Twin fetal weight chart: Estimated growth week by week

A recent study examined how twins grow in the second half of pregnancy. Have a look at twin fetal weight charts week by week.

By Kate Phillipa Clark

The ultrasound-based twin fetal weight charts below are based on a twin study from 2015.  It was published in the American Journal of Obstetrics & Gynecology and adds significantly to the field of fetal growth assessment in twins. A total of 642 twin fetuses – with a total of 3078 ultrasound observations – were included in the study. Researchers developed a twin fetal weight chart for dichorionic twins in the second half of pregnancy. They also developed a twin fetal weight chart for monochorionic twins.

What does the study show?

The study showed, as expected, that monochorionic twins were consistently smaller than dichorionic twins. It also reaffirmed that twins generally are smaller than singletons. It showed that twin fetal growth accelerates in the second trimester and continues in a linear pattern in the third trimester until term. This reduction in fetal growth is significant, particularly in the third trimester, compared with singletons. It concluded that dichorionic twins deviates from singleton reference charts at approximately 32 weeks. Monochorionic twins deviates at 28 weeks. These deviations are one of the reasons why a singleton fetal weight chart shouldn’t be applied to twins. The normal declaration of growth in twins can seem like an issue, even if it isn’t.

How do I read a twin fetal weight chart?

Fetal growth is better monitored with a doctor. A twin fetal weight chart shouldn’t be used in isolation without all the other important pregnancy monitoring visits. Also be aware that there’s nothing wrong with your children being below the median weight. The median weight is the value for which 50 percent of the fetuses are bigger, and 50 percent are smaller. It  separates the higher half from the lower half. To give you a better sense of how small or big your babies are, we’ve also included the 10th and 90th percentile.

What’s the 10th and 90th percentile?

If your babies estimated weights are equal to or less than the weight indicated as the 10th percentile, it means that your babies are among the smallest 10 percent. If your babies estimated weights are equal to or above the weight indicated as the 90th percentile, your babies are among the biggest 10 percent.  If you’re worried about the growth of your babies, it’s important that you consult your doctor or healthcare provider. Growth of twins is an important characteristic to be monitored along with other variables like The Fetal Non-Stress test (NST monitoring).


Estimated fetal weight in dichorionic twins

Weeks10th percentileMedian fetal weight 90th percentile
22434 grams / 15oz522 grams / 1lbs, 2oz628 grams / 1lbs, 6oz
23508 grams / 1lbs, 1oz
609 grams / 1lbs, 5oz731 grams / 1lbs, 9oz
24587 grams / 1lbs, 4oz702 grams / 1lbs, 8oz840 grams / 1lbs, 13oz
25687 grams / 1lbs, 8oz820 grams / 1lbs, 12oz979 grams /2lbs, 2oz
26790 grams / 1lbs, 11oz941 grams / 2lbs, 1oz1120 grams / 2lbs, 7oz
27894 grams / 1lbs, 15oz1063 grams / 2lbs, 5oz1263 grams / 2lbs, 12oz
281020 grams / 2lbs, 3oz1210 grams / 2lbs, 10oz1435 grams / 3lbs, 2oz
291154 grams / 2lbs, 8oz1367 grams / 3lbs1620 grams / 3lbs, 9oz
301299 grams / 2lbs, 13oz1537 grams / 3lbs, 6oz1819 grams / 4 lbs
311463 grams / 3lbs, 3oz1730 grams / 3lbs, 13oz2046 grams / 4lbs, 8oz
321631 grams / 3lbs, 9oz1929 grams / 4lbs, 4oz2281 grams / 5 lbs
331785 grams / 3lbs, 14oz2110 grams / 4lbs, 10oz2496 grams / 5lbs, 8oz
341944 grams / 4lbs, 4oz2300 grams / 5lbs, 1oz2721 grams / 6 lbs
352100 grams / 4lbs, 10oz2486 grams / 5lbs, 7oz2943 grams / 6lbs, 7oz
362271 grams / 5lbs2691 grams / 5lbs, 14oz3190 grams / 7 lbs
372417 grams / 5lbs, 5oz2869 grams / 6lbs, 5oz3404 grams / 7lbs, 8oz

Estimated fetal weight in monochorionic twins

Weeks10th percentileMedian fetal weight 90th percentile
22437 grams / 15oz508 grams / 1lbs, 1oz590 grams / 1lbs, 4oz
23506 grams / 1lbs, 1oz589 grams / 1lbs, 4oz685 grams / 1lbs, 8oz
24591 grams / 1lbs, 4oz689 grams / 1lbs, 8oz803 grams / 1lbs, 12oz
25681 grams / 1lbs, 8oz795 grams / 1lbs, 12oz929 grams / 2lbs
26776 grams / 1lbs, 11oz908 grams / 2 lbs1062 grams / 2lbs, 5oz
27866 grams / 1lbs, 14oz1015 grams / 2lbs, 3oz1190 grams / 2lbs, 9oz
28989 grams / 2lbs, 2oz1163 grams / 2lbs, 9oz1367 grams / 3lbs
291097 grams / 2lbs, 6oz1293 grams / 2lbs, 13oz1524 grams / 3lbs, 5oz
301251 grams / 2lbs, 12oz1479 grams / 3lbs, 4oz1749 grams / 3lbs, 13oz
311385 grams / 3lbs1642 grams / 3lbs, 9oz1947 grams / 4lbs, 4oz
321531 grams / 3lbs, 6oz1821 grams / 4lbs2166 grams / 4lbs, 12oz
331687 grams / 3lbs, 11oz2014 grams / 4lbs, 7oz2404 grams / 5lbs, 4oz
341823 grams / 4lbs2183 grams / 4lbs, 13oz2614 grams / 5lbs, 12oz
351985 grams / 4lbs, 6oz2386 grams / 5lbs, 4oz2869 grams / 6lbs, 5oz
362123 grams / 4lbs, 10oz2561 grams / 5lbs, 10oz3089 grams / 6lbs, 12oz
372230 grams / 4lbs, 14oz2697 grams / 5lbs, 15oz3261 grams / 7lbs, 3oz
About the Author

Kate Phillipa Clark

Kate Phillipa Clark has a bachelor in Journalism and an Executive Master in Corporate Communication. She is an identical twin and so is her father.


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