Smoking during pregnancy. Its effect on maternal metabolism and fetoplacental function.

The effects of smoking during pregnancy on maternal body composition and the fetoplacental unit were investigated serially in well-matched groups of 29 normal, healthy primigravid smokers and 31 nonsmokers. The babies of smokers were lighter by an average of 138 g, and there was a greater proportion of small-for-dates infants among smokers compared with nonsmokers. There was a failure in expansion of mean plasma volume and total body water in patients who smoked throughout pregnancy compared with nonsmokers. No differences were demonstrated in serum protein, intravascular protein mass, serum albumin, intravascular albumin mass, serum electrolytes, serum osmolality, urinary estriol excretion, fetal biparietal diameter, or weekly growth rate between the 2 groups. The concentration of serum heat-stable alkaline phosphatase at 34 and 38 weeks' gestation, during the second stage of labor, and in the early puerperium was significantly higher in smokers. It is postulated that smoking unfavorably alters maternal body composition which is manifested in poor overall performance with the consequent production of smaller infants. The effects of tobacco smoke on the fetus may possibly be mediated via the placenta.

Amniotic fluid testosterone in the prenatal determination of fetal sex.

In the field of genetics, a rapid and accurate test for the prenatal determination of fetal sex, especially in cases of sex-linked disorders, is desirable. Amniotic fluid testosterone was measured by the radioimmunoassay technique in 37 samples obtained at saline abortion between 16 and 19 weeks' gestation. Final confirmation of fetal sex was obtained from fetal gonadal histology. In pregnancies with male fetuses, the mean amniotic fluid testosterone value of 27.6 ng. per 100 ml. was significantly higher (p less than 0.001) than the mean value of 9.6 ng. per 100 ml. found in pregnancies with female fetuses. The range for pregnancies with male fetuses was 15.5 to 41.3 ng. per 100 ml. and for those with female fetuses 5.7 to 15.1 ng. per 100 ml. With a coefficient of variation of 5 to 8% considered for the method of assay, there was an area of potential overlap from 12 to 18 ng. per 100 ml., giving a predictive error of approximately 16%. For patients in whom the results are clearly outside the area of overlap, this test is of value as a preliminary screen in the prenatal determination of fetal sex, especially in X-linked disorders.

False positive amniotic fluid alpha fetoprotein levels resulting from contamination with fetal blood: results of an experiment.

The finding of an elevated level of alpha fetoprotein (AFP) in amniotic fluid is of value in the prenatal diagnosis of open neural tube defects. The present study was done to determine the amount of fetal blood required in amniotic fluid to produce a significant and misleading increase in AFP. Fetal blood was obtained at hysterotomy, and measured volumes were added to amniotic fluid samples. Bethe-Kleihauer tests, red cell counts, and AFP determinations were done. On the average, at 16 weeks' gestation, contamination of 5 ml. of amniotic fluid with 22 mul of fetal blood will results in an increase in AFP of 1.6 mg. per deciliter. Fetal cells in a much lower concentration can readily be detected by the Bethe-Kleihauer technique. A Bethe-Kleihauer test and red cell count should be done on all blood-stained amniotic fluid samples to determine the amount of fetal blood present. The contribution of the fetal blood AFP can then be estimated and must be considered in the interpretation of the total amniotic fluid AFP result.

The influence of smoking on the haemostatic mechanism in pregnancy.

A prospective study through pregnancy is described comparing smokers with non-smokers in an attempt to assess possible changes in the haemostatic mechanism. Various components of the coagulation and fibrinolytic enzyme systems were assayed serially up to 38 weeks of gestation. Plasma fibrinogen was lower in the smokers than in the non-smokers. Also plasminogen was slightly decreased and plasminogen activator activity and serum F.D.P. increased in the former group. Although the results failed to demonstrate motor disseminated intravascular coagulation in smokers, the pattern of a possible low grade syndrome emerged.

PIP: During pregnancy, 12 women who smoked more than 10 cigarettes/day and 12 nonsmokers had blood taken and analyzed at 12, 20, 25, 30, 34, and 38 weeks of gestation. Fibrinogen, plasminogen, plasminogen activator, serum fibrin degradation products, antithrombin 3, alpha 1 antitrypsin, and alpha 2 macroglobulin were measured. The only significant (p .05) difference was that plasma fibrinogen was lower among smokers at 20 weeks. However, there were other patterns of difference -- mean fibrinogen and plasminogen levels were slightly lower throughout pregnancy and reached a lower peak in the smoking group. Fibrinolytic activity fell in the smokers to the same low level as in nonsmokers by 38 weeks, but at a slower rate. Serum fibrin degradation products and alpha 2 macroglobulin were consistently higher in the smoking group. Although the findings showed no major disseminated intravascular coagulation in smokers, there was a pattern of a possible low-grade syndrome.

Changes preceding the development of preeclamptic toxemia.

No differences were found at the 30th week of pregnancy in total body water, serum sodium, potassium, chloride and osmolality, plasma volume, total protein concentration, intravascular protein mass, serum albumin concentration, intravascular albumin mass, and urinary estriol and pregnanediol in 94 primigravidae who remained normotensive, 35 who developed mild preeclampsia, and 23 who developed severe preeclampsia (i.e. hypertension and significant proteinuria in the third trimester). In twin pregnancies no differences were found between 13 primigravidae who remained normotensive and nine who subsequently developed proteinuria and hypertension.

The cause of the fall in serum folate in normal pregnancy.

Study of a complete antenatal population, a group of normal primigravid singleton pregnancies, and a group of normal twin pregnancies, suggests that the fall in the serum folate concentration which occurs in normal pregnancy is due principally to plasma volume expansion and should therefore be regarded as physiological.

The effect of plasma retransfusion on the blood pressure in the puerperium.

Whole blood was collected from five patients with severe pre-eclampsia, three with mild pre-eclampsia, and three with normal uneventful pregnancies. The red cells were separated and replaced. The plasma was stored until after the patients were delivered and on the sixth postpartum day they were autotransfused with plasma. This caused a rise in blood pressure in the patients with pre-eclampsia but an aliquot which was stored for six weeks and then retransfused into these patients did not cause any change in blood pressure. No blood pressure changes were found in the normal control subjects at six days or six weeks post partum. It is postulated that patients with pre-eclampsia develop altered vascular sensitivity to normal amounts of circulating pressor substance and that his sensitivity lasts for a week after delivery but not as long as six weeks.