The heart is one of the first organs to develop in early pregnancy, and listening to your unborn baby’s heartbeat is one of the first exciting moments as a parent. While you’re listening to those tiny thuds, it might be tempting to read a prediction of your baby’s gender into them. However, no link has been found between the sex of your baby and his heart rate.
Gender Prediction Myth
Myths abound in gender prediction, and it has been speculated that you can predict your baby's gender based on his heartbeat. According to the myth, a heart rate of more than 140 beats per minute suggests you're carrying a baby girl, while a heart rate of less than 140 beats per minute means you're likely carrying a baby boy, says the KidsHealth website.
Fetal Heart Rate
A baby's heart begins to beat approximately 22 days after conception. It starts out at a rhythm of approximately 80 beats per minute at around the fifth week of pregnancy and increases at a rate of approximately 10 beats every three days until it peaks at approximately 175 beats per minute by nine weeks gestation, according to ObGyn.net. Following this time, the heart rate begins to decline by 25 to 40 beats per minute between your 10th and 20th week of pregnancy. As you near the end of the first trimester, your baby's heart rate averages between 120 and 160 beats per minute and is audible by a hand-held Doppler instrument. Beyond the second trimester, there is another small decline in heart rate where it then stabilizes for the remainder of your pregnancy to between 100 and 160 beats per minute.
A baby's heart rate can also fluctuate depending on his activity level, explains the KidsHealth website; if you're listening in when he's busy doing back flips, his heart rate will be higher than if he were sleeping soundly in your womb.
Methods of Gender Determination
During a routine ultrasound at 18 to 20 weeks gestation, it’s often possible for the sonographer to determine the gender of your baby based upon visual examination of her genitalia. However, even the sonographer won’t confirm with 100 percent certainty that the nursery should be pink or blue. An amniocentesis, where a sample of amniotic fluid is obtained through a needle inserted through the uterus at 16 to 20 weeks, is generally performed to check for fetal abnormalities. Chorionic villus sampling, where a sample of tissue is obtained from a part of the placenta at 10 to 12 weeks, can also be used to check for abnormalities. DNA extracted during these procedures can be used to learn your baby's gender.
A newer, noninvasive testing method called cell-free DNA testing can also determine the gender of your baby after 10 weeks of pregnancy. Small fragments of fetal DNA regularly seep through the placental wall into a pregnant mother’s bloodstream. In cell-free DNA testing, a blood sample is drawn from the mother to screen for disorders and to determine paternity and gender.
- ObGyn.net: Sex, Heart Rate, and Age
- University of California San Francisco: FAQ: Cell-Free Fetal DNA Testing
- Medscape: Fetal DNA Test of Mother's Blood Reliable in Sex Detection
- Who Reproductive Library: Amniocentesis and Chorionic Villus Sampling for Prenatal Diagnosis
- American Congress of Obstetricians and Gynecologists: Nonmedical Use of Obstetric Ultrasonography
- KidsHealth: Pregnancy Myths and Tales
- The Endowment for Human Development: Prenatal Form and Function – The Making of an Earth Suit
- Inside Radiology: 18-20 Week Screening Pregnancy Ultrasound
- Photo Credit monkeybusinessimages/iStock/Getty Images
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