Can blood pressure increase at the end of the 3rd trimester in healthy pregnancies?

From the Guidelines

Yes, blood pressure can increase at the end of the third trimester even in healthy pregnancies. This is a normal physiological change that typically begins around 36 weeks of gestation 1. For most healthy pregnant women, this increase is modest and stays within normal limits (below 140/90 mmHg). The rise occurs because of increased blood volume, hormonal changes, and the growing pressure of the uterus on major blood vessels.

Key Points to Consider

• Blood pressure usually declines during the first trimester of pregnancy and then slowly rises 1.
• The definition of hypertension in pregnancy is based on absolute blood pressure values (systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90 mmHg) 1.
• Women should continue with regular prenatal visits during this time so their healthcare provider can monitor blood pressure readings.
• It's essential to distinguish this normal increase from pregnancy-induced hypertension or preeclampsia, which involves blood pressure readings of 140/90 mmHg or higher after 20 weeks of pregnancy, sometimes accompanied by protein in the urine or other concerning symptoms 1.
• If a pregnant woman experiences severe headaches, visual changes, upper abdominal pain, sudden swelling, or decreased fetal movement along with elevated blood pressure, she should contact her healthcare provider immediately as these could indicate a serious condition requiring prompt medical attention.

Monitoring and Management

• Regular prenatal visits are crucial for monitoring blood pressure readings and detecting any potential issues early on 1.
• Ambulatory blood pressure monitoring may be useful for high-risk pregnant women with hypertension or those with diabetic or renal damage 1.
• Korotkoff phase V is now recommended for the measurement of diastolic blood pressure in pregnancy 1.

From the Research

Blood Pressure Increase at the End of the 3rd Trimester

• Blood pressure can increase at the end of the 3rd trimester in healthy pregnancies, as indicated by studies that analyzed blood pressure patterns in normal pregnancy, gestational hypertension, and preeclampsia 2, 3, 4.
• A study published in 2001 found that normotensive women experienced a steady decrease in blood pressure up to 20 weeks of pregnancy, followed by an increase in blood pressure up to the day of delivery, with an average 8% blood pressure increase between the middle of gestation and delivery 4.
• Another study published in 1997 found that the 24-hour mean of blood pressure for normotensive pregnant women decreased up to the 21st week of pregnancy, followed by an increase in blood pressure up to the day of delivery 3.

Factors Associated with Blood Pressure Increase

• Pregnancy-related risk factors, such as preeclampsia/eclampsia, gestational hypertension, preterm delivery, and fetal growth restriction, are associated with a significant burden of treated hypertension within 10 years of delivery 5.
• A study published in 1976 found that an elevated mean arterial pressure in the middle trimester was associated with an increased risk of stillbirth, proteinuria, hypertension, and diagnosed pre-eclampsia in the third trimester, as well as intrauterine fetal growth retardation 6.

Blood Pressure Variability During Pregnancy

• Blood pressure variability during gestation in healthy and complicated pregnancies can be useful for the early assessment of hypertensive complications in pregnancy 3.
• A study published in 2000 found that the circadian pattern of blood pressure variation for each group and trimester of gestation was established by population multiple-component analysis, and that there were highly statistically significant differences in circadian rhythm-adjusted mean between complicated and uncomplicated pregnancies in all trimesters 2.