During week 21 of your pregnancy, your baby continues to mature and develop, and as with other earlier weeks, week 21 is no exception when it comes to developmental strides.
These rapid changes are keeping your little one busy enough to need some sleep! Your baby is sleeping quite nicely at this point, getting about 12-14 hours of sleep per day.1
This MNT Knowledge Center feature is part of a series of articles on pregnancy. It provides a summary of each stage of pregnancy, what to expect, and insights into how your baby is developing. Take a look at the other articles in the series:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Symptoms at 21 weeks pregnant
In addition to a growing belly and weight, at this stage of your pregnancy you may continue to experience physical pregnancy symptoms.1,2
Week 21 of pregnancy may see stretch marks begin to develop around the abdomen.
These symptoms commonly include:
- Stronger nails and fuller hair
- Bloating and gas
- Increased appetite
- Fetal movement
- Varicose veins
- Bleeding gums
- Stretch marks.
Be aware that pregnancy increases the risk of urinary tract infections from week 6 to week 24, so if your symptoms are not simply from the pregnancy and you suspect an infection, speak with a health care provider about treatment.3
Your hormones at 21 weeks pregnant
Throughout your pregnancy, you will experience variations in certain hormones that contribute to many of the pregnancy symptoms you may experience. Following implantation of the fertilized egg, your body begins to secrete a hormone called human chorionic gonadotrophin (hCG) - the hormone used to detect pregnancy. This hormone is also responsible for regulating estrogen and progesterone and contributes to frequent urination.4
Initially produced by the corpus luteum, progesterone rises throughout your pregnancy and continues to do so until the birth of your baby. In early pregnancy, progesterone is responsible for increasing uterine blood flow, establishing the placenta and stimulating the growth and nutrient production of the endometrium (lining of the uterus).4
Progesterone also plays a crucial role in fetal development, preventing premature labor and lactation, as well as strengthening the pelvic wall muscles to prepare your body for labor.
In addition to progesterone, the placenta is vital in secreting important hormones during your pregnancy such as:4
- Human placental lactogen: this hormone is believed to be responsible for mammary gland growth which will be important for lactation following the birth of your baby. Additionally, it plays a role in increasing nutrient levels in your blood, which is vital to the growth and development of your baby.
- Corticotrophin-releasing hormone: this hormone is not only responsible for determining how long you will be pregnant, but also for your baby's growth and development. Later in pregnancy, the rise in both corticotrophin-releasing hormone and cortisol both completes fetal organ development and provides the mother with a surge of cortisol that has been linked with maternal attentiveness, increasing the mother-baby bond.
Another vital hormone in pregnancy is estrogen, which is responsible for fetal organ development, placental growth and function and mammary gland growth. Additionally, estrogen is needed for the regulation of other hormones produced during pregnancy.4
Because of the rise in progesterone and estrogen, you may experience some unpleasant pregnancy symptoms such as mood swings and morning sickness. Another hormone, relaxin, can cause physical symptoms such as pelvic pain, balance difficulties and constipation due to its role in relaxing maternal muscles, ligaments and joints.4
Genetic testing at 21 weeks pregnant
It is important to speak with your health care provider to determine if genetic testing and certain forms of prenatal screening are right for you.
There are three blood tests offered to women during their pregnancy to screen for a variety of genetic abnormalities including Down syndrome, Trisomy 18, and spina bifida.5
Since you are now in your second trimester, your health care provider may recommend that you are evaluated for gestational diabetes, which entails drinking a sugary liquid and checking your blood glucose levels.5
These tests include:5
- Sequential integrated screen: between weeks 10-13 and again during weeks 15-20, this screening test may be recommended to test the maternal blood for the six fetal proteins found in maternal blood circulation. This test is capable of identifying 92% of Down syndrome pregnancies. The first portion of this test is completed in combination with a nuchal translucency ultrasound - a scan showing the amount of fluid under the skin behind the baby's neck.
- Serum integrated screen: as with the sequential integrated screen, maternal blood is tested during weeks 10-13 and again during weeks 15-20 for the six fetal proteins found in maternal blood circulation. This test is capable of identifying 88% of Down syndrome pregnancies. This test is typically carried out in cases where a nuchal translucency ultrasound is unavailable.
- Quad marker screen: obtained during weeks 15-20, the quad marker screen tests maternal blood for four circulating fetal proteins. This test is capable of identifying 79% of Down syndrome pregnancies. Women who did not get the first portion of the serum and sequential tests (as above) are eligible to undergo this testing. This test is also the second test obtained during the sequential and serum screening tests.
An additional test that is performed after 15 weeks pregnancy to evaluate for certain genetic abnormalities is genetic amniocentesis. This test is typically recommended for women with abnormal prenatal screening results, prior chromosomal abnormality, family history of genetic abnormalities, a known genetic abnormality carrier status (male or female) or for women over the age of 35.5
Between weeks 17 and 20 of pregnancy, a level 1 ultrasound is completed to evaluate the baby fully for any birth defects that can be seen on ultrasound imaging. If there are any abnormal findings, it may be recommended that you undergo a level 2 scan. It is important to note that not all birth defects are visible during these ultrasounds and that a level 2 ultrasound is also recommended if any other screening tests return as abnormal.5
Baby's development at 21 weeks pregnant
At 21 weeks pregnant, there are many changes in your baby's development. Developments that are underway include:1,2
- Brain: rapid brain growth
- Bones: cartilage is converting to bone, skeleton hardens, bone marrow starts making blood cells
- Head: lanugo appearing, eyebrows forming
- Pelvis: ovaries with primitive eggs and formed uterus in females, testicular descent in males
- Limbs: arms and legs are proportionate
- Other: fetal movement present, taste buds develop, swallowing amniotic fluid.
Lifestyle changes at 21 weeks pregnant
At week 21 of pregnancy, your baby can swallow amniotic fluid and taste it with newly developing taste buds.
As with earlier weeks, you will soon find out that there are many lifestyle modifications which need to be made during pregnancy and even after delivery.
During pregnancy, you will need to take care of yourself and your developing baby. Be sure not to drink alcohol or smoke during pregnancy, and avoid all other toxic substances such as drugs during this time.
Be sure to discuss all medications you are taking with your health care provider to ensure that you should continue use during your pregnancy.6
To nourish yourself and your baby, make sure you eat a healthy diet and take a good prenatal vitamin.
Another way to maintain your health during pregnancy is to get regular exercise. Speak with your health care provider about your current or desired exercise regimen to make sure it is safe.6
While it is safe to eat fish during pregnancy, it is recommended that you limit your intake to 8-12 oz. of fish and shellfish per week.3,7,8
Some examples of fish that are safe to consume during pregnancy include shrimp, salmon, canned light tuna (note: mercury varies can to can), pollock, cod, catfish and anchovies.3,8 If you plan on eating albacore tuna and tuna steak, it is recommended that you limit consuming this fish to 6 oz. per week.7,8
Avoid eating shark, swordfish, tilefish and king mackerel while pregnant, as they contain high levels of mercury which can be harmful to your baby's brain and nervous system.7 If eating fish from a non-commercial source - a fish you or your family caught, for example - be sure to check with the local health authorities that the waters in which it was caught are safe.7
Always make sure your food is fully cooked and not raw or undercooked. Also avoid uncooked smoked or pickled fish.7 Additionally, it is important to avoid unpasteurized soft cheese, refrigerated pâté, raw or undercooked meat and poultry, cold cut deli meat, foods containing raw eggs (Caesar dressing, etc.) and unpasteurized juice, milk and eggnog.7
Need a boost? Caffeine is OK during pregnancy but should be consumed in moderation. Try to keep your caffeine consumption from all sources at or below 300 milligrams daily.7
Baby's size at 21 weeks pregnant
At week 21 of pregnancy, your baby will measure the same length as a long banana.
Your baby is now the size of a banana, measuring nearly 7 inches long and weighing nearly 11 oz.1
Despite your baby's increasing size, there is still plenty of room in the womb at this stage for them to move around.
If you have questions regarding your pregnancy, be sure to contact your health care provider.
Call your doctor if you are experiencing symptoms of an ectopic pregnancy or miscarriage such as vaginal bleeding or passage of tissue, leaking vaginal fluid, feeling faint or dizzy, low blood pressure, rectal pressure, shoulder pain and severe pelvic pain or cramping.
Recent developments on pregnancy from MNT news
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