Chronic hypertension in pregnancy refers to high blood pressure that is present before pregnancy or is diagnosed before the 20th week of gestation. In Nigerian clinical practice, midwives often encounter women who already manage known high blood pressure, as well as those who discover their elevated readings during their first booking visit in the antenatal clinic. The standard diagnostic threshold is a blood pressure reading of 140/90 mmHg or higher, measured on two separate occasions.
It is distinct from gestational hypertension, which develops after 20 weeks without protein in the urine, and from preeclampsia, which brings multisystem involvement. Identifying the exact timeline of the high blood pressure is vital because it changes how the midwife plans the antenatal care pathway. A thorough history taking during the booking visit focuses on how long the woman has lived with high blood pressure and whether she was taking regular antihypertensive medications before conception.
Most pregnant women presenting with chronic hypertension have primary or essential hypertension, where no single underlying medical cause can be found, though family history and lifestyle factors play a part. In a smaller number of cases, secondary hypertension occurs due to an identifiable condition, most commonly chronic kidney disease, renal artery stenosis, or endocrine disorders like Cushing's syndrome.
Long-standing high blood pressure causes gradual damage to the inner lining of blood vessels, known as the endothelium. This vascular stiffness reduces blood flow to vital organs. When a woman with this baseline vascular damage becomes pregnant, her placental spiral arteries may fail to remodel properly, increasing her vulnerability to further complications as the pregnancy progresses.
Chronic hypertension carries substantial risks for both the mother and the developing fetus throughout the antenatal and postpartum periods.
The initial booking visit sets the foundation for managing chronic hypertension in pregnancy. Midwives must perform a comprehensive assessment to grade the severity of the hypertension and check for target organ damage that existed before conception.
Essential baseline investigations include:
Managing chronic hypertension balances the need to lower maternal blood pressure with the need to maintain adequate blood flow to the placenta. Midwives educate women on home blood pressure monitoring and recognizing danger signs.
Antihypertensive medication is typically continued if the woman was already taking it, provided the drug is safe in pregnancy. Methyldopa, labetalol, and nifedipine are standard choices in many Nigerian health facilities. ACE inhibitors and angiotensin receptor blockers are strictly avoided because they cause severe fetal renal abnormalities and malformations.
Clinic visits are scheduled more frequently than in normal pregnancies. Midwives check blood pressure, test urine for protein at every visit, and monitor fetal well-being through clinical palpation and serial scans.
Superimposed preeclampsia occurs when a pregnant woman with chronic hypertension develops new signs of preeclampsia, such as sudden worsening of blood pressure, new protein in the urine, or symptoms of end-organ dysfunction. This dangerous complication can develop rapidly and requires prompt recognition by the midwifery team.
Clues that point toward superimposed preeclampsia include a sudden spike in blood pressure that was previously well-controlled, new-onset persistent headaches, visual disturbances like blurring or flashing lights, and upper abdominal or epigastric pain. Midwives must remain highly vigilant during every antenatal contact, routinely checking urine protein and asking about these warning signs.
Planning the time and mode of delivery is a crucial part of managing chronic hypertension. For women with well-controlled chronic hypertension and no additional complications, delivery is usually planned between 38 and 39 weeks of gestation. If complications like superimposed preeclampsia or fetal growth restriction develop, delivery may be brought forward.
During labor, continuous blood pressure monitoring is essential. Midwives administer prescribed antihypertensive drugs if readings spike to severe ranges, aiming to prevent maternal stroke. Vaginal delivery is entirely appropriate unless obstetric indications require a cesarean section. Careful monitoring continues into the postpartum period, as blood pressure can fluctuate significantly in the days following childbirth.