It is quite common to have low blood pressure while pregnant due to the numerous body changes occurring at this period. Most women begin to experience a drop in their BP early in the first trimester with the middle of the second trimester often marking the point when the blood pressure is lowest . It does not generally lead to any adverse outcome, but severe cases may be dangerous for both the mother and baby.
The systolic (the top number) blood pressure reading ranging around 120 and the diastolic (the bottom number) pressure ranging around 80 is normal in a healthy individual. You are considered to have low blood pressure if either one of the readings is lower than normal . In most pregnant women, the systolic reading drops by 5-10 mmHg while the diastolic pressure drops about 10-15 mmHg. However, these readings may vary depending on your medical history and overall health .
|Severity Level ||Systolic Pressure||Diastolic Pressure|
|Borderline low BP||90 mmHg||60 mmHg|
|Low BP (mild)||60 mmHg||40 mmHg|
|Extremely low BP||50 mmHg||33 mmHg|
Although commonly occurring in pregnant women, low BP is not a sign of pregnancy as it often remains asymptomatic in early first trimester.
The rapid expansion in your blood volume for supplying enough oxygen and nutrients to the baby dilates the blood vessels, causing your blood pressure to drop . This is the most common cause of hypotension in pregnancy while other possible causes include carrying twins, a history of low BP or having underlying health issues like dehydration, anemia, endocrine problems and certain heart disorders . Other risk factors such as folic acid and/or vitamin B12 deficiency or being on a prolonged bed rest  may also be responsible. Administration of epidural often leads to sudden drop in blood pressure during labor .
It is usually diagnosed during your regular prenatal checkup as your doctor routinely checks your BP for any abnormalities. Additional tests may be ordered to detect the exact causes:
Majority of cases do not need any treatment as the blood pressure starts to go up automatically during the third trimester, becoming normal after childbirth . Those refusing to resolve on their own may be managed at home with certain dietary and other health measures. Here are some tips for raising your BP levels and avoiding the symptoms:
Drugs and medications are not used unless there are serious symptoms or significant threat of complications for the mother or baby .
Watch out for the following symptoms as they may indicate serious underlying problems when occurring along with low BP:
Extremely low blood pressure may increase the risks of key organ damage in the mother . In some rare cases, it may also be associated with complications like ectopic pregnancy .
There is a lack of adequate research regarding the effects of maternal low BP on the baby. But, some studies show it to increase the risks of low birth weight and learning difficulties in the child as well as fetal death due to inadequate blood flow .
The ICD-9 codes used for hypotension are 796.3 and 458  while its ICD-10 code is I95 .