Dr. Marjorie Greenfield
Specializing in pregnancy and birth.
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 Ask Dr. Greenfield
Due Date Confusion Due to Baby's Size | | | QUESTION | | | Dear Dr. Greenfield,
I am expecting a child and the due date is in question. December 7th was my original due date before it was changed to November 27th. Now the November date is in question because I am measuring at about two weeks bigger than I should be. Today I saw a doctor who said that she was not going to change my due date--I am going to have a very large baby and am only 29 weeks along. But the baby's measurements have him at almost 32 weeks (three pounds, six ounces). She also said that I will most likely need to have a cesarean. Is it possible that I am due sooner then she seems to think and that the baby is the "correct" size?— Stefinie4 in Ballston Spa, New York | | | ANSWER |
October 11, 2001 | | | Dear Stefinie4,
Estimating the due date can be confusing, especially when there are discrepancies between the different parameters that we use. In general, a known certain last period in a mother-to-be with regular cycles is considered the most reliable measure. But if ultrasound done early in pregnancy is inconsistent with that date, the sonogram is considered more definitive. In early pregnancy, ultrasound is accurate, give or take about a week. Later in pregnancy, the due date calculated by ultrasound is less accurate, because third trimester babies are different sizes, even at the same gestational age.
Even though it sounds like your baby may be big, and you may have a greater chance of needing a cesarean, most doctors will recommend that you try for a vaginal birth unless they think the baby is huge--over ten pounds. Even then, there are pros and cons to just scheduling a cesarean. Your doctor will make a recommendation to you about the mode of birth when you get closer to term, taking into account the size of your pelvis, the size of the baby and other factors that may play a role.
The bottom line is--the earliest scan is the most accurate, and the later scans are probably indicative of the size your baby is growing to, not his gestation. Take care--and have a happy and healthy big baby, whichever way you give birth!— by Marjorie Greenfield, M.D. |
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