Perinatology, also known as maternal-fetal medicine, is a specialized branch of medicine dedicated to managing pregnancies that are considered high-risk. This field focuses on addressing complex health conditions that can affect either the mother or the developing baby, ensuring the safest possible outcomes for both. A central concept in pregnancy management is the estimated due date (EDD), which is the projected date when childbirth is expected to occur. This date serves as an estimate, providing a general timeframe rather than a precise deadline for delivery.
How an Initial Due Date is Established
The initial estimated due date is commonly determined through a combination of methods, with increasing reliance on early ultrasound measurements for accuracy. Traditionally, a due date was calculated using the first day of the last menstrual period (LMP) through a method known as Naegele’s rule. This calculation adds 280 days, or 40 weeks, to the LMP.
While the LMP method provides a preliminary estimate, a first-trimester ultrasound is now considered the most reliable approach for establishing the EDD. This ultrasound, performed between 7 and 13 weeks of gestation, involves measuring the crown-rump length (CRL). The CRL is the measurement from the top of the head to the bottom of the buttocks, and it correlates precisely with gestational age during this early period. This early CRL measurement provides the most accurate estimated due date, which is then maintained throughout the pregnancy, even if later scans suggest different growth patterns.
The Perinatologist’s Role in Due Date Management
A perinatologist does not alter the estimated due date established by an early first-trimester ultrasound. Instead, they utilize this precise date as a benchmark for monitoring fetal development in high-risk pregnancies. Their role involves detailed assessments to track the baby’s growth and well-being, ensuring that development progresses as expected.
Perinatologists use subsequent detailed ultrasounds (growth scans) to assess various fetal biometrics. These measurements include the fetal head circumference, abdominal circumference, and femur length. These measurements are then compared against established growth percentiles corresponding to the gestational age derived from the initial EDD. This analysis helps confirm the baby is developing appropriately and allows the perinatologist to identify deviations or concerns early, enabling proactive management.
Medical Reasons for a Planned Early Delivery
In high-risk pregnancies, there is a clear distinction between the estimated due date, which marks the 40-week gestation point, and the actual planned delivery date. A perinatologist may recommend a scheduled induction of labor or a Cesarean section well before the estimated due date to safeguard the health and safety of either the mother or the baby. This approach is based on assessment of medical conditions that could pose risks if the pregnancy continued to term.
Conditions such as severe preeclampsia, a hypertensive disorder, often necessitate early delivery to prevent eclampsia or other maternal complications. Intrauterine growth restriction (IUGR), where the fetus does not grow as expected, may also prompt early delivery to prevent compromise to the baby’s health. Placental issues, including placenta previa where the placenta covers the cervix, or placental abruption where it separates too early, also frequently require a planned early delivery for maternal and fetal safety. Poorly controlled maternal health conditions, such as severe diabetes or chronic hypertension, can increase risks to the baby and mother, leading to an earlier, controlled delivery for optimal outcomes.