Preventive strategies of pre-eclampsia
I read with interest the recent review by Professor Shennan (1). An
excellent account of recent developments in obstetrics is provided.
However, I would like to make certain comments on the preventive
strategies of pre-eclampsia.
The importance of low-dose aspirin has already been highlighted (1).
However, the exact period when it should be started is not clear. It is
almost certain that it is of no use when taken in the inter-pregnancy
interval. However, it should be started in early second trimester in women
with past history of pre-eclampsia or among those detected to be at high-
risk by transvaginal Doppler ultrasound study of the uterine arteries at
12 to 14 weeks of gestation (2). Another interesting aspect to note is the
time-dependent effects of aspirin on lowering of blood pressure. Aspirin
has been shown to have the maximum effect on lowering of blood pressure
when taken before bedtime or eight hours after awakening as compared to
just after awakening (3).
The role of Vitamins C and E has also been highlighted (1). The
effect is believed to be due to their antioxidant properties. While on
this point, we should also note the effects of smoking. Maternal smoking
was found to be protective against pre-eclampsia in nulliparous women (4).
In another study, a significantly increased risk of pregnancy-induced
hypertension was found among women who never smoked (5). The protective
effect of smoking could be due to its antioxidant properties. However,
smoking may adversely affect maternal and foetal outcomes due to its other
ill effects and hence cannot be recommended.
Role of calcium has not been discussed in the present review. Calcium
supplementation is beneficial for women at high risk of gestational
hypertension and in communities with low dietary calcium intake (6).
Pre-eclampsia is more common in first pregnancies. The risk is
reduced by half in subsequent pregnancies. However, this reduction in risk
of pre-eclampsia is not seen in women who conceive with new partners (7).
An immune-based etiologic mechanism is proposed, whereby prolonged
exposure to foetal antigens from a previous pregnancy protects against pre
-eclampsia in a subsequent pregnancy with the same father. This should be
a strong incentive for maintaining long-term relationship with single
In conclusion, role of calcium and subsequent conception with same
partners in prevention of pre-eclampsia need to be highlighted. The timing
of aspirin administration is also important and could explain the lack of
efficacy shown in some trials.
1.Shennan AH. Recent developments in obstetrics. BMJ. 2003; 327: 604-
2.Vainio M, Kujansuu E, Iso-Mustajarvi M, Maenpaa J. Low dose
acetylsalicylic acid in prevention of pregnancy-induced hypertension and
intrauterine growth retardation in women with bilateral uterine artery
notches. BJOG. 2002; 109: 161-7.
3.Hermida RC, Ayala DE, Iglesias M. Administration time-dependent
influence of aspirin on blood pressure in pregnant women. Hypertension.
2003; 41: 651-6.
4.Xiong X, Wang FL, Davidge ST, Demianczuk NN, Mayes DC, Olson DM, et
al. Maternal smoking and preeclampsia. J Reprod Med. 2000; 45: 727-32.
5.Morris CD, Jacobson SL, Anand R, Ewell MG, Hauth JC, Curet LB, et
al. Nutrient intake and hypertensive disorders of pregnancy: Evidence from
a large prospective cohort. Am J Obstet Gynecol. 2001; 184: 643-51.
6.Atallah AN, Hofmeyr GJ, Duley L. Calcium supplementation during
pregnancy for preventing hypertensive disorders and related problems.
Cochrane Database Syst Rev. 2002;(1): CD001059.
7.Saftlas AF, Levine RJ, Klebanoff MA, Martz KL, Ewell MG, Morris CD,
et al. Abortion, changed paternity, and risk of preeclampsia in
nulliparous women. Am J Epidemiol. 2003; 157: 1108-14.
Competing interests: No competing interests