How to determine the sex of a baby in the womb

Updated June 13, 2017

There are many advantages to determining a baby's sex while it is in the womb. These include ease of selecting a name, clothing and decor in advance. In the past, many women had to rely on old wives' tales to predict a baby's sex before birth. Today, however, many medical tests are readily available and can determine whether an unborn baby is a boy or a girl with great accuracy.

When to Schedule Medical Testing

During the first trimester of pregnancy, schedule a procedure called chorionic villus sampling, or CVS. All you have to do is show up at the doctor's office; the rest is handled by trained staff. CVS involves inserting a catheter through the cervix and into the uterus in order to gather a tiny amount of the placenta. According to the Mayo Clinic, the chorionic villus contains fetal cells that contain the same DNA as the growing baby, which is why a CVS can determine the baby's sex. Schedule a CVS between the ninth and fourteenth week of pregnancy.

During the beginning of the second trimester, schedule an amniocentesis. An amniocentesis involves collecting a specimen of fluid from the amniotic sac. Trained staff insert a long needle through the belly with the guidance of ultrasound, and a small amount of fluid containing genetic material is removed. This material also contains information about the baby's sex. According to the Mayo Clinic, an amniocentesis is typically performed between week fifteen and nineteen of pregnancy.

During the second trimester of pregnancy, an abdominal ultrasound is generally scheduled as a routine test. To prepare for this test, keep the belly free from lotions, and do not empty the bladder. An abdominal ultrasound is performed by an ultrasound technician, who can determine the baby's sex by looking for the baby's external genitalia as they appear on the monitor. The Mayo Clinic reports that while an ultrasound may be performed at any time during a pregnancy, the ultrasound that determines the baby's sex is usually scheduled between weeks eighteen and twenty.

How Old Wives'Tales Work

Tie your wedding ring on the end of a string, and dangle it over the pregnant belly. Wait to see how it swings. If swings back and forth, it's a boy. If it makes a circular pattern, it's a girl.

Look in the mirror to see how the baby is being carried. A belly that is rounder up high is supposed to be a girl, while a lower pregnant belly is said to be a boy.

Gather some drain cleaner in one cup, and some of your urine in the other. Mix the two. If the drain cleaner turns brown, the baby is a girl. If it's blue, the baby is a boy. A word of caution: drain cleaner should not be handled directly by a pregnant woman, as it may be hazardous to the developing baby. If you really want to try this, ask another person do the mixing.

Time the baby's heartbeat, either with a hand-held fetal Doppler device or with a device at the doctor's office. A fast heartbeat, which is over 140 beats per minute, is said to be a boy. Lower than 140 beats per minute is supposed to be a girl.


There is no scientific proof to any of these old wives' tales, other than the fact that they have a 50 percent chance of being right or wrong. But, as Pregnancy Today states, they do make for fun baby shower games.


Both a CVS and an amniocentesis carry a small risk to the developing baby, including miscarriage. In general, they are performed to screen for genetic defects, not solely to determine the baby's sex.

Things You'll Need

  • Chorionic villus sampling test
  • Amniocentesis test
  • Abdominal ultrasound
  • Wedding ring
  • String
  • Drain cleaner
  • Mirror
  • Fetal Doppler device
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About the Author

Erica Jacques is an occupational therapist and freelance writer with more than 15 years of combined experience. Jacques has been published on and various other websites, and in "Hope Digest." She earned an occupational therapy degree from Queen Margaret University in Edinburgh, Scotland, giving her a truly global view of health and wellness.