10. CONDITION: Antepartum Management of Prolonged Pregnancy
A. Introduction:
The accurate determination of the time of conception is extremely important in reducing the false diagnosis of post-term pregnancy and in precisely ascertaining the point at which a pregnancy becomes high risk. The expected date of confinement (EDC) is most reliably and accurately determined early in pregnancy. Consistency between historical and physical data is important in establishing the reliability of dating.
B. Definitions:
(1) Prolonged Pregnancy is pregnancy that lasts greater than 287 days (41 completed weeks) from the first day of the last menstrual period.
(2) Post-term Pregnancy is a pregnancy that lasts greater than 294 days (42 completed weeks) from the first day of the last menstrual period.
(3) Criteria for confirming gestational age should include 2 of the following in addition to a complete menstrual history.
(a) Fetal heart tones have been documented by 20 weeks gestation by non-electronic fetoscope or by 13 weeks gestation by electronic fetoscope;
(b) Uterine size has been established by pelvic examination prior to 16 weeks of gestation;
(c) A positive serum or urine human chorionic gonadotropin (hCG) pregnancy test was done and recorded 6 weeks after the last normal menstrual period;
(d) Ultrasound:
(1) Measurement based on the "crown-rump length" obtained between 6 and 11 weeks of gestation, or
(2) Measurement based on the "biparietal diameter" obtained between 12 and 20 weeks of gestation.
(4) Gestational age cannot be accurately determined by using the criteria in (3) above if the patient presents at 22 weeks gestation or later.
C. Action:
(1) At 41 weeks gestation (plus or minus 2 days), the patient should have a nonstress test (NST). If reactive, the practitioner may elect to continue to follow the pregnancy.
(2) Between 41-42 weeks gestation, the patient should have an ultrasound to evaluate adequacy of amniotic fluid. Results of the ultrasound need to be available within 24 hours. If determined to be adequate, the practitioner may elect to continue to follow the pregnancy.
(3) Between 42-43 weeks gestation, the patient should have two (2) nonstress tests (NST) performed. The first should be performed approximately one (1) week after the nonstress test at 41 weeks gestation and the second should be performed three to four (3-4) days after the first. If reactive, the practitioner may elect to continue to follow the pregnancy.
(4) Ultrasound evaluation of the adequacy of amniotic fluid should be completed at weekly intervals after the initial ultrasound completed at 41-42 weeks. Results of the ultrasound need to be available within 24 hours. If determined to be adequate, the practitioner may elect to continue to follow the pregnancy.
(5) If possible, ultrasound exams performed at 41 weeks gestation and beyond should contain a report on the estimated fetal weight.
(6) At 43 weeks gestation the patient should be delivered.
(7) Contraction stress tests (CST) can be substituted for nonstress tests (NST) in the above actions.
(8) Biophysical profiles can be substituted for ultrasound exams in the above actions.
D. Contraindications to the Proceeding Protocol. Patients with any of the following diagnoses/problems should have individual treatment plans:
1. Gestational Diabetes.
2. Hypertension in Pregnancy.
3. Macrosomic Infant.
4. Intrauterine Growth Retardation.
5. Previous History of Fetal Demise; or,
6. Fetus with uncertain gestational age and/or prenatal care starting at or after 22 weeks gestation.
References:
(1) ACOG Technical Bulletin, Number 130, July 1989, pp. 1-4.
(2) Clinical Standards for the Obstetrical Services of the Harvard Medical Institutions, Dec. 1, 1988.
(3) Guidelines for Perinatal Care, 2nd ed., (Evanston, Illinois: American Academy of Pediatrics/American College of Obstetricians and Gynecologists, 1988). As adapted by the Advisory Committee on Obstetrics and Gynecology Practice Parameters and Protocols.
(4) Eastern Maine Medical Center Family Practice Residency Program Protocol for the Prevention and Management of Postdates Pregnancy, January 1990.
EFFECTIVE DATE: July 28, 1991
AMENDED: February 22, 1995
02 DEPARTMENT OF PROFESSIONAL AND FINANCIAL REGULATION
373 BOARD OF LICENSURE IN MEDICINE
