9</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd10" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week10.html/">10</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd11" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week11.html/">11</a></li> <li class="kh-pregnancy-calendar-days-t1"><a id="khpcd12" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week12.html/">12</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd13" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week13.html/">13</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd14" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week14.html/">14</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd15" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week15.html/">15</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd16" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week16.html/">16</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd17" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week17.html/">17</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd18" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week18.html/">18</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd19" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week19.html/">19</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd20" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week20.html/">20</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd21" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week21.html/">21</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd22" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week22.html/">22</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd23" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week23.html/">23</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd24" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week24.html/">24</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd25" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week25.html/">25</a></li> <li class="kh-pregnancy-calendar-days-t2"><a id="khpcd26" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week26.html/">26</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd27" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week27.html/">27</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd28" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week28.html/">28</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd29" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week29.html/">29</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd30" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week30.html/">30</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd31" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week31.html/">31</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd32" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week32.html/">32</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd33" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week33.html/">33</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd34" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week34.html/">34</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd35" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week35.html/">35</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd36" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week36.html/">36</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd37" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week37.html/">37</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd38" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week38.html/">38</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd39" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week39.html/">39</a></li> <li class="kh-pregnancy-calendar-days-t3"><a id="khpcd40" href="https://kidshealth.org/ws/RadyChildrens/en/parents/week40.html/">40</a></li> </ul> <div class="kh-pregnancy-calendar-trimesters"> <ul> <li class="kh-pregnancy-calendar-t1">Trimester 1</li> <li class="kh-pregnancy-calendar-t2">Trimester 2</li> <li class="kh-pregnancy-calendar-t3">Trimester 3</li> </ul> </div> </div> </div>Semana 4Semana 4https://kidshealth.org/ws/RadyChildrens/es/parents/week4-esp.html/6a678401-fa98-4413-8e6b-31e814cb4144kh:age-NAkh:clinicalDesignation-obgynkh:genre-toolkh:primaryClinicalDesignation-obgynCalendarhttps://kidshealth.org/ws/RadyChildrens/en/parents/pregnancy-center/pregnancy-calendar/5cf1d7f8-bd89-4e41-8fd9-23b431df98c0https://kidshealth.org/EN/images/promos/PregCal-BabyGrow-enPR.jpghttps://kidshealth.org/EN/images/buttons/PregnancySlideshow-Belly-enBT-1.pnghttps://kidshealth.org/EN/images/galleries/PregCal-Week04-enGL.jpg