It has been described in the late 1960s that there is a drop in blood pressure, especially Diastolic blood pressure in the second trimester at around 18 weeks. The blood pressure then subsequently rises to the pre pregnancy levels during the third trimester. The so called secondary wave of trophoblastic invasion, which produces deep modifications of the spiral arteries, and makes them insensitive to vasoconstrictors. However, recent studies by various authors show that there is no mid trimester drop; but rather, an increase as compared to the first trimester blood pressure.

Materials and Methods: We conducted a prospective study in the antenatal department of JSS Medical College & Hospital, Mysuru; over a period of one year, from July 2016 to June 2017. The blood pressures of 120 women were recorded at four different periods of gestation and compared.

Results: The systolic pressures showed a non significant but steady increase up to 32 weeks and then a significant rise when compared to the first trimester. The diastolic blood pressure and mean arterial pressure showed a non significant decrease from baseline at 16 – 20 weeks. This was  followed by a rise in both diastolic pressures and mean arterial pressure as gestation advanced.

Conclusion: Our study disproves the age old concept that there is a mid trimester fall in blood pressure. It is the first of its kind in the Indian population. 

Keywords: Systolic Blood Pressure; Diastolic Blood Pressure; Mean Arterial Pressure; Pregnancy.