Why would twins heart rate drop from 160 to 140 at 20 weeks gestation?

Not uncommon. Variations of 10-20 beats per minute is not uncommon and even different positions of the mother may cause the fetal heart rate to change. Food, medications, and substances the mother takes in can also affect the growing baby and cause fluctuations in the heart rate, for example caffeine may stimulate the baby heart rate to increase, etc. Best wishes and congratulations.

Related Questions

20 weeks pregnant and lately my blood pressure drops to 95-98/60-65. Isthis bad for baby? Resting Heart rate 80-100bpm most days. Worried about baby

BP in pregnancy. Blood pressure usually decreases in second trimester and is usually at the lowest from 24 to 26 weeks. At your range of BP and pulse that appears normal so long as all your cardiovascular evaluation is normal.
Please when in doubt, kindly discuss with your doctor for further reassurance.
Good luck. Read more...

Is it dangerous for me to get my heart rate over 140 beats per minute during pregnancy?

Not necessarily. Heart may increase during pregnancy. I will recommend to see your pcp or a cardiologist to make sure that you have physiological tachycardia and not cardiac arrythmias, which is a possibility during pregnancy. Read more...

Is it dangerous for me to get my heart rate over 140 beats per minute during pregnancy?

Pregnancy findings. The heart rate goes up through pregnancy, at rest and during exercise. Some arrhythmias can flare up during pregnancy as well (including those that are not dangerous). A resting heart rate of 140 is fast but not usually dangerous. But you should have your doctor do an ekg and/or heart monitor to ensure you are not having a rhythm abnormality that needs treatment. Read more...