Cardiac muscle also changes its composit i on and structure over time, including a shift to a more mature helical organization well into the second trimester. But the majority of the developmental action occurs within those first nine to 10 weeks. Heartbeats are first detectable with a transvaginal ultrasound, usually after six completed weeks of pregnancy, but also sometimes during the sixth week. As Erika Werner , a maternal fetal medicine physician at Brown University and a Society for Maternal-Fetal Medicine board member , explained, the ultrasound at this stage is visual-only.
The ultrasound is picking up on the slight movement of the developing heart while it beats, as high frequency sound waves are sent out from the machine, get reflected back when they hit different kinds of fluids and tissue, and are used to form an image. The more standard abdominal ultrasound, Werner said, can be used after six to eight completed weeks. But even then, it may depend on a variety of factors.
The more tissue you have to penetrate with the sound waves, she said, the less likely the ultrasound will be able to pick up a heartbeat. Even the quality of the ultrasound machine matters. In places with poor machines, Werner noted, the flicker might not be apparent until weeks later.
The machine is handheld and also uses ultrasound waves, taking advantage of the Doppler shift. As a product manual for one such device explains, the sound is the amplified version of the difference between the transmitted and received signals.
Doppler ultrasounds, which are distinct from the handheld monitors, can also provide audio and visual confirmation of a heartbeat during pregnancy, including more detailed evaluations of fetal blood flow. The American Institute of Ultrasound in Medicine, however, discourages the use of such machines in the first trimester. To hear a true heartbeat, expecting parents can turn to a stethoscope — if they are willing to wait.
In medicine, the detection of a heartbeat is important because it signals that the embryo or fetus is alive and that the pregnancy is likelier than not to continue. The miscarriage rate, however, can be much higher in other groups. A heartbeat, then, is no guarantee of a continued or healthy pregnancy, although it is a requirement for one. A heartbeat, it should also be mentioned, does not necessarily mean that a fetus is viable, or capable of surviving outside the womb.
Older fetuses might be, but after just six weeks, no embryo is capable of living on its own, even with medical assistance. According to UpToDate, an online medical resource for physicians, many infants will live if delivered after 26 weeks of pregnancy, but almost none do if delivered before 22 completed weeks.
Viability is an important legal milestone with respect to abortion. In , the Supreme Court held in Planned Parenthood v. Greene, Greg, and Miriam Berg. Ohio General Assembly. Kentucky General Assembly. Guttmacher Institute. State Policy Updates. Schreiner, Bruce. Brown, Haywood L. Stages of Development of the Fetus. Merck Manual Consumer Edition. Nov , accessed 26 Jul Accessed 26 Jul Salomon, L. Feltman, Rachel. Anderson, Ted L. Embryology: Cardiovascular system — Blood development.
May LE et al. Aerobic exercise during pregnancy influences infant heart rate variability at one month of age. Early Human Development 90 1 Mayo Clinic. Congenital heart defects in children. Fetal ultrasound.
Tan CMJ et al. The transitional heart: From early embryonic and fetal development to neonatal life. Fetal Diagnosis and Therapy Zhang S et al. Parental alcohol consumption and the risk of congenital heart diseases in offspring: An updated systematic review and meta-analysis. European Journal of Preventative Cardiology 27 4 : Zhao L et al.
Parental smoking and the risk of congenital heart defects in offspring: An updated meta-analysis of observational studies. European Journal of Preventative Cardiology 27 Join now to personalize. Photo credit: Jonathan Dimes for BabyCenter. When does your baby develop a heartbeat? When can you see your baby's heartbeat? When can you hear your baby's heartbeat? Once you're about 20 weeks pregnant, your baby's heartbeat can be heard with a stethoscope. Some specific things you can do: Avoid smoking and secondhand smoke.
A number of studies have shown a strong link between cigarette smoke and congenital heart and other defects. Be careful with medications. Talk with your healthcare provider before trying to conceive if you're on regular medications.
Some medications — such as ACE inhibitors, the acne medication isotretinoin, lithium a psychiatric medication , and warfarin an anticoagulant increase the risk of heart defects. You and your doctor may decide together that controlling your underlying health problems with this specific medication is worth the small risk of a fetal heart defect.
However, there are often safer alternatives, so explore options with your provider. Manage any chronic health conditions. If you have diabetes before becoming pregnant, for example, take steps to control your blood sugar before and during pregnancy.
Out-of-control pre-pregnancy diabetes is one of the leading causes of congenital heart defects. Don't drink alcohol. Studies have shown that alcohol exposure during pregnancy is significantly associated with heart defects.
There's no known safe amount of alcohol during pregnancy. Get your rubella vaccination, if you need one, before becoming pregnant. When you see your doctor for a preconception visit , they can check to see if you're still immune from your childhood MMR vaccine.
Occasionally, immunity wanes and women benefit from a pre-pregnancy MMR booster. You shouldn't get the vaccination during pregnancy. Getting rubella during pregnancy can affect the development of your baby's heart. Let your doctor know about any family history of congenital heart problems. They can order special ultrasounds to monitor the development of your baby's heart. Key milestones in fetal heart development Your baby's heart develops from early in pregnancy through — and even after — birth.
You may be able to see your baby's heartbeat in an ultrasound exam. You may be able to hear your baby's heartbeat with a Doppler device. Join Our Email List. Learn more about our commitment to safety. The Franklin Institute is a C 3 nonprofit registered in the U. The Franklin Institute. How Your Heart is Formed.
A human fetus forms in a very precise order. How Fast Does it Go? Connect With Us. Facebook Instagram Twitter Youtube Linkedin.
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