If you are concerned about giving birth after your due date, talk with your doctor. He or she can help you decide what is best for you and your baby.

Your Due Date

The average length of pregnancy is 280 days, or 40 weeks from the first day of a woman's last menstrual period. It can be hard to predict the exact date. Only 5% of babies are born on their due dates.

Your due date is used as a guide for checking your pregnancy's progress and the baby's growth and age. Doctors often use more than one method to check the age of the fetus and set the due date. The size of the uterus may help assess the age of the fetus. Ultrasound also may be used to help confirm the age of a fetus.

The due date should be set as early in pregnancy as possible. Later, it becomes harder to set the due date accurately. This is one reason why early prenatal care is important.

Postterm Pregnancy

A postterm pregnancy is one that lasts 42 weeks or longer. Women who are having a baby for the first time or who have had postterm pregnancies before may give birth later than expected.

How To Estimate Your Due Date You can estimate your due date by adding 40 weeks (280 days) to the first day of your last menstrual period. This assumes that you conceived exactly 2 weeks after the first day of your last period. It also assumes that you will carry the baby for 38 weeks. Another way to calculate your due date is to: Determine the first day of your last menstrual period Add 7 days Subtract 3 months Add 1 year For example, if your last menstrual period began on April 1, 2006, you would calculate your due date as follows: April 1, 2006 + 7 days = April 8, 2006 April 8, 2006 - 3 months = January 8, 2006 January 8, 2006 + 1 year = January 8, 2007 Your estimated due date would be January 8, 2007.

A pregnancy often lasts longer than expected because the exact time when you became pregnant is not known. In some cases, the doctor might be concerned about the baby's or mother's health if a pregnancy goes beyond the due date. Labor may need to be induced (brought on with medication or other means).

Risks of Postterm Pregnancy

Health risks for the baby and mother increase if a pregnancy is prolonged. The more prolonged the pregnancy, the greater the risks. But problems occur in only a small portion of postterm pregnancies. Most women who give birth after the due date have healthy newborns.

After 42 weeks, the placenta may not work as well as it did earlier in pregnancy. Also, as the baby grows, the amount of amniotic fluid may begin to decrease. Less fluid may cause the umbilical cord to become pinched as the baby moves or as the uterus contracts. For these reasons your doctor may recommend delivery before 42 weeks of pregnancy.

If pregnancy goes past 42 weeks, a baby has an increased risk of certain problems, such as dysmaturity syndrome, macrosomia, or meconium aspiration. There also is an increased chance of cesarean birth.

Tests for Fetal Well-Being

When a baby is not born by the due date, tests can help the doctor check on the baby's health. Some tests, such as a kick count, can be done on your own at home. Others are done in the doctor's office or in the hospital. These are called electronic fetal monitoring and include nonstress test, biophysical profile, and contraction stress test.

A kick count is a record of how often you feel your baby move. Healthy babies tend to move about the same amount each day. Your doctor will explain how to do a kick count.

Electronic fetal monitoring uses two belts placed around the mother's abdomen to hold instruments that measure fetal heart rate. This method is used to perform the following tests for fetal well-being:

• Nonstress Test—The mother pushes a button each time she feels the baby move. This causes a mark to be made on a paper recording. Sometimes, a device may be put on the mother's abdomen to make a sound every few seconds. This is called acoustic stimulation. The fetal heart rate is expected to increase when the fetus moves.
• Biophysical Profile—This test combines the results of electronic fetal monitoring and an ultrasound exam. It looks at the baby's heart rate (using the nonstress test) and estimates the amount of amniotic fluid. The baby's breathing, movement, and muscle tone also may be checked.
• Contraction Stress Test—The baby's heart rate is measured when the mother's uterus contracts. The contractions are induced, and changes in the fetus's heart rate are noted.

Kick Counts If you have been asked to note your baby's kick counts, your doctor will tell you how often to do it and when to call him or her. One method is to write down how long it takes the fetus to make 10 movements. To do this, choose a time when the fetus usually is active. Often, a good time is after a meal. Each baby has its own level of activity, and most have a sleep cycle of 20–40 minutes. Alert your doctor if there is a change in the normal pattern or number of movements.

Labor Induction

If you pass your due date, your doctor may discuss inducing labor. This is when medication or other methods are used to bring on labor. Labor is induced to cause a pregnant woman's cervix to open and to prepare for vaginal birth.

Whether your labor will be induced depends on:

• Your condition and your baby's condition
• How far along your pregnancy is
• If your cervix has begun to open
• Results of tests for fetal well-being

• Ripening or dilating the cervix. Prostaglandins may be used to soften the cervix and to cause the uterus to contract for labor. These hormone-like substances can be placed in the vagina or taken by mouth.
• Rupturing the amniotic sac. Your doctor makes a small hole in the amniotic sac to release the fluid ("breaking the water"). Most women go into labor within hours of their water breaking. If labor does not occur, a different method may be used to start your labor.
• Using oxytocin. This hormone, given through an intravenous (IV) tube in your arm, causes the uterus to contract.

Finally . . .

Very few babies are born on their due dates. Most babies born after their due dates are healthy. Tests and careful monitoring during the last weeks of pregnancy and during labor can help reduce the risks for you and your baby.

If you are concerned about giving birth after your due date, talk with your doctor. He or she can help you decide what is best for you and your baby.

Glossary Amniotic Fluid: Water in the sac surrounding the fetus in the mother's uterus. Cesarean Birth: Delivery of a baby through an incision made in the mother's abdomen and uterus. Dysmaturity Syndrome: A condition in which the fetus is malnourished. He or she is born with a long and lean body, an alert look on the face, lots of hair, long fingernails, and thin wrinkled skin. Macrosomia: A condition in which a fetus grows very large. Meconium Aspiration: A condition in which the baby inhales a greenish substance that builds up in the bowels of a growing fetus. This blocks the airways and causes the baby to gasp for air. Placenta: Tissue that provides nourishment to and takes away waste from the fetus. Prostaglandins: Chemicals that are made by the body that have many effects, including causing the muscle of the uterus to contract, usually causing cramps. Ultrasound: A test in which sound waves are used to examine the fetus. Umbilical cord: A cord-like structure containing blood vessels that connects the fetus to the placenta. Uterus: A muscular organ located in the female pelvis that contains and nourishes the developing fetus during pregnancy.

This Patient Education Pamphlet was developed under the direction of the Committee on Patient Education of the American College of Obstetricians and Gynecologists. Designed as an aid to patients, it sets forth current information and opinions on subjects related to women's health. The average readability level of the series, based on the Fry formula, is grade 6–8. The Suitability Assessment of Materials (SAM) instrument rates the pamphlets as "superior." To ensure the information is current and accurate, the pamphlets are reviewed every 18 months. The information in this pamphlet does not dictate an exclusive course of treatment or procedure to be followed and should not be construed as excluding other acceptable methods of practice. Variations taking into account the needs of the individual patient, resources, and limitations unique to the institution or type of practice may be appropriate.

Copyright © April 2006 by the American College of Obstetricians and Gynecologists. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher.

ISSN 1074-8601

Requests for authorization to make photocopies should be directed to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923.

To reorder Patient Education Pamphlets in packs of 50, please call 800-762-2264 or order online at sales.acog.org.

The American College of Obstetricians and Gynecologists
409 12th Street, SW
PO Box 96920
Washington, DC 20090-6920

12345/09876