Hypotension in Threatened Preterm Labour Treating with Initial Loading Dose of 30 mg versus 40 mg Nifedipine

Preterm birth significantly contributes to infant morbidities and neurological disability. It has been hope that tocolytic treatment would reduce the consequences of preterm birth by prolonging pregnancy Calcium channel blockers (CCB) have been used to prevent preterm labor over 20 years. Nifedipine is the first CCB used for tocolytics therapy by 1980 Although nifedipine has significantly lower of maternal and fetal side-effects than alternatives, but the major concern is about vasodilating properties which can induce maternal tachycardia, headache, nausea, hot flush, palpitation and especially severe hypotension Suchaya 2010 study in 157 Thai women 17% of cases experienced hypotension within 60 min after receiving nifedipine. Of these there was no severe hypotension. But if the pregnant women had lower baseline, profound shock can be occurred (Before using nifedipine, the mean systolic and diastolic blood pressures were 109.4 +/- 10.4 and 72.5 +/- 7.9 mmHg the mean decrease of systolic and diastolic blood pressure in severe hypotension was 16.3 and 14.5 mmHg) The incidence of profound hypotension(BP<90/60 mmHg) at first 60 minutes is 3.8% From previous study show that there was same effectiveness of using oral nifedipine 30 mg between 40 mg loading in the first hour for tocolysis .In Suchaya 2010 trial was study in Thai pregnant woman show incidence of hypotension was 17% when treated preterm labour with initial loading dose 40 mg . We aim that decreasing the incidence of hypotension could be reached by lowering the initial nifedipine loading dose