Maternal plasma alpha-fetoprotein and low birthweight: a prospective study throughout pregnancy

Second-trimester maternal serum alpha-fetoprotein (MSAFP) is elevated in women with adverse pregnancy outcome associated with inherited thrombophilias

Obstetric complications, such as severe pre-eclampsia, fetal growth restriction, abruptio placentae, or stillbirth are associated with abnormally elevated second-trimester maternal serum alpha-fetoprotein (MSAFP) and beta subunit of human chorionic gonadotrophin (betahCG). This has been attributed to placental abnormalities. Women with thrombophilias have been shown to have abnormalities of the placenta resulting in adverse pregnancy outcome in these patients. The purpose of the present study was to evaluate whether women with pregnancy complications and inherited thrombophilias have abnormally elevated second-trimester MSAFP or betahCG. Sixty-two women with pregnancy complications were tested for inherited thrombophilias several months after delivery. The thrombophilia group included 29 women with pregnancy complications and an inherited thrombophilia and the control group included 33 other patients without thrombophilia. Patients in the thrombophilia group had a higher median MoM MSAFP compared to the controls (1.337 vs. 1.086, p=0.0516). The incidence of abnormally elevated MSAFP (>2.5 MoM) was also significantly higher in the thrombophilia group compared to controls (21% vs. 3%, p=0.04). Neither the median MoM betahCG nor the incidence of abnormally elevated betahCG were significantly different between the groups. We conclude that second trimester MSAFP, but not betahCG, is abnormally elevated in patients with thrombophilia and obstetric complications.

Unexplained elevated maternal serum alpha-fetoprotein: what is the appropriate follow-up?

Unexplained elevations of maternal serum alpha-fetoprotein exist in approximately 1% of the obstetric population. A consensus has been reached that these women face an increased risk of adverse pregnancy outcome. Whether their overall risk can be altered by the currently available surveillance modalities, however, remains controversial. Current research has focused on identifying those pregnancies with the highest risks of either fetal growth restriction, pre-eclampsia, preterm delivery or intrauterine fetal demise. Markedly increased maternal serum alpha-fetoprotein (over 4.0 multiples of the median), elevations of other serum markers such as human chorionic gonadotropin and abnormal umbilical Doppler flow are associated with the greatest risk of poor pregnancy outcome. When initiating surveillance of the pregnancy with unexplained elevated maternal serum alpha-fetoprotein consideration of these factors is receiving increased attention.

Routine testing and prophylaxis

Routine testing and prophylaxis is considered in terms of haematological disorders, biochemical testing, hormonal testing, screening for gestational diabetes and nutritional deficiencies. Within these headings the place of routine supplementation of pregnant women with iron, vitamins, trace elements and an increased protein/calorie intake is discussed. Screening for haemoglobinopathies, irregular blood group antibodies and gestational diabetes is dealt with in detail. The place for routine prophylaxis with anti-D is considered. Biochemical and hormonal testing is covered with particular reference to the use of biochemical and hormonal assays as placental function tests and their use in assessing fetal well-being. In this respect the use of biochemical and hormonal tests to screen a pregnant population for intrauterine growth retardation is also discussed.

Measurement of placental alkaline phosphatase in maternal plasma as an indicator of subsequent low birthweight outcome

Placental alkaline phosphatase (P-ALP) was measured by a specific monoclonal antibody-based immunoassay in plasma samples of 117 women who subsequently were delivered of an infant of birthweight less than 2.5 kg. P-ALP values greater than twice the normal median were found in 32% of maternal plasma samples from low birthweight cases in one series and in 35% in another series, while in normal outcome controls the corresponding value was 8%. The differences were highly significant. The proportion of low birthweight cases with elevated maternal P-ALP values appears to be very similar between 15 and 34 weeks gestation. At 16-18 weeks gestation there is a significant positive correlation (r = 0.40) between P-ALP and maternal plasma alpha-fetoprotein (AFP) values in low birthweight cases. The use of P-ALP assay in combination with AFP assay appears to improve the detection of pregnancies with subsequent low birthweight outcome.

Alpha-fetoprotein, vaginal bleeding and pregnancy risk

To assess the interrelation between maternal serum alpha-fetoprotein (MSAFP) levels and vaginal bleeding as a combined pregnancy risk factor, we studied 6829 singleton pregnancies without fetal malformations during the second trimester. The predictive powers of the two risk factors, analysed separately, are consistent with published reports in relation to fetal death and low birthweight. Until now, however, these two risk factors have not been analysed together. The present study demonstrates that MSAFP and vaginal bleeding are largely independent of each other as predictors of fetal death, relative risks being 0.7 (MSAFP less than 0.7 multiples of the median (MoM), vaginal bleeding absent), 3.5 (MSAFP less than 2.0 MoM vaginal bleeding present), 5.8 (MSAFP greater than or equal to 2.0 MoM, vaginal bleeding absent), and 12.6 (MSAFP greater than or equal to 2.0 MoM, vaginal bleeding present). Corresponding risks for low birthweight are: 0.7, 1.8, 2.5 and 1.6 (mean birthweights in the four categories are 3516 g, 3407 g, 3238 g, and 3176 g).

Factors influencing birthweight for gestational age, with special respect to risk factors for intrauterine growth retardation

In a prospective clinical study from an unselected, area-based population, the influence on birthweight for gestational age of different factors was studied, with special respect to 15 risk factors for intrauterine growth retardation (IUGR) recognizable in early pregnancy. In the multiple regression analyses performed, birthweight for gestational age was used as the dependent variable. Only 10% of the variance in birthweight for gestational age could be explained. A correlation was found between the number of risk factors and birthweight for gestational age. Four risk factors had a significant negative influence on birthweight for gestational age: smoking, previous birth of a low birthweight infant, a low prepregnancy weight and addiction. No single risk factor influenced birthweight for gestational age as much as parity. When a risk factor was present the expected increase in birthweight for gestational age with increasing parity did not appear.

Early pregnancy screening for intrauterine growth retardation

In a prospective clinical study from Uppsala County, Sweden, in 1980, all pregnancies were screened early in pregnancy for 15 previously reported risk factors for intrauterine growth retardation (IUGR). This risk group (n = 639) was then compared with a randomly selected control group (n = 539). In the risk group, there were increased risks for the delivery of growth retarded infants, low birthweight infants and infants spontaneously delivered as prematures. 30% of the population exhibited risk factors. Smoking was the most important risk factor, 16% of the mothers smoked at least ten cigarettes per day and smoking was the main risk factor in the majority of cases with IUGR.