Analysis of time of onset of NVP from first day of last menstrual period (LMP)




1.   Sickness of pregnancy sets in around the 40th day - Soranus, AD100. (10)

2.   363 women in study, mean day of onset of nausea, day 39 from LMP. (50)

3.   Symptoms of NVP began typically at four to six weeks gestation, 825 women in study.    (31)

4.   The mean and median week of onset of nausea among women who ever had nausea was the 6th week of gestation. No significant difference in mean days of onset for women    with nausea only, compared with women who had nausea and vomiting. 414 women in study. (21)

5.   71% of 43 women with HG started symptoms prior to the sixth week from LMP.    (7)

6.   Mean day of onset of NVP 5.6 ± 1.7 weeks of gestation. 260 women in study.    (91)

7.   Mean day of onset of NVP 5.5 weeks. 27 women in study. (103)

8.   The mean gestational age at onset was 5.7 weeks. 160 women in study. (80)




The mean day of onset of NVP day 39 from LMP. (Five references)

Pooled population 2092 women in 7 studies.




1.   8% of 500 women developed NVP before their first missed period. (27)

2.   20% of 414 women developed NVP before fourth week of gestation. (21)

3.   13.3% of 363 women developed NVP on or before day 28 from LMP. (50)

4.   16.2% of 43 patients with hyperemesis gravidarum started symptoms before day 28 from LMP i.e. before a missed period. (7)

5.   12.3%, 37 in 300 women, started NVP before they missed a period.

                                                                                    (Barnie-Adshead, not published)


Total number of women in five references = 1620.


Number whose NVP started before day 28 from LMP, 215 = 13.2%.


4c.            LATE ONSET OF NVP


1.   94% of 363 women started nausea on or before day 56 from LMP. (50)

2.   Nearly 80% of 414 women started nausea by day 56 from LMP. (21)

3.   87% of 500 women, nausea and vomiting had commenced by the eighth week of pregnancy. (27)

4.   11.6% of 43 women with HG started symptoms after eighth week of pregnancy. (7)

5.   Eight of 118 (6.7%) of women noted nausea beginning during or after week 10.
160 women in study. 90% of women destined to have NVP reported its onset by the eighth week of pregnancy. 160 women in study. (80)

6.   NVP began at less than six weeks from LMP for 90% of women and by the eighth week of pregnancy NVP had begun for all women. 593 women in study. (81)

7.   86.4% started NVP by day 56 from LMP. 55 women in study, 37 experienced NVP. (110)




90% of women who will get NVP start before day 56 from LMP.  (Seven references)

Pooled population in 7 studies 2036 women.




1.   Vomiting began as early as a gestational age (from LMP) of four weeks. (80)

2.   Forty per cent of total women in study (414) were experiencing vomiting by the eighth week (up to day 56 from LMP) compared to 70% experiencing nausea. (21)

3.   91.5% of 414 women had developed vomiting by 12th week of pregnancy. (21)




Vomiting often begins one or two weeks after nausea of NVP.




  1. Average number of hours of nausea for those women whose symptoms started on

         or before day 28 from LMP = 144.3 hours. (Total number of hours of nausea = 4,770

         in 33 women).

         Average number of hours of nausea for those women whose symptoms started on

         or after day 50 from LMP = 57.6 hours. (Total number of hours of nausea = 1,787

         in 31 women).

         Women whose NVP starts early, on or before day 28 from LMP, have more hours of NVP than those who start later, after day 50 from LMP. This result may be expected because whether nausea starts early or late from LMP, the symptoms cease at approximately the same time. (50)

 2.   Neither the time of onset during pregnancy, nor loss of weight indicates the severity of hyperemesis gravidarum nor affords a safeguard to its prognosis. 43 women with hyperemesis gravidarum in study. (7)

3.   Women who had early onset of vomiting or nausea after conception were more likely to experience daily sickness symptoms compared to those women who reported that the onset of their symptoms occurred later than seven weeks (i.e. after day 49) gestational age. 1,000 women in study. (Early onset worse symptoms). (40)

4.   NVP started at the same stage of gestation, 5.6 weeks, even though symptoms of NVP for the women in this study were more severe than the average in the population. 260 women in study population. (91)




Time of onset of NVP not related to the severity of symptoms. (7) (91)            Total 2 Refs.

Early onset of NVP associated with longer hours of nausea. (50) (40)            Total 2 Refs.




1.   In order to compare the symptoms of one woman’s pregnancy with that of another, the week of peak symptoms was plotted. The peak incidence was in weeks 7-9, median week 9 from LMP, inter-quartile weeks 8-10 after rising sharply from week 6.

         The tail-off is gradual after week 10. (50)

2.   The distribution of the proportion of women with nausea each week of gestation shows the peak at eight weeks, reflecting that fact that most women who ever had nausea had begun having symptoms by the eighth week and very few had ceased having symptoms by then. (21)
The distribution of the population of women having vomiting in each week of gestation peaked at about the same time as for nausea, but the peak was flatter for vomiting, reflecting the somewhat higher variance in week of onset of vomiting. (21)

3.   Although gestational age at which nausea was reported to be most severe varied, the weeks of peak severity occurred at 11 and 13 weeks from LMP. 160 women in study. Week 11 from LMP was the week in which the highest proportion women, 40%, had nausea. (80) Week 11 was also the peak week for vomiting.  (80).

4.   For the purpose of studying the variation in the weekly rate of N/V, the data from    medical records was used to determine the weekly acute nausea prescription rates. The rates for weeks 5-6 are based on small numbers; from week eight onward throughout the third lunar month, (12 weeks), the rate is almost constant. There is a slight suggestion of a small peak between 10 and 11 weeks from LMP.  Thereafter, the rate declines rapidly. 4,172 women entered the study within 12 weeks from LMP. (5)

5.   The patients in the trial had symptoms of relatively acute onset which were mainly of moderate severity. The treatment of nausea and vomiting most commonly started one or two weeks after the first symptoms commenced. 28 women. (17)

6.   Symptoms of NVP peaked in intensity between 8-12 weeks of gestation. 825 women in study. (31)




7.   Of women who completed the questionnaire (1,000 women in study) before 12 weeks of pregnancy (17% i.e. 170) 65% reported reduction in frequency of vomiting and 62% of nausea. (40)

8.   Only 9.3% of women experience NVP which gets worse by more than seven hours per week after the end of week nine (day 63) from LMP. (50)

9.   When comparing group time 1n = 306 gestation approx. 9 weeks with group time 2n = 231 gestation time mean 12.8 weeks a significant reduction was noted in severity of reported nausea. No significant difference in vomiting was noted. (156)




The evidence of these papers shows weeks 7-13 from LMP to be the weeks of maximum NVP. Most authors give a tighter two week period within this range. We believe weeks 7-9 from LMP to be the period of maximum NVP. (50)

Pooled population of 9 studies 6729 women.

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